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Spring Boot 集成 Redisson分布式锁

Jonescy 2023-06-24 阅读 72
javajava-ee

Java反射机制概述

前言

本博主将用CSDN记录软件开发求学之路上亲身所得与所学的心得与知识，有兴趣的小伙伴可以关注博主！
也许一个人独行，可以走的很快，但是一群人结伴而行，才能走的更远！让我们在成长的道路上互相学习，欢迎关注！

一、Java反射机制概述

1. Java Reflection

2. 动态语言 vs 静态语言

（1）动态语言

（2）静态语言

（3）Java反射机制研究及应用

二、 Class类的理解

1. 类的加载过程

1.1 初步了解

1.2 类的加载过程图解

在这里插入图片描述

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java"><span style="color:#ff79c6">public</span> <span style="color:#ff79c6">class</span> ClassLoadingTest <span style="color:#999999">{</span>
<span style="color:#ff79c6">public</span> <span style="color:#ff79c6">static</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">main</span><span style="color:#999999">(</span>String<span style="color:#999999">[</span><span style="color:#999999">]</span> args<span style="color:#999999">)</span> <span style="color:#999999">{</span>
System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>A<span style="color:#999999">.</span>m<span style="color:#999999">)</span><span style="color:#999999">;</span>
<span style="color:#999999">}</span> <span style="color:#999999">}</span>
<span style="color:#ff79c6">class</span> A <span style="color:#999999">{</span>
<span style="color:#ff79c6">static</span> <span style="color:#999999">{</span> m <span style="color:#6272a4">=</span> <span style="color:#f1fa8c">300</span><span style="color:#999999">;</span>
<span style="color:#999999">}</span>
<span style="color:#ff79c6">static</span> <span style="color:#ff79c6">int</span> m <span style="color:#6272a4">=</span> <span style="color:#f1fa8c">100</span><span style="color:#999999">;</span>
<span style="color:#999999">}</span>
<span style="color:#6272a4">//第二步：链接结束后m=0</span>
<span style="color:#6272a4">//第三步：初始化后，m的值由<clinit>()方法执行决定</span>
<span style="color:#6272a4">// 这个A的类构造器<clinit>()方法由类变量的赋值和静态代码块中的语句按照顺序合并产生，类似于</span>
<span style="color:#6272a4">// <clinit>(){</span>
<span style="color:#6272a4">// m = 300;</span>
<span style="color:#6272a4">// m = 100;</span>
<span style="color:#6272a4">// }</span>
</code></span></span></span>

1.3 了解：什么时候会发生类初始化？

1.4 类加载器的作用

在这里插入图片描述

1.5 JVM中不同类型的类的加载器

在这里插入图片描述

1.6 代码演示

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java"> <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test1</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        <span style="color:#6272a4">//对于自定义类，使用系统类加载器进行加载</span>
        ClassLoader classLoader <span style="color:#6272a4">=</span> ClassLoaderTest<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">.</span><span style="color:#8be9fd">getClassLoader</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>classLoader<span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//sun.misc.Launcher$AppClassLoader@18b4aac2:系统类加载器</span>
        <span style="color:#6272a4">//调用系统类加载器的getParent()：获取扩展类加载器</span>
        ClassLoader classLoader1 <span style="color:#6272a4">=</span> classLoader<span style="color:#999999">.</span><span style="color:#8be9fd">getParent</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>classLoader1<span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//sun.misc.Launcher$ExtClassLoader@279f2327：扩展类加载器</span>
        <span style="color:#6272a4">//调用扩展类加载器的getParent()：无法获取引导类加载器</span>
        <span style="color:#6272a4">//引导类加载器主要负责加载java的核心类库，无法加载自定义类的。</span>
        ClassLoader classLoader2 <span style="color:#6272a4">=</span> classLoader1<span style="color:#999999">.</span><span style="color:#8be9fd">getParent</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>classLoader2<span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//null</span>

        ClassLoader classLoader3 <span style="color:#6272a4">=</span> String<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">.</span><span style="color:#8be9fd">getClassLoader</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>classLoader3<span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//null</span>

    <span style="color:#999999">}</span>
</code></span></span></span>

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java"> <span style="color:#6272a4">/*
    Properties：用来读取配置文件。

     */</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test2</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#ff79c6">throws</span> Exception <span style="color:#999999">{</span>

        Properties pros <span style="color:#6272a4">=</span>  <span style="color:#ff79c6">new</span> Properties<span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#6272a4">//此时的文件默认在当前的module下。</span>
        <span style="color:#6272a4">//读取配置文件的方式一：</span>
<span style="color:#6272a4">//        FileInputStream fis = new FileInputStream("jdbc.properties");</span>
<span style="color:#6272a4">//        FileInputStream fis = new FileInputStream("src\\jdbc1.properties");</span>
<span style="color:#6272a4">//        pros.load(fis);</span>

        <span style="color:#6272a4">//读取配置文件的方式二：使用ClassLoader</span>
        <span style="color:#6272a4">//配置文件默认识别为：当前module的src下</span>
        ClassLoader classLoader <span style="color:#6272a4">=</span> ClassLoaderTest<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">.</span><span style="color:#8be9fd">getClassLoader</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        InputStream is <span style="color:#6272a4">=</span> classLoader<span style="color:#999999">.</span><span style="color:#8be9fd">getResourceAsStream</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"jdbc1.properties"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        pros<span style="color:#999999">.</span><span style="color:#8be9fd">load</span><span style="color:#999999">(</span>is<span style="color:#999999">)</span><span style="color:#999999">;</span>


        String user <span style="color:#6272a4">=</span> pros<span style="color:#999999">.</span><span style="color:#8be9fd">getProperty</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"user"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        String password <span style="color:#6272a4">=</span> pros<span style="color:#999999">.</span><span style="color:#8be9fd">getProperty</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"password"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"user = "</span> <span style="color:#6272a4">+</span> user <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">",password = "</span> <span style="color:#6272a4">+</span> password<span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>
<span style="color:#999999">}</span>
</code></span></span></span>

2. 何为Class类？

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java"><span style="color:#ff79c6">public</span> <span style="color:#ff79c6">final</span> Class <span style="color:#8be9fd">getClass</span><span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span>

在这里插入图片描述

3. Class类的常用方法方法

方法名功能说明
static Class forName(String name)返回指定类名 name 的 Class 对象
Object newInstance()调用缺省构造函数，返回该Class对象的一个实例
getName()返回此Class对象所表示的实体（类、接口、数组类、基本类型或void）名称
Class getSuperClass()返回当前Class对象的父类的Class对象
Class [] getInterfaces()获取当前Class对象的接口
ClassLoader getClassLoader()返回该类的类加载器
Class getSuperclass()返回表示此Class所表示的实体的超类的Class
Constructor[] getConstructors()返回一个包含某些Constructor对象的数组
Field[] getDeclaredFields()返回Field对象的一个数组
Method getMethod(String name,Class … paramTypes)返回一个Method对象，此对象的形参类型为paramType

3. 哪些类型可以有Class对象？

三、获取Class类实例的四种方法

1. 调用运行时类的属性：.class

2. 通过运行时类的对象,调用getClass()

3.调用Class的静态方法：forName(String classPath)

4. 使用类的加载器：ClassLoader

5. 代码演示

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java"><span style="color:#999999">@Test</span>
<span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test1</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#ff79c6">throws</span> ClassNotFoundException <span style="color:#999999">{</span>
            <span style="color:#6272a4">//方式一：调用运行时类的属性：.class</span>
            Class clazz1 <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>clazz1<span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//class com.jiaying.java1.Person</span>
            <span style="color:#6272a4">//方式二：通过运行时类的对象,调用getClass()</span>
            Person p1 <span style="color:#6272a4">=</span> <span style="color:#ff79c6">new</span> Person<span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            Class clazz2 <span style="color:#6272a4">=</span> p1<span style="color:#999999">.</span><span style="color:#8be9fd">getClass</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>clazz2<span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//class com.jiaying.java1.Person</span>

            <span style="color:#6272a4">//方式三：调用Class的静态方法：forName(String classPath)</span>
            Class clazz3 <span style="color:#6272a4">=</span> Class<span style="color:#999999">.</span><span style="color:#8be9fd">forName</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"com.jiaying.java1.Person"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            Class clazz5 <span style="color:#6272a4">=</span> Class<span style="color:#999999">.</span><span style="color:#8be9fd">forName</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"java.lang.String"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>clazz3<span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//class com.jiaying.java1.Person</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>clazz5<span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//class java.lang.String</span>

            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>clazz1 <span style="color:#6272a4">==</span> clazz2<span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//true</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>clazz1 <span style="color:#6272a4">==</span> clazz3<span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//true</span>

            <span style="color:#6272a4">//方式四：使用类的加载器：ClassLoader  (了解)</span>
            ClassLoader classLoader <span style="color:#6272a4">=</span> ReflectionTest<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">.</span><span style="color:#8be9fd">getClassLoader</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            Class clazz4 <span style="color:#6272a4">=</span> classLoader<span style="color:#999999">.</span><span style="color:#8be9fd">loadClass</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"com.jiaying.java1.Person"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>clazz4<span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//class com.jiaying.java1.Person</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>clazz1 <span style="color:#6272a4">==</span> clazz4<span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//true</span>
<span style="color:#999999">}</span>
</code></span></span></span>

四、 创建运行时类的对象

1. 引入

2. 语法步骤

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java">String name <span style="color:#6272a4">=</span> “atguigu<span style="color:#999999">.</span>java<span style="color:#999999">.</span>Person"<span style="color:#999999">;</span>
Class clazz <span style="color:#6272a4">=</span> <span style="color:#ff79c6">null</span><span style="color:#999999">;</span>
clazz <span style="color:#6272a4">=</span> Class<span style="color:#999999">.</span><span style="color:#8be9fd">forName</span><span style="color:#999999">(</span>name<span style="color:#999999">)</span><span style="color:#999999">;</span>
</code></span></span></span>

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java">Constructor con <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getConstructor</span><span style="color:#999999">(</span>String<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">,</span>Integer<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
</code></span></span></span>
<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java">Person p2 <span style="color:#6272a4">=</span> <span style="color:#999999">(</span>Person<span style="color:#999999">)</span> con<span style="color:#999999">.</span><span style="color:#8be9fd">newInstance</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"Peter"</span><span style="color:#999999">,</span><span style="color:#f1fa8c">20</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>p2<span style="color:#999999">)</span><span style="color:#999999">;</span>
</code></span></span></span>

3. 代码演示

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java"> <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test1</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#ff79c6">throws</span> IllegalAccessException<span style="color:#999999">,</span> InstantiationException <span style="color:#999999">{</span>

        Class<span style="color:#999999"><</span>Person<span style="color:#999999">></span> clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>
        <span style="color:#6272a4">/*
        newInstance():调用此方法，创建对应的运行时类的对象。内部调用了运行时类的空参的构造器。

        要想此方法正常的创建运行时类的对象，要求：
        1.运行时类必须提供空参的构造器
        2.空参的构造器的访问权限得够。通常，设置为public。


        在javabean中要求提供一个public的空参构造器。原因：
        1.便于通过反射，创建运行时类的对象
        2.便于子类继承此运行时类时，默认调用super()时，保证父类有此构造器

         */</span>
        Person obj <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">newInstance</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>obj<span style="color:#999999">)</span><span style="color:#999999">;</span>

    <span style="color:#999999">}</span>

</code></span></span></span>

4. 体会反射的动态性

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java"><span style="color:#6272a4">//体会反射的动态性</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test2</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>

        <span style="color:#ff79c6">for</span><span style="color:#999999">(</span><span style="color:#ff79c6">int</span> i <span style="color:#6272a4">=</span> <span style="color:#f1fa8c">0</span><span style="color:#999999">;</span>i <span style="color:#6272a4"><</span> <span style="color:#f1fa8c">100</span><span style="color:#999999">;</span>i<span style="color:#6272a4">++</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
            <span style="color:#ff79c6">int</span> num <span style="color:#6272a4">=</span> <span style="color:#ff79c6">new</span> Random<span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">.</span><span style="color:#8be9fd">nextInt</span><span style="color:#999999">(</span><span style="color:#f1fa8c">3</span><span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//0,1,2</span>
            String classPath <span style="color:#6272a4">=</span> <span style="color:#f1fa8c">""</span><span style="color:#999999">;</span>
            <span style="color:#ff79c6">switch</span><span style="color:#999999">(</span>num<span style="color:#999999">)</span><span style="color:#999999">{</span>
                <span style="color:#ff79c6">case</span> <span style="color:#f1fa8c">0</span><span style="color:#6272a4">:</span>
                    classPath <span style="color:#6272a4">=</span> <span style="color:#f1fa8c">"java.util.Date"</span><span style="color:#999999">;</span>
                    <span style="color:#ff79c6">break</span><span style="color:#999999">;</span>
                <span style="color:#ff79c6">case</span> <span style="color:#f1fa8c">1</span><span style="color:#6272a4">:</span>
                    classPath <span style="color:#6272a4">=</span> <span style="color:#f1fa8c">"java.lang.Object"</span><span style="color:#999999">;</span>
                    <span style="color:#ff79c6">break</span><span style="color:#999999">;</span>
                <span style="color:#ff79c6">case</span> <span style="color:#f1fa8c">2</span><span style="color:#6272a4">:</span>
                    classPath <span style="color:#6272a4">=</span> <span style="color:#f1fa8c">"com.atguigu.java.Person"</span><span style="color:#999999">;</span>
                    <span style="color:#ff79c6">break</span><span style="color:#999999">;</span>
            <span style="color:#999999">}</span>

            <span style="color:#ff79c6">try</span> <span style="color:#999999">{</span>
                Object obj <span style="color:#6272a4">=</span> <span style="color:#8be9fd">getInstance</span><span style="color:#999999">(</span>classPath<span style="color:#999999">)</span><span style="color:#999999">;</span>
                System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>obj<span style="color:#999999">)</span><span style="color:#999999">;</span>
            <span style="color:#999999">}</span> <span style="color:#ff79c6">catch</span> <span style="color:#999999">(</span>Exception e<span style="color:#999999">)</span> <span style="color:#999999">{</span>
                e<span style="color:#999999">.</span><span style="color:#8be9fd">printStackTrace</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            <span style="color:#999999">}</span>
        <span style="color:#999999">}</span>
    <span style="color:#999999">}</span>

    <span style="color:#6272a4">/*
    创建一个指定类的对象。
    classPath:指定类的全类名
     */</span>
    <span style="color:#ff79c6">public</span> Object <span style="color:#8be9fd">getInstance</span><span style="color:#999999">(</span>String classPath<span style="color:#999999">)</span> <span style="color:#ff79c6">throws</span> Exception <span style="color:#999999">{</span>
       Class clazz <span style="color:#6272a4">=</span>  Class<span style="color:#999999">.</span><span style="color:#8be9fd">forName</span><span style="color:#999999">(</span>classPath<span style="color:#999999">)</span><span style="color:#999999">;</span>
       <span style="color:#ff79c6">return</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">newInstance</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>
<span style="color:#999999">}</span>
</code></span></span></span>

五、获取运行时类的完整结构

提供具有丰富内容的Person类

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java"><span style="color:#6272a4">//接口</span>
<span style="color:#ff79c6">public</span> <span style="color:#ff79c6">interface</span> MyInterface <span style="color:#999999">{</span>
    <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">info</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
<span style="color:#999999">}</span>

<span style="color:#6272a4">//注解</span>
<span style="color:#999999">@Target</span><span style="color:#999999">(</span><span style="color:#999999">{</span>TYPE<span style="color:#999999">,</span> FIELD<span style="color:#999999">,</span> METHOD<span style="color:#999999">,</span> PARAMETER<span style="color:#999999">,</span> CONSTRUCTOR<span style="color:#999999">,</span> LOCAL_VARIABLE<span style="color:#999999">}</span><span style="color:#999999">)</span>
<span style="color:#999999">@Retention</span><span style="color:#999999">(</span>RetentionPolicy<span style="color:#999999">.</span>RUNTIME<span style="color:#999999">)</span>
<span style="color:#ff79c6">public</span> <span style="color:#999999">@interface</span> MyAnnotation <span style="color:#999999">{</span>
    String <span style="color:#8be9fd">value</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#ff79c6">default</span> <span style="color:#f1fa8c">"hello"</span><span style="color:#999999">;</span>

<span style="color:#999999">}</span>

<span style="color:#6272a4">//父类</span>
<span style="color:#ff79c6">public</span> <span style="color:#ff79c6">class</span> Creature<span style="color:#999999"><</span>T<span style="color:#999999">></span> <span style="color:#ff79c6">implements</span> Serializable <span style="color:#999999">{</span>
    <span style="color:#ff79c6">private</span> <span style="color:#ff79c6">char</span> gender<span style="color:#999999">;</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">double</span> weight<span style="color:#999999">;</span>

    <span style="color:#ff79c6">private</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">breath</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"生物呼吸"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>

    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">eat</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"生物吃东西"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>

<span style="color:#999999">}</span>

<span style="color:#6272a4">//Person类</span>
<span style="color:#999999">@MyAnnotation</span><span style="color:#999999">(</span>value<span style="color:#6272a4">=</span><span style="color:#f1fa8c">"hi"</span><span style="color:#999999">)</span>
<span style="color:#ff79c6">public</span> <span style="color:#ff79c6">class</span> Person <span style="color:#ff79c6">extends</span> Creature<span style="color:#999999"><</span>String<span style="color:#999999">></span> <span style="color:#ff79c6">implements</span> Comparable<span style="color:#999999"><</span>String<span style="color:#999999">></span><span style="color:#999999">,</span>MyInterface<span style="color:#999999">{</span>

    <span style="color:#ff79c6">private</span> String name<span style="color:#999999">;</span>
    <span style="color:#ff79c6">int</span> age<span style="color:#999999">;</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">int</span> id<span style="color:#999999">;</span>

    <span style="color:#ff79c6">public</span> Person<span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span><span style="color:#999999">}</span>

    <span style="color:#999999">@MyAnnotation</span><span style="color:#999999">(</span>value<span style="color:#6272a4">=</span><span style="color:#f1fa8c">"abc"</span><span style="color:#999999">)</span>
    <span style="color:#ff79c6">private</span> Person<span style="color:#999999">(</span>String name<span style="color:#999999">)</span><span style="color:#999999">{</span>
        <span style="color:#ff79c6">this</span><span style="color:#999999">.</span>name <span style="color:#6272a4">=</span> name<span style="color:#999999">;</span>
    <span style="color:#999999">}</span>

     Person<span style="color:#999999">(</span>String name<span style="color:#999999">,</span><span style="color:#ff79c6">int</span> age<span style="color:#999999">)</span><span style="color:#999999">{</span>
        <span style="color:#ff79c6">this</span><span style="color:#999999">.</span>name <span style="color:#6272a4">=</span> name<span style="color:#999999">;</span>
        <span style="color:#ff79c6">this</span><span style="color:#999999">.</span>age <span style="color:#6272a4">=</span> age<span style="color:#999999">;</span>
    <span style="color:#999999">}</span>
    <span style="color:#999999">@MyAnnotation</span>
    <span style="color:#ff79c6">private</span> String <span style="color:#8be9fd">show</span><span style="color:#999999">(</span>String nation<span style="color:#999999">)</span><span style="color:#999999">{</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"我的国籍是："</span> <span style="color:#6272a4">+</span> nation<span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#ff79c6">return</span> nation<span style="color:#999999">;</span>
    <span style="color:#999999">}</span>

    <span style="color:#ff79c6">public</span> String <span style="color:#8be9fd">display</span><span style="color:#999999">(</span>String interests<span style="color:#999999">,</span><span style="color:#ff79c6">int</span> age<span style="color:#999999">)</span> <span style="color:#ff79c6">throws</span> NullPointerException<span style="color:#999999">,</span>ClassCastException<span style="color:#999999">{</span>
        <span style="color:#ff79c6">return</span> interests <span style="color:#6272a4">+</span> age<span style="color:#999999">;</span>
    <span style="color:#999999">}</span>


    <span style="color:#999999">@Override</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">info</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#999999">{</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"我是一个人"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>

    <span style="color:#999999">@Override</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">int</span> <span style="color:#8be9fd">compareTo</span><span style="color:#999999">(</span>String o<span style="color:#999999">)</span> <span style="color:#999999">{</span>
        <span style="color:#ff79c6">return</span> <span style="color:#f1fa8c">0</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>

    <span style="color:#ff79c6">private</span> <span style="color:#ff79c6">static</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">showDesc</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"我是一个可爱的人"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>

    <span style="color:#999999">@Override</span>
    <span style="color:#ff79c6">public</span> String <span style="color:#8be9fd">toString</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#999999">{</span>
        <span style="color:#ff79c6">return</span> <span style="color:#f1fa8c">"Person{"</span> <span style="color:#6272a4">+</span>
                <span style="color:#f1fa8c">"name='"</span> <span style="color:#6272a4">+</span> name <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">'\''</span> <span style="color:#6272a4">+</span>
                <span style="color:#f1fa8c">", age="</span> <span style="color:#6272a4">+</span> age <span style="color:#6272a4">+</span>
                <span style="color:#f1fa8c">", id="</span> <span style="color:#6272a4">+</span> id <span style="color:#6272a4">+</span>
                <span style="color:#f1fa8c">'}'</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>
<span style="color:#999999">}</span>
</code></span></span></span>

1. 获取当前运行时类的属性结构

方法作用
public Field[] getFields()返回此Class对象所表示的类或接口的public的Field
public Field[] getDeclaredFields()返回此Class对象所表示的类或接口的全部Field

  • Field方法中：

方法作用
public int getModifiers()以整数形式返回此Field的修饰符
public Class<?> getType()得到Field的属性类型
public String getName()返回Field的名称

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java">    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test1</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>

        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">//获取属性结构</span>
        <span style="color:#6272a4">//getFields():获取当前运行时类及其父类中声明为public访问权限的属性</span>
        Field<span style="color:#999999">[</span><span style="color:#999999">]</span> fields <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getFields</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#ff79c6">for</span><span style="color:#999999">(</span>Field f <span style="color:#6272a4">:</span> fields<span style="color:#999999">)</span><span style="color:#999999">{</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>f<span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#999999">}</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">//getDeclaredFields():获取当前运行时类中声明的所有属性。（不包含父类中声明的属性）</span>
        Field<span style="color:#999999">[</span><span style="color:#999999">]</span> declaredFields <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getDeclaredFields</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#ff79c6">for</span><span style="color:#999999">(</span>Field f <span style="color:#6272a4">:</span> declaredFields<span style="color:#999999">)</span><span style="color:#999999">{</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>f<span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#999999">}</span>
    <span style="color:#999999">}</span>

    <span style="color:#6272a4">//权限修饰符  数据类型 变量名</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test2</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>
        Field<span style="color:#999999">[</span><span style="color:#999999">]</span> declaredFields <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getDeclaredFields</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#ff79c6">for</span><span style="color:#999999">(</span>Field f <span style="color:#6272a4">:</span> declaredFields<span style="color:#999999">)</span><span style="color:#999999">{</span>
            <span style="color:#6272a4">//1.权限修饰符</span>
            <span style="color:#ff79c6">int</span> modifier <span style="color:#6272a4">=</span> f<span style="color:#999999">.</span><span style="color:#8be9fd">getModifiers</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">print</span><span style="color:#999999">(</span>Modifier<span style="color:#999999">.</span><span style="color:#8be9fd">toString</span><span style="color:#999999">(</span>modifier<span style="color:#999999">)</span> <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">"\t"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

            <span style="color:#6272a4">//2.数据类型</span>
            Class type <span style="color:#6272a4">=</span> f<span style="color:#999999">.</span><span style="color:#8be9fd">getType</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">print</span><span style="color:#999999">(</span>type<span style="color:#999999">.</span><span style="color:#8be9fd">getName</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">"\t"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

            <span style="color:#6272a4">//3.变量名</span>
            String fName <span style="color:#6272a4">=</span> f<span style="color:#999999">.</span><span style="color:#8be9fd">getName</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">print</span><span style="color:#999999">(</span>fName<span style="color:#999999">)</span><span style="color:#999999">;</span>

            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#999999">}</span>
    <span style="color:#999999">}</span>
<span style="color:#999999">}</span>

</code></span></span></span>

2. 获取当前运行时类的方法结构

方法作用
public Method[] getMethods()返回此Class对象所表示的类或接口的public的方法
public Method[] getDeclaredMethods()返回此Class对象所表示的类或接口的全部方法

  • Method类中：

方法作用
public Class<?> getReturnType()取得全部的返回值
public Class<?>[] getParameterTypes()取得全部的参数
public int getModifiers()取得修饰符
public Class<?>[] getExceptionTypes()取得异常信息

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java">    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test1</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>

        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">//getMethods():获取当前运行时类及其所有父类中声明为public权限的方法</span>
        Method<span style="color:#999999">[</span><span style="color:#999999">]</span> methods <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getMethods</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#ff79c6">for</span><span style="color:#999999">(</span>Method m <span style="color:#6272a4">:</span> methods<span style="color:#999999">)</span><span style="color:#999999">{</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>m<span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#999999">}</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#6272a4">//getDeclaredMethods():获取当前运行时类中声明的所有方法。（不包含父类中声明的方法）</span>
        Method<span style="color:#999999">[</span><span style="color:#999999">]</span> declaredMethods <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getDeclaredMethods</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#ff79c6">for</span><span style="color:#999999">(</span>Method m <span style="color:#6272a4">:</span> declaredMethods<span style="color:#999999">)</span><span style="color:#999999">{</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>m<span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#999999">}</span>
    <span style="color:#999999">}</span>
  <span style="color:#6272a4">/*
    @Xxxx
    权限修饰符  返回值类型  方法名(参数类型1 形参名1,...) throws XxxException{}
     */</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test2</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>
        Method<span style="color:#999999">[</span><span style="color:#999999">]</span> declaredMethods <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getDeclaredMethods</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#ff79c6">for</span><span style="color:#999999">(</span>Method m <span style="color:#6272a4">:</span> declaredMethods<span style="color:#999999">)</span><span style="color:#999999">{</span>
            <span style="color:#6272a4">//1.获取方法声明的注解</span>
            Annotation<span style="color:#999999">[</span><span style="color:#999999">]</span> annos <span style="color:#6272a4">=</span> m<span style="color:#999999">.</span><span style="color:#8be9fd">getAnnotations</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            <span style="color:#ff79c6">for</span><span style="color:#999999">(</span>Annotation a <span style="color:#6272a4">:</span> annos<span style="color:#999999">)</span><span style="color:#999999">{</span>
                System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>a<span style="color:#999999">)</span><span style="color:#999999">;</span>
            <span style="color:#999999">}</span>

            <span style="color:#6272a4">//2.权限修饰符</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">print</span><span style="color:#999999">(</span>Modifier<span style="color:#999999">.</span><span style="color:#8be9fd">toString</span><span style="color:#999999">(</span>m<span style="color:#999999">.</span><span style="color:#8be9fd">getModifiers</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">)</span> <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">"\t"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

            <span style="color:#6272a4">//3.返回值类型</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">print</span><span style="color:#999999">(</span>m<span style="color:#999999">.</span><span style="color:#8be9fd">getReturnType</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">.</span><span style="color:#8be9fd">getName</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">"\t"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

            <span style="color:#6272a4">//4.方法名</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">print</span><span style="color:#999999">(</span>m<span style="color:#999999">.</span><span style="color:#8be9fd">getName</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"("</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            <span style="color:#6272a4">//5.形参列表</span>
            Class<span style="color:#999999">[</span><span style="color:#999999">]</span> parameterTypes <span style="color:#6272a4">=</span> m<span style="color:#999999">.</span><span style="color:#8be9fd">getParameterTypes</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            <span style="color:#ff79c6">if</span><span style="color:#999999">(</span><span style="color:#6272a4">!</span><span style="color:#999999">(</span>parameterTypes <span style="color:#6272a4">==</span> <span style="color:#ff79c6">null</span> <span style="color:#6272a4">&&</span> parameterTypes<span style="color:#999999">.</span>length <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">0</span><span style="color:#999999">)</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
                <span style="color:#ff79c6">for</span><span style="color:#999999">(</span><span style="color:#ff79c6">int</span> i <span style="color:#6272a4">=</span> <span style="color:#f1fa8c">0</span><span style="color:#999999">;</span>i <span style="color:#6272a4"><</span> parameterTypes<span style="color:#999999">.</span>length<span style="color:#999999">;</span>i<span style="color:#6272a4">++</span><span style="color:#999999">)</span><span style="color:#999999">{</span>

                    <span style="color:#ff79c6">if</span><span style="color:#999999">(</span>i <span style="color:#6272a4">==</span> parameterTypes<span style="color:#999999">.</span>length <span style="color:#6272a4">-</span> <span style="color:#f1fa8c">1</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
                        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">print</span><span style="color:#999999">(</span>parameterTypes<span style="color:#999999">[</span>i<span style="color:#999999">]</span><span style="color:#999999">.</span><span style="color:#8be9fd">getName</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">" args_"</span> <span style="color:#6272a4">+</span> i<span style="color:#999999">)</span><span style="color:#999999">;</span>
                        <span style="color:#ff79c6">break</span><span style="color:#999999">;</span>
                    <span style="color:#999999">}</span>

                    System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">print</span><span style="color:#999999">(</span>parameterTypes<span style="color:#999999">[</span>i<span style="color:#999999">]</span><span style="color:#999999">.</span><span style="color:#8be9fd">getName</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">" args_"</span> <span style="color:#6272a4">+</span> i <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">","</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
                <span style="color:#999999">}</span>
            <span style="color:#999999">}</span>

            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">")"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

            <span style="color:#6272a4">//6.抛出的异常</span>
            Class<span style="color:#999999">[</span><span style="color:#999999">]</span> exceptionTypes <span style="color:#6272a4">=</span> m<span style="color:#999999">.</span><span style="color:#8be9fd">getExceptionTypes</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
            <span style="color:#ff79c6">if</span><span style="color:#999999">(</span>exceptionTypes<span style="color:#999999">.</span>length <span style="color:#6272a4">></span> <span style="color:#f1fa8c">0</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
                System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"throws "</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
                <span style="color:#ff79c6">for</span><span style="color:#999999">(</span><span style="color:#ff79c6">int</span> i <span style="color:#6272a4">=</span> <span style="color:#f1fa8c">0</span><span style="color:#999999">;</span>i <span style="color:#6272a4"><</span> exceptionTypes<span style="color:#999999">.</span>length<span style="color:#999999">;</span>i<span style="color:#6272a4">++</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
                    <span style="color:#ff79c6">if</span><span style="color:#999999">(</span>i <span style="color:#6272a4">==</span> exceptionTypes<span style="color:#999999">.</span>length <span style="color:#6272a4">-</span> <span style="color:#f1fa8c">1</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
                        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">print</span><span style="color:#999999">(</span>exceptionTypes<span style="color:#999999">[</span>i<span style="color:#999999">]</span><span style="color:#999999">.</span><span style="color:#8be9fd">getName</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
                        <span style="color:#ff79c6">break</span><span style="color:#999999">;</span>
                    <span style="color:#999999">}</span>

                    System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">print</span><span style="color:#999999">(</span>exceptionTypes<span style="color:#999999">[</span>i<span style="color:#999999">]</span><span style="color:#999999">.</span><span style="color:#8be9fd">getName</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">","</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
                <span style="color:#999999">}</span>
            <span style="color:#999999">}</span>


            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#999999">}</span>



    <span style="color:#999999">}</span>
<span style="color:#999999">}</span>

</code></span></span></span>

3. 获取当前运行时类的构造器结构

方法作用
public Constructor<T>[] getConstructors()返回此 Class 对象所表示的类的所有public构造方法。
public Constructor<T>[] getDeclaredConstructors()返回此 Class 对象表示的类声明的所有构造方法。

  • Constructor类中：

方法作用
public int getModifiers()取得修饰符
public String getName()取得方法名称
public Class<?>[] getParameterTypes()取得参数的类型

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java"><span style="color:#6272a4">/*
    获取构造器结构

     */</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test1</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>

        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>
        <span style="color:#6272a4">//getConstructors():获取当前运行时类中声明为public的构造器</span>
        Constructor<span style="color:#999999">[</span><span style="color:#999999">]</span> constructors <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getConstructors</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#ff79c6">for</span><span style="color:#999999">(</span>Constructor c <span style="color:#6272a4">:</span> constructors<span style="color:#999999">)</span><span style="color:#999999">{</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>c<span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#999999">}</span>

        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#6272a4">//getDeclaredConstructors():获取当前运行时类中声明的所有的构造器</span>
        Constructor<span style="color:#999999">[</span><span style="color:#999999">]</span> declaredConstructors <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getDeclaredConstructors</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#ff79c6">for</span><span style="color:#999999">(</span>Constructor c <span style="color:#6272a4">:</span> declaredConstructors<span style="color:#999999">)</span><span style="color:#999999">{</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>c<span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#999999">}</span>

    <span style="color:#999999">}</span>
 <span style="color:#6272a4">/*
    获取运行时类的父类

     */</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test2</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>

        Class superclass <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getSuperclass</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>superclass<span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>

    <span style="color:#6272a4">/*
    获取运行时类的带泛型的父类

     */</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test3</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>

        Type genericSuperclass <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getGenericSuperclass</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>genericSuperclass<span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>

    <span style="color:#6272a4">/*
    获取运行时类的带泛型的父类的泛型


    代码：逻辑性代码  vs 功能性代码
     */</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test4</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>

        Type genericSuperclass <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getGenericSuperclass</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        ParameterizedType paramType <span style="color:#6272a4">=</span> <span style="color:#999999">(</span>ParameterizedType<span style="color:#999999">)</span> genericSuperclass<span style="color:#999999">;</span>
        <span style="color:#6272a4">//获取泛型类型</span>
        Type<span style="color:#999999">[</span><span style="color:#999999">]</span> actualTypeArguments <span style="color:#6272a4">=</span> paramType<span style="color:#999999">.</span><span style="color:#8be9fd">getActualTypeArguments</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
<span style="color:#6272a4">//        System.out.println(actualTypeArguments[0].getTypeName());</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#999999">(</span><span style="color:#999999">(</span>Class<span style="color:#999999">)</span>actualTypeArguments<span style="color:#999999">[</span><span style="color:#f1fa8c">0</span><span style="color:#999999">]</span><span style="color:#999999">)</span><span style="color:#999999">.</span><span style="color:#8be9fd">getName</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>
<span style="color:#6272a4">/*
    获取运行时类实现的接口
     */</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test5</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>

        Class<span style="color:#999999">[</span><span style="color:#999999">]</span> interfaces <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getInterfaces</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#ff79c6">for</span><span style="color:#999999">(</span>Class c <span style="color:#6272a4">:</span> interfaces<span style="color:#999999">)</span><span style="color:#999999">{</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>c<span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#999999">}</span>

        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#6272a4">//获取运行时类的父类实现的接口</span>
        Class<span style="color:#999999">[</span><span style="color:#999999">]</span> interfaces1 <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getSuperclass</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">.</span><span style="color:#8be9fd">getInterfaces</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#ff79c6">for</span><span style="color:#999999">(</span>Class c <span style="color:#6272a4">:</span> interfaces1<span style="color:#999999">)</span><span style="color:#999999">{</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>c<span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#999999">}</span>

    <span style="color:#999999">}</span>
    <span style="color:#6272a4">/*
        获取运行时类所在的包

     */</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test6</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>

        Package pack <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getPackage</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>pack<span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>

    <span style="color:#6272a4">/*
        获取运行时类声明的注解

     */</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">test7</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>

        Annotation<span style="color:#999999">[</span><span style="color:#999999">]</span> annotations <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getAnnotations</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#ff79c6">for</span><span style="color:#999999">(</span>Annotation annos <span style="color:#6272a4">:</span> annotations<span style="color:#999999">)</span><span style="color:#999999">{</span>
            System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>annos<span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#999999">}</span>
    <span style="color:#999999">}</span>

<span style="color:#999999">}</span>

</code></span></span></span>

六、调用运行时类的指定结构

关于setAccessible方法的使用

1. 调用运行时类中指定的属性

方法作用
public Field getField(String name)返回此Class对象表示的类或接口的指定的public的Field
public Field getDeclaredField(String name)返回此Class对象表示的类或接口的指定的Field

在Field中：

方法作用
public Object get(Object obj)取得指定对象obj上此Field的属性内容
public void set(Object obj,Object value)设置指定对象obj上此Field的属性内容

代码演示：

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java"><span style="color:#ff79c6">public</span> <span style="color:#ff79c6">class</span> ReflectionTest <span style="color:#999999">{</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">testField</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#ff79c6">throws</span> Exception <span style="color:#999999">{</span>
        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">//创建运行时类的对象</span>
        Person p <span style="color:#6272a4">=</span> <span style="color:#999999">(</span>Person<span style="color:#999999">)</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">newInstance</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>


        <span style="color:#6272a4">//获取指定的属性：要求运行时类中属性声明为public</span>
        <span style="color:#6272a4">//通常不采用此方法</span>
        Field id <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getField</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"id"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">/*
        设置当前属性的值

        set():参数1：指明设置哪个对象的属性   参数2：将此属性值设置为多少
         */</span>

        id<span style="color:#999999">.</span><span style="color:#8be9fd">set</span><span style="color:#999999">(</span>p<span style="color:#999999">,</span><span style="color:#f1fa8c">1001</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">/*
        获取当前属性的值
        get():参数1：获取哪个对象的当前属性值
         */</span>
        <span style="color:#ff79c6">int</span> pId <span style="color:#6272a4">=</span> <span style="color:#999999">(</span><span style="color:#ff79c6">int</span><span style="color:#999999">)</span> id<span style="color:#999999">.</span><span style="color:#8be9fd">get</span><span style="color:#999999">(</span>p<span style="color:#999999">)</span><span style="color:#999999">;</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>pId<span style="color:#999999">)</span><span style="color:#999999">;</span>


    <span style="color:#999999">}</span>
    <span style="color:#6272a4">/*
    如何操作运行时类中的指定的属性 -- 需要掌握
     */</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">testField1</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#ff79c6">throws</span> Exception <span style="color:#999999">{</span>
        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">//创建运行时类的对象</span>
        Person p <span style="color:#6272a4">=</span> <span style="color:#999999">(</span>Person<span style="color:#999999">)</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">newInstance</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">//1. getDeclaredField(String fieldName):获取运行时类中指定变量名的属性</span>
        Field name <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getDeclaredField</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"name"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">//2.保证当前属性是可访问的</span>
        name<span style="color:#999999">.</span><span style="color:#8be9fd">setAccessible</span><span style="color:#999999">(</span><span style="color:#8be9fd">true</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#6272a4">//3.获取、设置指定对象的此属性值</span>
        name<span style="color:#999999">.</span><span style="color:#8be9fd">set</span><span style="color:#999999">(</span>p<span style="color:#999999">,</span><span style="color:#f1fa8c">"Tom"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>name<span style="color:#999999">.</span><span style="color:#8be9fd">get</span><span style="color:#999999">(</span>p<span style="color:#999999">)</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>

</code></span></span></span>

2. 调用运行时类中的指定的方法

在这里插入图片描述

代码演示：

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java"> <span style="color:#6272a4">/*
    如何操作运行时类中的指定的方法 -- 需要掌握
     */</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">testMethod</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#ff79c6">throws</span> Exception <span style="color:#999999">{</span>

        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">//创建运行时类的对象</span>
        Person p <span style="color:#6272a4">=</span> <span style="color:#999999">(</span>Person<span style="color:#999999">)</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">newInstance</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">/*
        1.获取指定的某个方法
        getDeclaredMethod():参数1 ：指明获取的方法的名称  参数2：指明获取的方法的形参列表
         */</span>
        Method show <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getDeclaredMethod</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"show"</span><span style="color:#999999">,</span> String<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#6272a4">//2.保证当前方法是可访问的</span>
        show<span style="color:#999999">.</span><span style="color:#8be9fd">setAccessible</span><span style="color:#999999">(</span><span style="color:#8be9fd">true</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">/*
        3. 调用方法的invoke():参数1：方法的调用者  参数2：给方法形参赋值的实参
        invoke()的返回值即为对应类中调用的方法的返回值。
         */</span>
        Object returnValue <span style="color:#6272a4">=</span> show<span style="color:#999999">.</span><span style="color:#8be9fd">invoke</span><span style="color:#999999">(</span>p<span style="color:#999999">,</span><span style="color:#f1fa8c">"CHN"</span><span style="color:#999999">)</span><span style="color:#999999">;</span> <span style="color:#6272a4">//String nation = p.show("CHN");</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>returnValue<span style="color:#999999">)</span><span style="color:#999999">;</span>

        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"*************如何调用静态方法*****************"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">// private static void showDesc()</span>

        Method showDesc <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getDeclaredMethod</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"showDesc"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        showDesc<span style="color:#999999">.</span><span style="color:#8be9fd">setAccessible</span><span style="color:#999999">(</span><span style="color:#8be9fd">true</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        <span style="color:#6272a4">//如果调用的运行时类中的方法没有返回值，则此invoke()返回null</span>
<span style="color:#6272a4">//        Object returnVal = showDesc.invoke(null);</span>
        Object returnVal <span style="color:#6272a4">=</span> showDesc<span style="color:#999999">.</span><span style="color:#8be9fd">invoke</span><span style="color:#999999">(</span>Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>returnVal<span style="color:#999999">)</span><span style="color:#999999">;</span><span style="color:#6272a4">//null</span>

    <span style="color:#999999">}</span>


</code></span></span></span>

3. 调用运行时类中的指定的构造器

代码演示：

<span style="color:#000000"><span style="background-color:#282a36"><span style="color:pink"><code class="language-java">  <span style="color:#6272a4">/*
    如何调用运行时类中的指定的构造器
     */</span>
    <span style="color:#999999">@Test</span>
    <span style="color:#ff79c6">public</span> <span style="color:#ff79c6">void</span> <span style="color:#8be9fd">testConstructor</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#ff79c6">throws</span> Exception <span style="color:#999999">{</span>
        Class clazz <span style="color:#6272a4">=</span> Person<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">//private Person(String name)</span>
        <span style="color:#6272a4">/*
        1.获取指定的构造器
        getDeclaredConstructor():参数：指明构造器的参数列表
         */</span>

        Constructor constructor <span style="color:#6272a4">=</span> clazz<span style="color:#999999">.</span><span style="color:#8be9fd">getDeclaredConstructor</span><span style="color:#999999">(</span>String<span style="color:#999999">.</span><span style="color:#ff79c6">class</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">//2.保证此构造器是可访问的</span>
        constructor<span style="color:#999999">.</span><span style="color:#8be9fd">setAccessible</span><span style="color:#999999">(</span><span style="color:#8be9fd">true</span><span style="color:#999999">)</span><span style="color:#999999">;</span>

        <span style="color:#6272a4">//3.调用此构造器创建运行时类的对象</span>
        Person per <span style="color:#6272a4">=</span> <span style="color:#999999">(</span>Person<span style="color:#999999">)</span> constructor<span style="color:#999999">.</span><span style="color:#8be9fd">newInstance</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"Tom"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#8be9fd">println</span><span style="color:#999999">(</span>per<span style="color:#999999">)</span><span style="color:#999999">;</span>

    <span style="color:#999999">}</span>

<span style="color:#999999">}</span>

</code></span></span></span>
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