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 {
    
    public ModelAndView resolveException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) {
        ModelAndView md = new ModelAndView();
        
        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>