SpringMVC框架（四）文件的上传下载，上下文路径

文件目录：

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:mvc="http://www.springframework.org/schema/mvc"
     xmlns:context="http://www.springframework.org/schema/context"
     xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.3.xsd
         http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
         http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd">

     <!-- 配置扫描器 -->
     <context:component-scan base-package="com.maya.comtroller" />

     <!-- 配置视图解析器 -->
     <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
         <!-- <property name="prefix" value="/WEB-INF/"></property> -->
         <property name="prefix" value="/"></property>
         <property name="suffix" value=".jsp"></property>
     </bean>

     <!-- 对于上传文件的解析器 -->
     <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
         <!-- 上传文件的最大值, 单位是b -->
         <property name="maxUploadSize" value="10240000"></property>
         <!-- 上传的单个文件的大小限制 -->
         <property name="maxUploadSizePerFile" value="1024000"></property>
         <!-- 转换字符集 -->
         <property name="defaultEncoding" value="utf-8"></property>
     </bean>

     <!-- 开启SpringMVC注解驱动 -->
     <mvc:annotation-driven>
         <!-- 改成false, 原因是在spring中默认使用的json格式的转换器是Jackson.jar中的转换器, 但实际开发中更受欢迎的是fastjson.jar -->
         <mvc:message-converters register-defaults="false">
             <bean class="org.springframework.http.converter.StringHttpMessageConverter" />
             <bean class="org.springframework.http.converter.xml.XmlAwareFormHttpMessageConverter" />
             <bean class="org.springframework.http.converter.BufferedImageHttpMessageConverter" />
             <bean class="org.springframework.http.converter.ByteArrayHttpMessageConverter"/>
             <bean id="fastJsonHttpMessagerConverter" class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter">
                 <!-- 设置支持的媒体类型 -->
                 <property name="supportedMediaTypes">
                     <list>
                         <value>text/html; charset=utf-8</value>
                         <value>application/json; charset=utf-8</value>
                     </list>
                 </property>
             </bean>
         </mvc:message-converters>
     </mvc:annotation-driven>
 </beans>

controller层：

 package com.maya.comtroller;

 import java.io.File;
 import java.io.IOException;
 import java.util.Date;

 import javax.servlet.http.HttpServletRequest;

 import org.apache.commons.io.FileUtils;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 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
 @RequestMapping("file")
 //上传文件
 public class TestFileController {
     @RequestMapping("/testUpload")
     public String testUpload(
             HttpServletRequest request,
             @RequestParam("myfile")
             MultipartFile file,
             String desp) throws IllegalStateException, IOException {

         String path =
                 request.getServletContext().getRealPath("/MyFiles/");

         Date date = new Date();

         String orgFileName = date.getTime()+ "";

         String typeName = file.getOriginalFilename();

         String orgTypeName = typeName.substring(typeName.lastIndexOf("."));

         System.out.println(path);
         // 上传文件的源文件名
         File orgFile = new File(path + "/" + orgFileName + orgTypeName);

         file.transferTo(orgFile);

         return "success";
     }

     //下载文件
     @RequestMapping("/downloadFile")
     public ResponseEntity<byte[]> testDownLoad(
             HttpServletRequest request,
             String filename) throws Exception {

         String orgFilename = new String(filename.getBytes("iso-8859-1"), "utf-8");

         String path =
                 request.getServletContext().getRealPath("/myfiles/");

         File orgFile = new File(path + "/" + orgFilename);

         // 设置请求头信息
         HttpHeaders hh = new HttpHeaders();
         // 告诉前台, 以(attachement, 就是下载)的方式打开文件
         hh.setContentDispositionFormData("attachment", new String(orgFilename.getBytes("utf-8"), "iso-8859-1"));
         // 以二进制流的形式传输文件, 这是最常见的下载方式
         hh.setContentType(MediaType.APPLICATION_OCTET_STREAM);

         return new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(orgFile), hh,
                 HttpStatus.CREATED);
     }

 }

jsp页面：

 <%@ page language="java" contentType="text/html; charset=utf-8"
     pageEncoding="utf-8" import="java.io.File"%>
 <!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>
 <div style="margin:100px">
 <form action="file/testUpload.do" method="post" enctype="multipart/form-data">
     <input name="desp" />
     <input type="file" multiple="multiple" name="myfile" /><br>
     <input type="submit" value="Submit" />
 </form>

 <hr>
 <%
     String path = request.getServletContext().getRealPath("/MyFiles/");
     File f = new File(path);
     File[] files=f.listFiles(); //获取路径下的文件名
     for(File fi:files){
         out.print("<a href='file/downloadFile.do?filename="+fi.getName()+"'>"+fi.getName()+"</a><br>");
     }
 %>
 </div>
 </body>
 </html>

这种方式只能进行单文件的上传，不建议使用该方式进行多文件上传，应考虑其他方式。如果要使用该方式进行多文件上传，可以，使用如下代码：

from表单中增加一个

multiple="multiple"

     <form action="<%=basePath %>/file/testUpload.do" method="post"
         enctype="multipart/form-data">
         <input name="myfile" multiple="multiple" type="file" /><input type="submit"
             value="Submit" />
     </form>

后台：

 @Controller
 @RequestMapping("file")
 public class TestFileController {
     @RequestMapping("/testUpload")
     public String testUpload(
             HttpServletRequest request,
             @RequestParam("myfile")
             MultipartFile[] files,
             String desp) throws IllegalStateException, IOException {

         String path =
                 request.getServletContext().getRealPath("/files/");

         for(MultipartFile file : files) {
             Date date = new Date();
             String orgFileName = date.getTime()+ "";
             String typeName = file.getOriginalFilename();
             String orgTypeName = typeName.substring(typeName.lastIndexOf("."));
             File orgFile = new File(path + "/" + orgFileName + orgTypeName);
             file.transferTo(orgFile);
         }
     }

但是，如果在上传成功之后的提示页面通过超链接返回文件上传页面，会报404错

因为有注解

@RequestMapping("file")

定义了请求的前缀是指向 file 下的，所以执行方法最后返回的时候，会从 file 下去寻找视图层的页面，所以无法找到

解决方法：

可以通过上下文路径：

 <%
     String basePath = request.getContextPath(); // 上下文路径
 %>

     <%=basePath %>

获取当前项目名，并写在请求的路径中

 <%@ 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>
 <%
     String basePath = request.getContextPath(); // 上下文路径
 %>
 </head>
 <body>
 上传成功 !
 <a href="<%=basePath %>/filetest.jsp">返回文件页面</a>
 </body>
 </html>