springmvc异常处理

骑猪看日落 2022-05-25 01:43 252阅读 0赞

1.通过@ExceptionHandler注释处理异常：

1）Handler--->()

package com.majun.springmvc.test;
    
    import java.io.IOException;
    
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestParam;
    import org.springframework.web.multipart.MultipartFile;
    
    @Controller
    @RequestMapping("/spring")
    public class Test {
    	
    	@RequestMapping("/testHandlerExceptionResolver")
    	public String testHandlerExceptionResolver(@RequestParam("i") int i) {//获取页面请求参数，写入到方法当中
    		System.out.println("result="+ 10/i);
    		return "success";//返回一个提示没有错误的页面
    	}}

2)index.jsp 页面：

<%@ 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>
    
    <a href="spring/testHandlerExceptionResolver?i=2">Test HandlerExceptionResolver</a>
    <hr>
    </body>
    </html>

3）springmvc.xml配置文件

<?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/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
    		http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd">
    			
    		<context:component-scan base-package="com.majun.springmvc"></context:component-scan>
    		
    		<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    		<property name="prefix" value="/WEB-INF/views/"></property>
    		<property name="suffix" value=".jsp"></property>
    		
    		</bean>
    </beans>

4)处理异常的包：

package com.majun.springmvc.Exception;
    
    import org.springframework.web.bind.annotation.ControllerAdvice;
    import org.springframework.web.servlet.ModelAndView;
    
    @ControllerAdvice
    public class ExceptionHandler {
    	
    //	1.在@ExceptionHandler 方法的入参中可以加入Exception类型的参数，该参数对应异常对象
    //	2.@ExceptionHandler 方法的入参中不能传入Map ，若希望将异常信息传到error页面，则需要使用ModelAndView 作为返回值
    //	3.@ExceptionHandler 方法标记的异常有优先级问题
    //	4.@ControllerAdvice ：如当前Handler 中找不到 @ExceptionHandler 方法标记的异常，则将去@ControllerAdvice 标记的类中
    //	查找@ExceptionHandler 标记的方法去处理异常
    	
    	@org.springframework.web.bind.annotation.ExceptionHandler({ArithmeticException.class})
    	public ModelAndView testArithmeticException(Exception er) {
    		System.out.println("出异常了"+er);
    		ModelAndView mc=new ModelAndView("error");//error视图名viewname
    		mc.addObject("exception",er);//在错误页面增加错误信息,使用${exception}
    		return mc;//转到错误页面
    	}
    
    }

5）显示错误信息页面：

<%@ 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>
    
        <h2>error page</h2>
       ${exception }
    </body>
    </html>

![20180505194621498][]

6）web.xml

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    	xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
    	version="3.1">
    	<display-name>springmvc_2</display-name>
    	<welcome-file-list>
    		<welcome-file>index.jsp</welcome-file>
    	</welcome-file-list>
    	
    	<servlet>
    		<servlet-name>springDispatcherServlet</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>
    
    	
    	<servlet-mapping>
    		<servlet-name>springDispatcherServlet</servlet-name>
    		<url-pattern>/</url-pattern>
    	</servlet-mapping>
    	
    	
          <filter>
              <filter-name>HiddenHttpMethodFilter</filter-name>
              <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
          </filter>
          
          <filter-mapping>
              <filter-name>HiddenHttpMethodFilter</filter-name>
              <url-pattern>/*</url-pattern>
          </filter-mapping>
    	
    
    </web-app>

### 1. 文件上传 ###

*  Spring 使用 Jakarta Commons FileUpload 技术实现了一个 MultipartResolver 实现类:  
    `CommonsMultipartResolver`;
 *  SpringMVC 上下文中默认没有装配 MultipartResolver,因此默认情况下不能处理文件的上传;  
    若要使用上传功能,需要在上下文中配置 `MultipartResolver`;

// 1. 导入 jar 包
          /* commons-fileupload;
           * commons-io;
           */
    
    // 2. 配置 MultipartResolver(多媒体解析器)
    <bean id="multipartResolver"
            class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <property name="defaultEncoding" value="UTF-8"></property>
    
        
        <property name="maxUploadSize" value="1048576"/>
    </bean>
    
    // index.jsp
    <h2>文件上传</h2>
    <form action="${pageContext.request.contextPath}/testUpload" method="post"
                                                        enctype="multipart/form-data">
        file1:<input type="file" name="upload"/><br/>
        file2:<input type="file" name="upload"/><br/>
        file3:<input type="file" name="upload"/><br/>
        <input type="submit" value="上传"/><br/>
    </form>
    
    
    // Demo.java
    @RequestMapping(value="/testUpload",method=RequestMethod.POST)
    public String testUpload(@RequestParam("upload") MultipartFile[] file)
                                         throws IllegalStateException, IOException {
    
        for(MultipartFile mf : file){
            if(!mf.isEmpty()){
                mf.transferTo(new File("/Users/用户名/Documents/上传/"+
                                                              mf.getOriginalFilename()));
            }
        }
        return "ok";
    }

### 2. 自定义拦截器 ###

1.  自定义的拦截器必须实现 HandlerInterceptor 接口:
    
     *  `preHandle()`:这个方法在业务处理器处理请求之前被调用,在该方法中对用户请求 request 进行  
        处理;如果拦截处理后,还需要调用其他的拦截器,或者是业务处理器,则返回 true; 否则,返回false;
     *  `postHandle()`:这个方法在业务处理器处理完请求后,但是,DispatcherServlet 向客户端返回  
        响应前被调用,处理用户的 request请求;
     *  `afterCompletion()`:这个方法在 DispatcherServlet 完全处理完请求后被调用,可以在该方  
        法中进行一些资源清理的操作;

// FirstInterceptor.java
    public class FirstInterceptor implements HandlerInterceptor{
        public boolean preHandle(HttpServletRequest req,HttpServletResponse resp,
                                                    Object handler)throws Exception{
            System.out.println("FirstInterceptor.....preHandle");
            return true;                                                    
        }
    
        public void postHandle(HttpServletRequest req, HttpServletResponse resp,
                        Object handler, ModelAndView modelAndView)throws Exception{
            System.out.println("FirstInterceptor.....postHandle");         
        }
    
        public void afterCompletion(HttpServletRequest req,HttpServletResponse resp,
                                      Object handler,Exception ex) throws Exception{
            System.out.println("FirstInterceptor.....afterCompletion");                    
        }
    }
    
    // 注册该拦截器
    <mvc:interceptors>
        <bean id="firstInterceptor"
                            class="cn.itcast.springmvc.interceptor.firstInterceptor"/>
    </mvc:interceptors>
    
    // index.jsp
    示例:<a href="${pageContext.request.contextPath}/helloworld">点击这里</a>
    
    // Demo.java
    @Controller
    public class Demo{
        @RequestMapping(value="/hellowrold",method=RequestMethod.GET)
        public String helloworld(){
            System.out.println("======helloworld");
            return "ok";
        }
    }

##### 运行结果: #####

![1222878-20171104123209451-2127638057.png][]

#### 2.1 拦截器配置 ####

// 自定义两个拦截器
    // FirstInterceptor.java(同上)
    // SecondInterceptor.java
    public class SecondInterceptor implements HandlerInterceptor{
        public boolean preHandle(HttpServletRequest req,HttpServletResponse resp,
                                                    Object handler)throws Exception{
            System.out.println("SecondInterceptor.....preHandle");
            return true;                                                    
        }
    
        public void postHandle(HttpServletRequest req, HttpServletResponse resp,
                        Object handler, ModelAndView modelAndView)throws Exception{
            System.out.println("SecondInterceptor.....postHandle");         
        }
    
        public void afterCompletion(HttpServletRequest req,HttpServletResponse resp,
                                      Object handler,Exception ex) throws Exception{
            System.out.println("SecondInterceptor.....afterCompletion");                    
        }
    }
    
    // 注册拦截器
    <mvc:interceptors>
        <bean id="firstInterceptor"
                            class="cn.itcast.springmvc.interceptor.FirstInterceptor"/>
    
        <mvc:interceptor>
            <mvc:mapping path="/emps"></mvc:mapping>
            <bean id="secondInterceptor"
                            class="cn.itcast.springmvc.interceptor.SecondInterceptor"/>
        </mvc:interceptor>
    </mvc:interceptors>
    
    // Demo.java
    @Controller
    public class Demo{
        @RequestMapping(value="/emps",method=RequestMethod.GET)
        public String list(Map<String,Object> map){
    
            System.out.println("emps .... 执行");
            map.put("employees",employeeService.getAll());
            return "list";
        }
    }
    
    // index.jsp
    查询所有员工: <a href="${pageContext.request.contextPath}/emps">查询所有</a>

##### 结果分析 #####

*  第一个拦截器 `preHandler` 返回 true,第二个也为 true;

![1222878-20171104123230951-845925520.png][]

*  第一个拦截器返回 false,第二个为true或false;

![1222878-20171104123240873-1170080086.png][]

*  第一个拦截器返回 true,第二个为 false;

![1222878-20171104123259732-1490369580.png][]

### 3. 异常处理 ###

1.  SpringMVC 通过 `HandlerExceptionResolver`接口处理程序的异常,包括Handler映射,数据绑定以  
    及目标方法执行时,发生的异常;
2.  SpringMVC 提供的 `HandlerExceptionResolver`接口的实现类:
    
     *  `ExceptionHandlerExceptionResolver`;
     *  `DefaultHandlerExceptionResolver`;
     *  `ResponseStatusExdeptionResolver`;
     *  `SimpleMappingExceptionResolver`;

#### 3.1 HandlerExceptionResolver ####

*  `@ExceptionHandler`只处理当前 handler 方法中抛出的异常

// index.jsp
    异常示例:<a href="{pageContext.request.contextPath}/testHandler?age=5">异常处理1</a>
    
    // Demo.java
    @Controller
    public class Demo{
    
        @RequestMapping(value="/testHandler",method=RequestMethod.GET)
        public String testHandler(@RequestParam("age") Integer age){
            int result = 10 / age;
            System.out.println(result);
            return "ok";
        }
    
        // 如果请求参数 age=0, 会报异常
    
        // error.jsp
        <body>
        抱歉,系统繁忙,请稍候在试....
        </body>
    
        // 第一种方式: 返回到错误页面,不带异常信息
        @ExceptionHandler(value={ArithmeticException.class})
        public String dealHandlerExceptionResolver(Exception e){
    
            System.out.println("111111"+e.getMessage());
            return "error";
        }
    
        // 第二种方式: 将异常信息返回到错误页面, 需要使用 ModelAndView, 不能使用 Map
        @ExceptionHandler(value={ArithmeticException.class})
        public ModelAndView dealHandlerExceptionResolver(Excetption e){
    
            System.out.println("22222"+e.getMessage());
            ModelAndView mv = new ModelAndView();
            mv.addObject("myexception",e.getMessage());
            mv.setViewName("error");
            return mv;
        }
    
        // error.jsp
        <body>
        抱歉,系统繁忙,请稍候在试....<br/>
        异常信息:${requestScope.myexception}
        </body>
    
        // 异常优先级问题
        // ArithmeticExcetion 继承了 RuntimeException
        // 如果一个类中既有ArithmeticException, 也有 RuntimeException
        // 如果出现 ArithmeticException, 会执行ArithmeticException
        @ExceptionHandler(value={RuntimeException.class})
        public ModelAndView dealHandlerExceptionResolver2(Excetption e){
    
            System.out.println("33333"+e.getMessage());
            ModelAndView mv = new ModelAndView();
            mv.addObject("myexception",e.getMessage());
            mv.setViewName("error");
            return mv;
        }
    }

![1222878-20171104123327701-144783387.png][]

#### 3.2 `@ControllerAdvice` ####

*  将所有异常存放在 `exception` 包下,将业务方法和处理异常的方法分离;
 *  @ExceptionHandler中找不到的话,就去`@ControllerAdvice`标记的类里面查找标记了  
    @ExceptionHandler的方法;

// cn.itcast.springmvc.exception.CommonHelperException 类
    
    @ControllerAdvice
    public class CommonHelperException{
        @ExceptionHandler(value={ArithmeticException.class})
        public ModelAndView dealHandlerExceptionResolver(Excetption e){
    
            System.out.println("44444"+e.getMessage());
            ModelAndView mv = new ModelAndView();
            mv.addObject("myexception",e.getMessage());
            mv.setViewName("error");
            return mv;
        }
    }

#### 3.3 ReponseStatusExceptionResolver ####

// 模拟账户锁定,自定义一个 MyUserLockException 继承了 RuntimeException 的异常类
    
    // index.jsp
    账户锁定异常:
    <a href="${pageContext.request.contextPath}/testResponse?username=lisi">异常示例</a>
    
    
    // cn.itcast.springmvc.exception.MyUserLockException 类
    @ResponseStatus(value=HttpStatus.LOCKED,reason="账户被锁定,请拨打10086")
    public class MyUserLockException extends RuntimeException{
        private static final long serialVersionUID = 1L;
    }
    
    // Demo.java
    @Controller
    public class Demo{
        @RequestMapping(value="/testResponse",method=RequestMethod.GET)
        public String testResponse(@RequestParam("username") String username){
    
            // username=zhangsan, 抛出异常
            if("zhangsan".equalsIgnoreCase(username)){
                throw new MyUserLockException();
            }
            return "ok";
        }
    
        //第二种用法,@ResponseStatus 用在方法上
        // 如果 name=zhangsan, 报 MyUserLockException,
        // 如果 name 为其他,报 Not Found
        @RequestMapping(value="/testResponse",method=RequestMethod.GET)
        @ResponseStatus(value=HttpStatus.NOT_FOUND,reason="测试...")
        public String testResponse(@RequestParam("username") String username){
    
            // username=zhangsan, 抛出异常
            if("zhangsan".equalsIgnoreCase(username)){
                throw new MyUserLockException();
            }
            return "ok";
        }
    }

![1222878-20171104123350951-1599260766.png][]

![1222878-20171104123401779-21668157.png][]

#### 3.4 SimpleMappingExceptionResolver ####

// 示例: 数组下标越界异常
    
    // springDispatcherServlet-servlet.xml 配置
    <bean id="simpleMappingExceptionResolver"
        class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
    
        <!-- 可以自定义 requestScope.异常名称 --
        <property name="exceptionAttribute" value="自定义异常名称"/>
    
        <property name="exceptionMappings">
        <props>
            <prop key="java.lang.ArrayIndexOutOfBoundsException">error</prop>
        </props>
        </property>
    </bean>
    
    // index.jsp
    异常示例:<a href="${pageContext.request.contextPath}/testSimple?id=3">数组下标越界</a>
    
    // error.jsp
    <body>
    抱歉,系统繁忙,请稍候在试!<br/>
    数组下标越界:${requestScope.exception}<br/>
    </body>
    
    // Demo.java
    @Controller
    public class Demo{
        @RequestMapping(value="/testSimple",method=RequestMethod.GET)
        public String testSimple(@RequestParam("id") Integer id){
    
            int[] arr = new int[10];
            System.out.println(arr[id]);
            return "ok";
        }
    }

![1222878-20171104123418998-132266875.png][]

[20180505194621498]: /images/20220525/30c4dc5977dd494782569915bb4e74ba.png
[1222878-20171104123209451-2127638057.png]: /images/20220525/6e25558ae93a4cf2b0c17f73c3e9196f.png
[1222878-20171104123230951-845925520.png]: /images/20220525/fa1aadb53f3d4887adeb98aeeca37307.png
[1222878-20171104123240873-1170080086.png]: /images/20220525/24511719c7b84f97bf6ffcd6949801ef.png
[1222878-20171104123259732-1490369580.png]: /images/20220525/8b0170506cd349f3bf3e57499fa05fb3.png
[1222878-20171104123327701-144783387.png]: /images/20220525/372f25a277fb442f86217227e3b0443a.png
[1222878-20171104123350951-1599260766.png]: /images/20220525/874bda257ea740ca97b0516a07af761b.png
[1222878-20171104123401779-21668157.png]: /images/20220525/69f19e276ba2476c8045728fc30735c7.png
[1222878-20171104123418998-132266875.png]: /images/20220525/da2d16ea1f604ef2b641ce4eceffd2ad.png