纯servlet实现文件上传和下载文件代码,Java代码库,德仔网

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【Java】纯servlet实现文件上传和下载文件
作者:明华 / 发布于2016/12/20/ 708
一、准备材料
1、apache提供的包，效率高，且实用性强：
  ( 1)、commons-fileupload-1.3.1.jar
   (2)、commons-io-2.4.jar
2、 jdk1.6以上

二、上传实现的代码
 1、upload.jsp页面
<%@ page language="Java" import="java.util.*" pageEncoding="GBK"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<html>
  <head>
    <base href="<%=basePath%>">
    <title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">    
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
  </head>
  <body>
    <form action="${pageContext.request.contextPath}/upload" method="post" enctype="multipart/form-data">
<!--enctype属性值的意义-->
application/x-www-form-urlencoded	在发送前对所有字符进行编码（默认）。
multipart/form-data	不对字符编码。当使用有文件上传控件的表单时，该值是必需的。
text/plain	将空格转换为 "+" 符号，但不编码特殊字符。

    <input type="file" name="myfile">
    <input type="text" name="mytext" value="123456"/>
    <input type="text" name="mytext" value="123456"/>
    <input type="submit" value="确认上传">
    </form>
  </body>
</html>

2、servlet代码
package com.test.upload;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.NET.HttpRetryException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
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;

@SuppressWarnings("serial")
public class UploadServerlt extends HttpServlet {
public void service(HttpServletRequest request, HttpServletResponse response)
throws HttpRetryException, IOException {
try {
//解析http请求
boolean isMultipart = ServletFileUpload.isMultipartContent(request);
//解析成功
if (isMultipart == true) {
// 获得磁盘文件条目工厂
FileItemFactory factory = new DiskFileItemFactory();
// 高水平的API文件上传处理，将文件保存在服务器硬盘
ServletFileUpload upload = new ServletFileUpload(factory);
//设置上传的单个文件的大小6M
upload.setSizeMax(6*1024*1024);
//设置上传的总文件的大小40M
upload.setFileSizeMax(40*1024*1024);
//http中的复杂表单元素都被看作是FileItem,所以可以上传多个文件
List<FileItem> fileItemList = upload.parseRequest(request);
//如果表单内容不为空
if (fileItemList != null) {
//遍历内容
for (FileItem fileItem: fileItemList) {
//如果是字符:<input type="text" name="mytext" value="123456"/>
if (fileItem.getFieldName().equalsIgnoreCase("mytext")) {
String text2 = fileItem.getString();
}
//如果是文件:<input type="file" name="myfile">
if (fileItem.getFieldName().equalsIgnoreCase("myfile")) {
InputStream in = fileItem.getInputStream();
//写入指定目录下
FileOutputStream fos = new FileOutputStream("F:/232.zip");
byte[] buffer = new byte[1024];
int length;
while ((length = in.read(buffer)) != -1) {
fos.write(buffer, 0, length);
}
in.close();
fos.close();
//清除应用服务器下的临时文件
fileItem.delete();
}
}
}
request.getRequestDispatcher("/index.jsp").forward(request,response);
}
} catch (Exception e) {
e.printStackTrace();
try {
request.getRequestDispatcher("/error.jsp").forward(request,response);
} catch (ServletException e1) {
e1.printStackTrace();
}
}
}
}

3、web.xml文件
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
xmlns="http://java.sun.com/xml/ns/javaee" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  <!-- 测试上传文件 -->
  <servlet>
  <servlet-name>Upload</servlet-name>
  <servlet-class>com.test.upload.UploadServerlt</servlet-class>
  </servlet>
  <servlet-mapping>
  <servlet-name>Upload</servlet-name>
  <url-pattern>/upload</url-pattern>
  </servlet-mapping>
</web-app>

4、访问地址：http://localhost:8080/TestServer/jsp/upload.jsp
5、点击后成功
三、实现下载的代码
1、DownFileServlet.java
package com.test.downFile;

import java.io.FileInputStream;
import java.io.IOException;

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

@SuppressWarnings("serial")
public class DownFileServlet extends HttpServlet{
public void service(HttpServletRequest request,HttpServletResponse response)throws IOException,ServletException{
//获取下载的文件名称
String downPath=(String)request.getParameter("downPath");
try {
//通过response响应返回给客户端
response.setHeader("Content-Disposition","attachment;filename=\""+new String (downPath.getBytes("GBK"),"ISO8859-1")+"\"");//文件名称
//开始写给客户端
FileInputStream fis=new FileInputStream("F://"+downPath);//注意正则表达式的冲突，所以使用//
byte b[]=new byte[1024];
int length;
while((length=fis.read(b))>0){
response.getOutputStream().write(b,0,length);
}
fis.close();
response.getOutputStream().flush();//最好加上这句话，否则缓存会存在
} catch (Exception e) {
e.printStackTrace();
}
}
}
2.downFile.jsp
<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">    
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
  </head>
  <body>
    <form action="${pageContext.request.contextPath}/downFile" method="post" >
    <!-- 指定路径，实际的项目中应该是从数据库中获取 -->
    <input type="text" name="downPath" value="img.zip"/>
    <input type="submit" value="点击下载">
    </form>
  </body>
</html>
3、web.xml文件配置
<!-- 测试下载文件 -->
  <servlet>
  <servlet-name>DownFile</servlet-name>
  <servlet-class>com.test.downFile.DownFileServlet</servlet-class>
  </servlet>
  <servlet-mapping>
  <servlet-name>DownFile</servlet-name>
  <url-pattern>/downFile</url-pattern>
  </servlet-mapping>
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