Java SpringMVC异常处理机制详解

package com.itheima.controller;
import com.itheima.exception.MyException;
import com.itheima.service.DemoService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
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";
    }
}

package com.itheima.service;
import com.itheima.exception.MyException;
import java.io.FileNotFoundException;
public interface DemoService {
    public void show1();
    public void show2();
    public void show3() throws FileNotFoundException;
    public void show4();
    public void show5() throws MyException;
}

package com.itheima.service.impl;
import com.itheima.exception.MyException;
import com.itheima.service.DemoService;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
public class DemoServiceImpl implements DemoService {
    public void show1() {
        System.out.println("类型转换异常");
        Object str = "zhangsan";
        Integer num = (Integer) str;
    }
    public void show2() {
        System.out.println("抛出除零异常");
        int i = 1 / 0;
    }
    public void show3() throws FileNotFoundException {
        System.out.println("文件找不到异常");
        InputStream in = new FileInputStream("C:/xxx/xxx/xxx.txt");
    }
    public void show4() {
        System.out.println("空指针异常");
        String str = null;
        str.length();
    }
    public void show5() throws MyException {
        System.out.println("自定义异常");
        throw new MyException();
    }
}

<!--配置异常处理器-->
    <bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
        <!--如果下面全都对不上，就会采用这个默认的defaultErrorView所对应的value值的视图-->
        <property name="defaultErrorView" value="error"></property>
        <property name="exceptionMappings">
            <map>
                <!--类型转换异常，抛了什么异常，就会跳转到value值对应的字符串显示的页面-->
                <entry key="java.lang.ClassCastException" value="error"></entry>
                <!--自定义异常-->
                <entry key="com.itheima.exception.MyException" value="error"></entry>
            </map>
        </property>
    </bean>

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;
public class MyExceptionResolver implements HandlerExceptionResolver {
    /*这是HandlerExceptionResolver中必须要实现的方法
      参数Exception：异常对象
      返回值ModelAndView：跳转到错误视图信息
     */
    public ModelAndView resolveException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) {
        ModelAndView md = new ModelAndView();
        /*
        这里只是大致做一个代码逻辑的演示
        实际开发当中并不会这样写，没什么意义
        下面的演示只是可以告诉我们可以在这个方法里面进行异常信息的判断
         */
        if(e instanceof MyException){
            md.addObject("info","自定义异常");
        }else if(e instanceof ClassCastException){
            md.addObject("info","类型转换异常");
        }
        md.setViewName("error");
        return md;
    }
}

 <!--自定义异常处理器-->
    <bean class="com.itheima.resolver.MyExceptionResolver"></bean>