Java反射机制概述
- 前言
- 一、Java反射机制概述
- 1. Java Reflection
- 2. 动态语言 vs 静态语言
- 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
- 1.3 了解:什么时候会发生类初始化?
- 1.4 类加载器的作用
- 1.5 JVM中不同类型的类的加载器
- 1.6 代码演示
- 2. 何为Class类?
- 3. Class类的常用方法方法
- 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
- 四、 创建运行时类的对象
- 1. 引入
- 2. 语法步骤
- 3. 代码演示
- 4. 体会反射的动态性
- 五、获取运行时类的完整结构
- 1. 获取当前运行时类的属性结构
- 2. 获取当前运行时类的方法结构
- 3. 获取当前运行时类的构造器结构
- 六、调用运行时类的指定结构
- 1. 调用运行时类中指定的属性
- 2. 调用运行时类中的指定的方法
- 3. 调用运行时类中的指定的构造器
前言
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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
<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
1.5 JVM中不同类型的类的加载器
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>
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
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>