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SpringMVC异常处理机制

独西楼Q 2022-05-06 阅读 38
springjavamaven

SpringMVC异常处理机制

  1. 创建spring-exception项目工程【web项目】

    1. 在pox.xml配置文件中导入需要的依赖坐标和tomcat7插件

      <?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>spring_exception</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.32</version>
        </dependency>
        <dependency>
            <groupId>c3p0</groupId>
            <artifactId>c3p0</artifactId>
            <version>0.9.1.2</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.10</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.0.5.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>5.0.5.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>5.0.5.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.0.5.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.0.1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>javax.servlet.jsp-api</artifactId>
            <version>2.2.1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.9.0</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.9.0</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-annotations</artifactId>
            <version>2.9.0</version>
        </dependency>
        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.3.1</version>
        </dependency>
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.3</version>
        </dependency>
        <dependency>
            <groupId>commons-logging</groupId>
            <artifactId>commons-logging</artifactId>
            <version>1.2</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.7.7</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>5.0.5.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>5.0.5.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>jstl</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.tomcat.maven</groupId>
                <artifactId>tomcat7-maven-plugin</artifactId>
                <version>2.2</version>
            </plugin>
        </plugins>
    </build>
</project>

    2. 在main包下创建com.zcl.controller包，并在包下创建DemoController类

      package com.zcl.controller;

import com.zcl.exception.MyException;
import com.zcl.service.DemoService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import java.io.FileNotFoundException;

@Controller
public class DemoController {

    @Autowired
    private DemoService demoService;

    @RequestMapping(value = "/show")
    public String show() throws FileNotFoundException, MyException {
        System.out.println("show running......");
        //demoService.show1();
        //demoService.show2();
        //demoService.show3();
        //demoService.show4();
        demoService.show5();
        return "index";
    }

}

    3. 在main包下创建com.zcl.service包，并在包下创建DemoService接口

      package com.zcl.service;

import com.zcl.exception.MyException;

import java.io.FileNotFoundException;

public interface DemoService {
    void show1();

    void show2();

    void show3() throws FileNotFoundException;

    void show4();

    void show5() throws MyException;
}


      package com.zcl.service;

import com.zcl.exception.MyException;
import org.springframework.web.servlet.view.InternalResourceViewResolver;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;

public class DemoServiceImpl implements DemoService {
    @Override
    public void show1() {
        System.out.println("抛出类型转换异常....");
        Object str = "zhangsan";
        Integer num = (Integer)str;
    }

    @Override
    public void show2() {
        System.out.println("抛出除零异常....");
        int i = 1/0;
    }

    @Override
    public void show3() throws FileNotFoundException {
        System.out.println("文件找不到异常....");
        InputStream in = new FileInputStream("C:/xxx/xxx/xxx.txt");
    }

    @Override
    public void show4() {
        System.out.println("空指针异常.....");
        String str = null;
        str.length();
    }

    @Override
    public void show5() throws MyException {
        System.out.println("自定义异常....");
        throw new MyException();
    }
}

    4. 在main包下创建com.zcl.exception包，并在包下创建MyException自定义异常类

      package com.zcl.exception;

public class MyException extends Exception {

}

    5. 在resources包下创建applicationContext.xml配置文件

      <?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
       http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
">

    <bean id="demoService" class="com.zcl.service.DemoServiceImpl"></bean>


</beans>

    6. 在webapp.WEB-INF包下的web.xml配置文件

      <?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext.xml</param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <servlet>
        <servlet-name>DispatcherServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:spring-mvc.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>DispatcherServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

    7. 在resources包下创建spring-mvc.xml配置文件

      <?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
       http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
       http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
">

    <!--1、mvc注解驱动-->
    <mvc:annotation-driven/>

    <!--2、配置视图解析器-->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

    <!--3、静态资源权限开放-->
    <mvc:default-servlet-handler/>

    <!--4、组件扫描  扫描Controller-->
    <context:component-scan base-package="com.zcl.controller"/>



</beans>

  2. 异常处理的思路

    系统的Dao、Service、Controller出现都通过throws Exception向上抛出，最后由SpringMVC前端控制器交由异常处理器进行异常处理，如下图：

    [外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-GTINIu5M-1651755937696)(image/image-20220505194524025.png)]

  3. 异常处理的两种方式

    1. 使用Spring MVC提供的简单异常处理器SimpleMapping ExceptionResolver

      启动项目访问：http://localhost:8080/spring_exception/show 会出现页面报错提示

      [外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-pz7dA7EA-1651755937697)(image/image-20220505204250333.png)]

      <!--5、配置异常处理器-->
<bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
    <!--配置之后有异常信息就会跳转到value声明的页面-->
    <!--<property name="defaultErrorView" value="error"/> 默认错误视图-->
    <property name="exceptionMappings">
        <map>
            <!--key为异常的类型，value为对应异常的跳转路径-->
            <entry key="java.lang.ClassCastException" value="error"/>
            <entry key="java.lang.ClassCastException" value="error"/>
        </map>
    </property>
</bean>

    2. 实现Springl的异常处理接口HandlerExceptionResolver自定义自己的异常处理器

      1. 创建异常处理器类实现HandlerExceptionResolver

        在main包下创建com.zcl.resolver包并创建MyExceptionResolver类实现接口，并重新接口的方法，完成异常的判断

        package com.itheima.resolver;

import com.itheima.exception.MyException;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 项目名称：Spring
 * 描述：自定义异常处理器
 *
 * @author zhong
 * @date 2022-05-05 20:49
 */
public class MyExceptionResolver implements HandlerExceptionResolver {
    /**
     * 参数Exception：异常对象
     * 返回值ModelAndView：跳转到错误视图信息
     * @param httpServletRequest
     * @param httpServletResponse
     * @param o
     * @param e
     * @return
     */
    @Override
    public ModelAndView resolveException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) {
        ModelAndView modelAndView = new ModelAndView();
        // 根据参数e来判断异常
        if(e instanceof MyException){
            modelAndView.addObject("info","自定义异常");
        }else if(e instanceof ClassCastException){
            modelAndView.addObject("info","类转换异常");
        }
        // 设置异常的跳转视图
        modelAndView.setViewName("error");
        return modelAndView;
    }
}

      2. 配置异常处理器

        <!--自定义异常配置，如果之前有配置spring-mvc的异常配置需要注释掉-->
<bean class="com.itheima.resolver.MyExceptionResolver"/>

      3. 编写异常页面

      4. 测试异常跳转

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