前言

在基于Servlet-JSP技术开发的项目中，异常的显示是和前后端分离项目不同的。项目业务层所报出的异常会影响浏览器的页面展示，出现404，500，等常见的浏览器提供的报错页面。这样的话十分影响用户体验。springmvc支持自定义全局异常处理，可以自定义异常处理页面，增强用户体验。

1、导入依赖

 <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>5.3.24</version>
    </dependency>

    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>4.0.1</version>
    </dependency>

    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <version>1.18.24</version>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.13.3</version>
    </dependency>
    <dependency>
      <groupId>jstl</groupId>
      <artifactId>jstl</artifactId>
      <version>1.2</version>
    </dependency>

2、配置springmvc.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd"> <!-- bean definitions here -->

    <!-- springmvc三大组件 -->
    <mvc:annotation-driven/>

    <!-- 放行静态资源：html，css，js... -->
    <mvc:default-servlet-handler/>

    <!-- 扫描对应包下的注解 -->
    <context:component-scan base-package="com.wmj"/>

    <!--        &lt;!&ndash; 视图解析器，根据需求配置 &ndash;&gt;-->
            <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
                    <!-- 配置前缀 -->
                    <property name="prefix" value="/WEB-INF/jsp"></property>
                    <!-- 配置后缀 -->
                    <property name="suffix" value=".jsp"></property>
            </bean>

</beans>

3、配置web.xml文件

<!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>
  <!-- 配置前端控制器 -->
  <servlet>
    <servlet-name>dispatcherServlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>

    <!-- 加载springmvc配置文件 -->
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>classpath:springmvc.xml</param-value>
    </init-param>
  </servlet>

  <servlet-mapping>
    <servlet-name>dispatcherServlet</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>
</web-app>

4、编写异常处理组件

package com.wmj.handler;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * --效率，是成功的核心关键--
 *
 * @Author lzl
 * @Date 2023/2/16 09:46
 */
@Configuration
public class MyExceptionHandler implements HandlerExceptionResolver {
    @Override
    public ModelAndView resolveException(HttpServletRequest request,
                                         HttpServletResponse response,
                                         Object handler,
                                         Exception ex) {
        System.out.println("执行异常处理类");
        ModelAndView view = new ModelAndView();
        if(ex instanceof NullPointerException){
            view.addObject("msg","空指针异常");
        }else if(ex instanceof ArrayIndexOutOfBoundsException){
            view.addObject("msg","数组下标越界异常");
        }else if(ex instanceof ArithmeticException){
            view.addObject("msg","算数异常");
        }else{
            view.addObject("msg",ex.getMessage());
        }
        view.setViewName("/error");
        return view;
    }
}

5、编写测试controller

package com.wmj.controller;

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


/**
 * --效率，是成功的核心关键--
 *
 * @Author lzl
 * @Date 2023/2/16 09:59
 */
@Controller
@RequestMapping("/exception")
public class ExceptionController {
    @RequestMapping("/test")
    public String testException(){
        int[] arr = new int[3];
        arr[0] = 1;
        arr[1] = 1;
        arr[2] = 1;
        arr[3] = 2;
        //此时下标越界
        return "success";
    }
}

6、准备异常处理页面

默认访问首页跳转测试controller

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<body>
<h2>Hello World!</h2>
<a href="http://localhost:8080/exception/test">点一下跳转</a>
</body>
</html>

异常处理页打印信息

<%--
  Created by IntelliJ IDEA.
  User: 我是谁
  Date: 2023/2/16
  Time: 09:56
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
${msg}
</body>
</html>

7、测试

成功