Java实现上传和下载功能（支持多个文件同时上传）

时间：2020-12-13来源：www.pcxitongcheng.com作者：电脑系统城

文件上传一直是Web项目中必不可少的一项功能。

项目结构如下：（这是我之前创建的SSM整合的框架项目，在这上面添加文件上传与下载）

主要的是FileUploadController，doupload.jsp,up.jsp,springmvc.xml

1.先编写up.jsp

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6 <form action="doupload.jsp" enctype="multipart/form-data" method="post">
<p>上传者：<input type="text" name="user"></p>
<p>选择文件：<input type="file" name="nfile"></p>
<p>选择文件：<input type="file" name="nfile1"></p>
<p><input type="submit" value="提交"></p>
</form>

以上便是up.jsp的核心代码；

2.编写doupload.jsp

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41 <%
request.setCharacterEncoding("utf-8");
String uploadFileName = ""; //上传的文件名
String fieldName = ""; //表单字段元素的name属性值
//请求信息中的内容是否是multipart类型
boolean isMultipart = ServletFileUpload.isMultipartContent(request);
//上传文件的存储路径（服务器文件系统上的绝对文件路径）
String uploadFilePath = request.getSession().getServletContext().getRealPath("upload/" );
if (isMultipart) {
FileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(factory);
try {
//解析form表单中所有文件
List<FileItem> items = upload.parseRequest(request);
Iterator<FileItem> iter = items.iterator();
while (iter.hasNext()) { //依次处理每个文件
FileItem item = (FileItem) iter.next();
if (item.isFormField()){ //普通表单字段
fieldName = item.getFieldName(); //表单字段的name属性值
if (fieldName.equals("user")){
//输出表单字段的值
out.print(item.getString("UTF-8")+"上传了文件。<br/>");
}
}else{ //文件表单字段
String fileName = item.getName();
if (fileName != null && !fileName.equals("")) {
File fullFile = new File(item.getName());
File saveFile = new File(uploadFilePath, fullFile.getName());
item.write(saveFile);
uploadFileName = fullFile.getName();
out.print("上传成功后的文件名是："+uploadFileName);
out.print("\t\t下载链接:"+"<a href='download.action?name="+uploadFileName+"'>"+uploadFileName+"</a>");
out.print("<br/>");
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
%>

该页面主要是内容是，通过解析request，并设置上传路径，创建一个迭代器，先进行判空，再通过循环来实现多个文件的上传，再输出文件信息的同时打印文件下载路径。

效果图：

3.编写FilterController实现文件下载的功能（相对上传比较简单）：

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20 @Controller
public class FileUploadController {
@RequestMapping(value="/download")
public ResponseEntity<byte[]> download(HttpServletRequest request,HttpServletResponse response,@RequestParam("name") String filename)throws Exception {
//下载显示的文件名，解决中文名称乱码问题
filename=new String(filename.getBytes("iso-8859-1"),"UTF-8");
//下载文件路径
String path = request.getServletContext().getRealPath("/upload/");
File file = new File(path + File.separator + filename);
HttpHeaders headers = new HttpHeaders();
//下载显示的文件名，解决中文名称乱码问题
String downloadFielName = new String(filename.getBytes("iso-8859-1"),"UTF-8");
//通知浏览器以attachment（下载方式）打开图片
headers.setContentDispositionFormData("Content-Disposition", downloadFielName);
//application/octet-stream ：二进制流数据（最常见的文件下载）。
headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
return new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(file),
headers, HttpStatus.CREATED);
}
}

4.实现上传文件的功能还需要在springmvc中配置bean：

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11 <bean id="multipartResolver"
class="org.springframework.web.multipart.commons.CommonsMultipartResolver">

<property name="maxUploadSize">
<value>10485760</value>
</property>

<property name="defaultEncoding">
<value>UTF-8</value>
</property>
</bean>

完整代码如下：

up.jsp

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17 <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>File控件</title>
</head>

<body>
<form action="doupload.jsp" enctype="multipart/form-data" method="post">
<p>上传者：<input type="text" name="user"></p>
<p>选择文件：<input type="file" name="nfile"></p>
<p>选择文件：<input type="file" name="nfile1"></p>
<p><input type="submit" value="提交"></p>
</form>
</body>
</html>

doupload.jsp

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55 <%@ page language="java" pageEncoding="UTF-8"%>
<%@page import="java.io.*,java.util.*"%>
<%@page import="org.apache.commons.fileupload.*"%>
<%@page import="org.apache.commons.fileupload.disk.DiskFileItemFactory" %>
<%@page import="org.apache.commons.fileupload.servlet.ServletFileUpload"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>上传处理页面</title>
</head>
<body>
<%
request.setCharacterEncoding("utf-8");
String uploadFileName = ""; //上传的文件名
String fieldName = ""; //表单字段元素的name属性值
//请求信息中的内容是否是multipart类型
boolean isMultipart = ServletFileUpload.isMultipartContent(request);
//上传文件的存储路径（服务器文件系统上的绝对文件路径）
String uploadFilePath = request.getSession().getServletContext().getRealPath("upload/" );
if (isMultipart) {
FileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(factory);
try {
//解析form表单中所有文件
List<FileItem> items = upload.parseRequest(request);
Iterator<FileItem> iter = items.iterator();
while (iter.hasNext()) { //依次处理每个文件
FileItem item = (FileItem) iter.next();
if (item.isFormField()){ //普通表单字段
fieldName = item.getFieldName(); //表单字段的name属性值
if (fieldName.equals("user")){
//输出表单字段的值
out.print(item.getString("UTF-8")+"上传了文件。<br/>");
}
}else{ //文件表单字段
String fileName = item.getName();
if (fileName != null && !fileName.equals("")) {
File fullFile = new File(item.getName());
File saveFile = new File(uploadFilePath, fullFile.getName());
item.write(saveFile);
uploadFileName = fullFile.getName();
out.print("上传成功后的文件名是："+uploadFileName);
out.print("\t\t下载链接:"+"<a href='download.action?name="+uploadFileName+"'>"+uploadFileName+"</a>");
out.print("<br/>");
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
%>
</body>
</html>

FileUploadController.java

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49 package ssm.me.controller;

import java.io.File;
import java.net.URLDecoder;
import java.util.Iterator;
import java.util.List;

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

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.FileUtils;
import org.junit.runners.Parameterized.Parameter;
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.ui.Model;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;

@Controller
public class FileUploadController {
@RequestMapping(value="/download")
public ResponseEntity<byte[]> download(HttpServletRequest request,HttpServletResponse response,@RequestParam("name") String filename)throws Exception {
//下载显示的文件名，解决中文名称乱码问题
filename=new String(filename.getBytes("iso-8859-1"),"UTF-8");
//下载文件路径
String path = request.getServletContext().getRealPath("/upload/");
File file = new File(path + File.separator + filename);
HttpHeaders headers = new HttpHeaders();
//下载显示的文件名，解决中文名称乱码问题
String downloadFielName = new String(filename.getBytes("iso-8859-1"),"UTF-8");
//通知浏览器以attachment（下载方式）打开图片
headers.setContentDispositionFormData("Content-Disposition", downloadFielName);
//application/octet-stream ：二进制流数据（最常见的文件下载）。
headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
return new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(file),
headers, HttpStatus.CREATED);
}
}

SpringMVC.xml（仅供参考，有的地方不可以照搬）

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36 <?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"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.2.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-4.2.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-4.2.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx.xsd">

<mvc:annotation-driven></mvc:annotation-driven>

<context:component-scan base-package="ssm.me.controller"></context:component-scan>

<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"></bean>
<bean id="multipartResolver"
class="org.springframework.web.multipart.commons.CommonsMultipartResolver">

<property name="maxUploadSize">
<value>10485760</value>
</property>

<property name="defaultEncoding">
<value>UTF-8</value>
</property>
</bean>

</beans>

web.xml（仅供参考，有的地方不可以照搬）

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33 <?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>Student</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>springmvc</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>springmvc</servlet-name>
<url-pattern>*.action</url-pattern>
</servlet-mapping>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring/applicationContext-*.xml</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
</web-app>