Java SpringMVC異常處理機制詳解

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("類型轉換異常");
        Object str = "zhangsan";
        Integer num = (Integer) str;
    }
    public void show2() {
        System.out.println("拋出除零異常");
        int i = 1 / 0;
    }
    public void show3() throws FileNotFoundException {
        System.out.println("文件找不到異常");
        InputStream in = new FileInputStream("C:/xxx/xxx/xxx.txt");
    }
    public void show4() {
        System.out.println("空指針異常");
        String str = null;
        str.length();
    }
    public void show5() throws MyException {
        System.out.println("自定義異常");
        throw new MyException();
    }
}

<!--配置異常處理器-->
    <bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
        <!--如果下面全都對不上，就會采用這個默認的defaultErrorView所對應的value值的視圖-->
        <property name="defaultErrorView" value="error"></property>
        <property name="exceptionMappings">
            <map>
                <!--類型轉換異常，拋瞭什麼異常，就會跳轉到value值對應的字符串顯示的頁面-->
                <entry key="java.lang.ClassCastException" value="error"></entry>
                <!--自定義異常-->
                <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 {
    /*這是HandlerExceptionResolver中必須要實現的方法
      參數Exception：異常對象
      返回值ModelAndView：跳轉到錯誤視圖信息
     */
    public ModelAndView resolveException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) {
        ModelAndView md = new ModelAndView();
        /*
        這裡隻是大致做一個代碼邏輯的演示
        實際開發當中並不會這樣寫，沒什麼意義
        下面的演示隻是可以告訴我們可以在這個方法裡面進行異常信息的判斷
         */
        if(e instanceof MyException){
            md.addObject("info","自定義異常");
        }else if(e instanceof ClassCastException){
            md.addObject("info","類型轉換異常");
        }
        md.setViewName("error");
        return md;
    }
}

 <!--自定義異常處理器-->
    <bean class="com.itheima.resolver.MyExceptionResolver"></bean>