Spring统一异常处理

1、为什么要用Spring的统一异常处理？

　　项目中无论是controller层、service层还是dao层都会有异常发生。每个过程都单独处理异常，系统的代码耦合度高，工作量大且不好统一，维护的工作量也很大。所以将异常处理从各处理过程解耦出来，这样既保证了相关处理过程的功能较单一，也实现了异常信息的统一处理和维护

2、Spring统一异常处理的方式有哪些？

　　2.1 使用Spring MVC提供的简单异常处理器SimpleMappingExceptionResolver。

　　2.2 实现Spring的异常处理接口HandlerExceptionResolver 自定义自己的异常处理器。

　　2.3 使用@ExceptionHandler注解实现异常处理

3、做实验

　　3.1使用SimpleMappingExceptionResolver

　　　　3.1.1 在spring的配置文件applicationContext.xml文件中配置SimpleMappingExceptionResolver

<!-- springmvc提供的简单异常处理器 -->

    <bean

        class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">

        <!-- 定义默认的异常处理页面，这里的error表示的是error.jsp页面-->

        <property name="defaultErrorView" value="error" />

        <!-- 定义异常处理页面用来获取异常信息的变量名，也可不定义，默认名为exception-->

        <property name="exceptionAttribute" value="ex" />

        <!-- 定义需要特殊处理的异常，这是重要点 -->

        <property name="exceptionMappings">

            <props>

                <!-- 这里的exception表示的是exception.jsp页面 -->

                <prop key="org.hope.lee.exception.UserException">exception</prop>

                <prop key="org.hope.lee.exception.CustomerException">customerException</prop>

            </props>

            <!-- 还可以定义其他的自定义异常 -->

        </property>

    </bean>

　　　　3.1.2定义自己的异常

package org.hope.lee.exception;

public class UserException extends Exception{

    private static final long serialVersionUID = 1L;

    private String errorMsg;

    public UserException(String errorMsg) {

        super();

        this.errorMsg = errorMsg;

    }

    public String getErrorMsg() {

        return errorMsg;

    }

    public void setErrorMsg(String errorMsg) {

        this.errorMsg = errorMsg;

    }

}

package org.hope.lee.exception;

public class CustomerException extends RuntimeException{

    private String errorException;

    public CustomerException(String errorException) {

        super();

        this.errorException = errorException;

    }

    public String getErrorException() {

        return errorException;

    }

    public void setErrorException(String errorException) {

        this.errorException = errorException;

    }

}

　　　　3.1.3 写几个简单的页面error.jsp exception.jsp customerException.jsp

error.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

</head>

<body>

    sorry, your request has some errors

</body>

</html>

exception.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

</head>

<body>

    sorry, your request has ${ex.errorMsg}

</body>

</htm

customerException.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

</head>

<body>

    sorry, your request has customerException:${ex.errorException}

</body>

</html>

　　　　3.1.4 Controller层

package org.hope.lee.controller;

import org.hope.lee.exception.CustomerException;

import org.hope.lee.exception.UserException;

import org.hope.lee.model.User;

import org.hope.lee.service.UserService;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Controller;

import org.springframework.ui.ModelMap;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.servlet.ModelAndView;

@Controller

@RequestMapping("/user")

public class UserController {

    @Autowired

    private UserService userService;

    @RequestMapping("/index")

    public String index() {

        return "userDetail";

    }

    @RequestMapping("/detail")

    public ModelAndView detail(String id) throws UserException {

        if("0".equals(id)) {

            throw new UserException("id不能为0");

        }

        if("10".equals(id)) {

            throw new CustomerException("id不能为10");

        }

        User user = userService.findUserById(Integer.parseInt(id));

        ModelAndView mv = new ModelAndView();

        mv.addObject("user", user);

        mv.setViewName("success");

        return mv;

    }

}

　　　　3.1.4 进行测试

　　　　①启动项目

　　　　②浏览器输入：http://localhost:8088/springmvc-exception/user/detail?id=1(这个是正常时候)

　　　　③浏览器输入：http://localhost:8088/springmvc-exception/user/detail?id=0

　　　　④浏览器输入：http://localhost:8088/springmvc-exception/user/detail?id=10

　　3.2自定义全局异常处理。

　　　　3.2.1 定义自己的异常处理类实现HandlerExceptionResolver

package org.hope.lee.exception;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.HandlerExceptionResolver;

import org.springframework.web.servlet.ModelAndView;

/**

 * 定义全局异常处理器

 */

public class ExceptionResolver implements HandlerExceptionResolver{

    @Override

    public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler,

            Exception ex) {

        ModelAndView mav = new ModelAndView();

        if(ex instanceof UserException) {

            UserException ue = (UserException)ex;

            mav.addObject("ex", ue);

            mav.setViewName("exception");

        } else if(ex instanceof CustomerException) {

            CustomerException ce = (CustomerException)ex;

            mav.addObject("ex", ce);

            mav.setViewName("customerException");

        } else {

            mav.addObject("ex", "未知错误");

            mav.setViewName("error");

        }

        return mav;

    }

}

　　　　3.2.2 在applicationContext.xml中配置异常处理器

<bean class="org.hope.lee.exception.ExceptionResolver"/>

　　3.3 使用@ExceptionHandler

　　　　3.3.1 定义一个BaseController，所有的Controller层都要继承它

package org.hope.lee.controller;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.hope.lee.exception.CustomerException;

import org.hope.lee.exception.UserException;

import org.springframework.web.bind.annotation.ExceptionHandler;

public class BaseController {

    @ExceptionHandler

    public String exp(HttpServletRequest req, HttpServletResponse resp, Exception ex) {

        req.setAttribute("ex", ex);

        if(ex instanceof UserException) {

            return "exception";

        } else if(ex instanceof CustomerException) {

            return "customerException";

        } else {

            return "error";

        }

    }

}

　　　　3.3.2 定义一个Controller，继承BaseController

package org.hope.lee.controller;

import org.hope.lee.service.SellerService;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

@Controller

public class SellerController extends BaseController{

    @Autowired

    private SellerService sellerService;

    @RequestMapping("/good/update")

    public void updateGood(String id) {

        sellerService.updateGoodsById(Integer.parseInt(id));

    }

}

　　　　3.3.3 测试一下，启动项目在浏览器访问：http://localhost:8088/springmvc-exception/good/update?id=0

https://gitee.com/huayicompany/spring-learn/tree/master/springmvc-exception

参考：

[1] 博客，http://blog.csdn.net/eson_15/article/details/51731567

[2] 博客，http://luanxiyuan.iteye.com/blog/2354081