04.SpringMVC中的异常处理

1.结构图

04.SpringMVC中的异常处理

2.控制类UserController：

package cn.itcast.controller;

import cn.itcast.exception.SysException;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
@RequestMapping("/user")
public class UserController {
    @RequestMapping("/testException")
    public String testException() throws SysException{
        System.out.println("testException异常执行了.....");
        try {
            //模拟异常
            int i = 1/0;
        } catch (Exception e) {
            //打印异常信息
            e.printStackTrace();
            //抛出自定义异常信息
            throw new SysException("查询所有出错...");
        }
        return "success";
    }
}

3.存储异常信息SysException

package cn.itcast.exception;


/*自定义异常类*/
public class SysException extends Exception {

    //存储异常信息
    private String message;

    @Override
    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
    /*构造方法*/
    public SysException(String message) {
        this.message = message;
    }
}

4.SysExceptionResolver处理异常(拿到异常并且处理异常)：

package cn.itcast.exception;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/*自定义异常处理器*/
public class SysExceptionResolver implements HandlerExceptionResolver {
    /*
    * 当处理业务时有异常 SysException中的异常被捕获的时候，
    * 那么这个异常就会被抛到这个SysExceptionResolver自定义异常处理器中来
    * 让我们进行处理
    */
    /*
    * ModelAndView 处理异常逻辑
    */
    public ModelAndView resolveException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception ex) {
        //获取到异常对象
        SysException e = null;
        if (e instanceof SysException) {
            e = (SysException)ex;
        }else {
            e = new SysException("系统维护中...........");
            //然后让美工写一个好的维护界面
        }
        //创建ModelAndView对象
        ModelAndView mv = new ModelAndView();
        //通过对象获取信息e.getMessage()
        mv.addObject("errorMsg",e.getMessage());
        mv.setViewName("error");
        return mv;
    }
}

5.error.jsp(有错误异常跳这个页面)

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    ${errorMsg}
</body>
</html>

6.success.jsp(成功之后跳转)

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <h>恭喜！！！跳转成功，哦吼</h>
</body>
</html>

7.index.jsp(首页.jsp)

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <h3>异常处理</h3>
    <a href="user/testException">点击</a>
</body>
</html>

8.web.xml

<!--<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >-->
<web-app>
  <display-name>Archetype Created Web Application</display-name>

  <display-name>Archetype Created Web Application</display-name>
  <!--01.前端控制器servlet-->
  <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:springmvc.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <!--02.映射：/表示在什么路径下都可以-->
  <!--可以被请求到-->
  <servlet-mapping>
    <!--05.映射到这里来使用-->
    <servlet-name>dispatcherServlet</servlet-name>
    <!--03.你拦截的路径，发任何请求都会经过这个拦截到-->
    <url-pattern>/</url-pattern>
  </servlet-mapping>

  <!--过滤器:解决中文乱码的过滤器-->
  <filter>
    <filter-name>characterEncodingFilter</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
      <param-name>encoding</param-name>
      <param-value>UTF-8</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>characterEncodingFilter</filter-name>
    <!--映射过来的拦截路径-->
    <url-pattern>/*</url-pattern>
  </filter-mapping>
</web-app>

<properties>
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  <maven.compiler.source>1.8</maven.compiler.source>
  <maven.compiler.target>1.8</maven.compiler.target>
  <!--版本锁定：为了解决版本统一改的问题-->
  <spring.version>5.0.2.RELEASE</spring.version>
</properties>

<dependencies>
  <dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>${spring.version}</version>
  </dependency>

  <dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-web</artifactId>
    <version>${spring.version}</version>
  </dependency>

  <dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-webmvc</artifactId>
    <version>${spring.version}</version>
  </dependency>

  <dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>servlet-api</artifactId>
    <version>2.5</version>
    <scope>provided</scope>
  </dependency>

  <dependency>
    <groupId>javax.servlet.jsp</groupId>
    <artifactId>jsp-api</artifactId>
    <version>2.0</version>
    <scope>provided</scope>
  </dependency>
</dependencies>

10.总结：当我们的程序出现错误的时候，总是会显示在网页页面上，所以这一种开发是不好的，因此捕获该异常，然后让前端写一个好看的页面，错误出现在后台即可。