SpringMVC 上传下载异常处理

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上一章节对SpringMVC的表单验证进行了详细的介绍，本章节介绍SpringMVC文件的上传和下载（重点），国际化以及异常处理问题。这也是SpringMVC系列教程中的最后一节，文章底部会提供该系列的源码地址。

首先看效果图（文件上传，下载和异常处理）

文件上传和下载是需要两个jar包： commons-fileupload.jar 和 commons-io.jar

<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.springmvc</groupId> <artifactId>springmvc</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>war</packaging>  <build> <plugins> <plugin> <artifactId>maven-compiler-plugin</artifactId> <configuration> <source>1.7</source> <target>1.7</target> <encoding>UTF-8</encoding> </configuration> </plugin> </plugins> </build> <properties> <spring.version>4.1.3.RELEASE</spring.version> </properties> <dependencies>  <dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-aop</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-web</artifactId> <version>${spring.version}</version> </dependency>  <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>4.0.0</version> <scope>provided</scope> </dependency> <dependency> <groupId>javax.servlet</groupId> <artifactId>jstl</artifactId> <version>1.2</version> </dependency> <dependency> <groupId>taglibs</groupId> <artifactId>standard</artifactId> <version>1.1.2</version> </dependency>  <dependency> <groupId>javax.servlet.jsp</groupId> <artifactId>jsp-api</artifactId> <version>2.2</version> <scope>provided</scope> </dependency>  <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-validator</artifactId> <version>5.4.1.Final</version> </dependency> <dependency> <groupId>javax.validation</groupId> <artifactId>validation-api</artifactId> <version>1.1.0.Final</version> </dependency>   <dependency> <groupId>commons-fileupload</groupId> <artifactId>commons-fileupload</artifactId> <version>1.3.1</version> </dependency> <dependency> <groupId>commons-io</groupId> <artifactId>commons-io</artifactId> <version>2.4</version> </dependency>  </dependencies> </project>

SpringMVC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.itdragon.springmvc" />  <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="prefix" value="/WEB-INF/views/"></property> <property name="suffix" value=".jsp"></property> </bean>  <mvc:annotation-driven />  <bean class="org.springframework.web.servlet.view.BeanNameViewResolver"> <property name="order" value="100"></property> </bean>  <mvc:view-controller path="/index" view-name="index"/> <mvc:default-servlet-handler/>  <bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource"> <property name="basename" value="i18n"></property> </bean>  <bean id="localeResolver" class="org.springframework.web.servlet.i18n.SessionLocaleResolver"></bean>  <mvc:interceptors> <bean id="localeChangeInterceptor" class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor"></bean> </mvc:interceptors>  <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"> <property name="defaultEncoding" value="UTF-8"></property> <property name="maxUploadSize" value="2048000"></property> </bean>  <bean id="simpleMappingExceptionResolver" class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">  <property name="exceptionAttribute" value="exception"></property> <property name="exceptionMappings"> <props>  <prop key="java.lang.ArrayIndexOutOfBoundsException">exception</prop> </props> </property> </bean> </beans>

FileUploadController.java 文件上传，下载和国际化知识点

国际化步骤

第一步，在SpringMVC配置文件中配置 SessionLocaleResolver（bean的id必须是localeResolver）和 LocaleChangeInterceptor（bean放在mvc:interceptors 拦截器中）两个bean。

第二步，视图页面引入 fmt 标签，并用 <fmt:message key="xxx" /> 设置值。

第三步，语言切换的链接，其格式：English。

第四步，创建链接的目标方法，其参数为Locale 类型参数。

第五步，准备语言文件，i18n_en_US.properties 和 i18n_zh_CN.properties，配置xxx的对应语言。

文件上传和下载

第一步，在SpringMVC配置文件中配置 CommonsMultipartResolver，并设置默认编码格式和最大尺寸

第二步，视图页面创建一个form表单，并设置 enctype="multipart/form-data"

第三步，目标方法接收参数的类型为 MultipartFile ，然后是文件流的操作。

第四步，看代码吧！

import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.util.Locale; import java.util.Map; import javax.servlet.ServletContext; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpSession; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.support.ResourceBundleMessageSource; import org.springframework.http.HttpHeaders; import org.springframework.http.HttpStatus; import org.springframework.http.ResponseEntity; 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 public class FileUploadController { @Autowired private ResourceBundleMessageSource messageSource; /** * 国际化 * 第一步，在SpringMVC配置文件中，配置 SessionLocaleResolver 和 LocaleChangeInterceptor * 第二步，准备语言文件，i18n_en_US.properties 和 i18n_zh_CN.properties * 第三步，目标方法中，参数加入Locale对象。 */ @RequestMapping("/fileUpload") public String fileUpload(Locale locale) { // String val = messageSource.getMessage("file", null, locale); // System.out.println(val); return "fileUpload"; } // MultipartFile 上传文件必用的变量类型 @RequestMapping("/testFileUpload") public String testFileUpload(@RequestParam("desc") String desc, @RequestParam("file") MultipartFile file, Map<String, Object> map, HttpServletRequest request) { InputStream in = null; OutputStream out = null; String fileName = file.getOriginalFilename(); // 获取文件名 try { String realPath = request.getServletContext().getRealPath("uploads/"); in = file.getInputStream(); byte[] buffer = new byte[1024]; String filePath = realPath + "/" + fileName; // 文件上传路径 out = new FileOutputStream(filePath); int len = 0; while ((len = in.read(buffer)) != -1) { out.write(buffer, 0, len); } } catch (IOException e) { e.printStackTrace(); } finally { try { if (null != out) { out.close(); } if (null != in) { in.close(); } } catch (IOException e) { e.printStackTrace(); } } map.put("fileName", fileName); return "fileUpload"; } // 不适合大文件的下载，适用于简单的下载场景。 @RequestMapping("/downLoadFile") public ResponseEntity<byte[]> downLoadFile(@RequestParam("fileName") String fileName, HttpSession session) { byte [] body = null; ServletContext servletContext = session.getServletContext(); InputStream in = null; ResponseEntity<byte[]> response = null; try { in = servletContext.getResourceAsStream("/uploads/"+fileName); body = new byte[in.available()]; in.read(body); HttpHeaders headers = new HttpHeaders(); headers.add("Content-Disposition", "attachment;filename="+fileName); HttpStatus statusCode = HttpStatus.OK; response = new ResponseEntity<byte[]>(body, headers, statusCode); } catch (IOException e) { e.printStackTrace(); } finally { try { if (null != in) { in.close(); } } catch (IOException e) { e.printStackTrace(); } } return response; } }

fileUpload.jsp 文件上传下载前端页面

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %> <%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %> <!DOCTYPE> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>SpringMVC 快速入门</title> <link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"> </head> <body> <div class="container"> <div class="row"> <div class="col-sm-6"> <div class="panel panel-info" style="margin-top:10px;"> <div class="panel-heading"> <h3 class="panel-title"><fmt:message key="file.upload" /></h3> </div> <div class="panel-body">  <form action="${pageContext.request.contextPath }/testFileUpload" method="POST" enctype="multipart/form-data"> <div class="form-group"> <label class="col-sm-2 control-label"><fmt:message key="file" /></label> <div class="col-sm-10"> <input type="file" name="file" class="form-control" /> </div> </div> <div class="form-group"> <label class="col-sm-2 control-label"><fmt:message key="desc" /></label> <div class="col-sm-10"> <input type="text" name="desc" class="form-control" /> </div> </div> <input type="submit" value="Submit" class="btn btn-success" /> </form> <a href="fileUpload?locale=zh_CN" class="btn" >中文</a> <a href="fileUpload?locale=en_US" class="btn" >English</a> </div> </div> </div> <hr /> <a href="downLoadFile?fileName=${fileName}" >${fileName}</a> <hr /> </div> </div> </body> </html>

常用的三种异常处理

@ExceptionHandler 注解

第一步，创建一个用注解@ControllerAdvice 修饰的切面类（也可以是普通类）。

第二步，创建一个目标方法，并用注解@ExceptionHandler 修饰，value值是一个数组，值是异常类。

第三步，目标方法的的参数必须有Exception 类型的参数，用于获取运行时发生的异常。

第四步，目标方法若想把异常返回给页面，可以用ModelAndView 类型作为返回值，而不能用Map作为参数返回。

@ResponseStatus 注解

第一步，创建一个被注解@ResponseStatus 修饰的自定义异常类，value值是状态码，reason值是字符串。

第二步，在目标方法执行时抛出自定义异常。

SimpleMappingExceptionResolver Bean

第一步，在SpringMVC的配置文件中配置Bean SimpleMappingExceptionResolver 。

第二步，设置exceptionAttribute 模型Model，必须和页面上的值一致。

第三步，设置exceptionMappings 视图View，只有当异常触发时跳转到视图页面。

注意细节，看代码

StudyExceptionHandlerAdvice.java 切面类

import org.springframework.web.bind.annotation.ControllerAdvice; import org.springframework.web.bind.annotation.ExceptionHandler; import org.springframework.web.servlet.ModelAndView; /** * 1 @ExceptionHandler 注解修饰的方法可以放在普通类中，也可以放在切面类中(@ControllerAdvice 注解修饰的类)。前者表示只处理当前类的异常，后者表示处理全局的异常。 * 2 @ExceptionHandler 注解修饰的方法参数中，不能有Map，否则会提示：。若希望把异常信息返回给前端，可以使用ModelAndView * 3 @ExceptionHandler 注解修饰的多个方法中，优先级原则是就近原则(和异常精度越近的异常，优先执行)。 */ @ControllerAdvice public class StudyExceptionHandlerAdvice { @ExceptionHandler({ArithmeticException.class}) public ModelAndView handleArithmeticException(Exception exception){ System.out.println("ArithmeticException 出异常了: " + exception); ModelAndView mv = new ModelAndView("exception"); mv.addObject("exception", "ArithmeticException 出异常了: " + exception); return mv; } /*@ExceptionHandler({RuntimeException.class}) public ModelAndView handleRuntimeException(Exception exception){ System.out.println("RuntimeException 出异常了: " + exception); ModelAndView mv = new ModelAndView("exception"); mv.addObject("exception", "RuntimeException 出异常了: " + exception); return mv; }*/ }

ResponseStatusException.java 自定义异常类

import org.springframework.http.HttpStatus; import org.springframework.web.bind.annotation.ResponseStatus; @ResponseStatus(value = HttpStatus.BAD_REQUEST, reason = "ResponseStatusException : 自定义异常原因") public class ResponseStatusException extends RuntimeException{ }

StudyExceptionController.java 异常处理测试类

import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestParam; @Controller public class StudyExceptionController { @RequestMapping("/exception") public String exception(){ return "exception"; } @RequestMapping("/simpleMappingExceptionResolver") public String simpleMappingExceptionResolver(@RequestParam("num") int num){ String [] args = new String[10]; System.out.println("通过配置bean，来处理某一种异常导致的所有问题。" + args[num]); return "exception"; } @RequestMapping(value="/testResponseStatus") public String testResponseStatus(@RequestParam("num") Integer num){ System.out.println("@ResponseStatus 自定义异常"); if (0 == num) { throw new ResponseStatusException(); } return "exception"; } @RequestMapping("/testExceptionHandler") public String testExceptionHandler(@RequestParam("num") Integer num){ System.out.println("@ExceptionHandler - result: " + (10 / num)); return "exception"; } }

exception.jsp 异常处理前端页面

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>SpringMVC 快速入门</title> <link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"> </head> <body> <div class="container"> <div class="row"> <h2>SpringMVC 异常处理</h2> <hr/> @ExceptionHandler : <a href="testExceptionHandler?num=0" class="btn" >testExceptionHandler?num=0</a> <hr/> SimpleMappingExceptionResolver : <a href="simpleMappingExceptionResolver?num=20" class="btn" >simpleMappingExceptionResolver?num=20</a> <hr/> @ResponseStatus : <a href="testResponseStatus?num=0" class="btn" >testResponseStatus?num=0</a> <hr/> ${exception} </div> </div> </body> </html>