Java Web实用开发技术-文件的上传与下载
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2022-07-12 19:00:38
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（需要将cos.jar放入lib目录下）
文件上传页面upload.jsp
<%@ 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>
<form action="upload" method="post" enctype="multipart/form-data">
<input type="file" name="file1"><br>
<input type="submit" value="上传">
</form>
</body>
</html>
执行上传操作的Servlet(地址为upload)
package Servlet;
import java.io.File;
import java.io.IOException;
import java.util.Enumeration;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.oreilly.servlet.MultipartRequest;
/**
* Servlet implementation class UploadServlet
*/
@WebServlet("/upload")
public class UploadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public UploadServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String saveDirectory="d:\\tools\\upload";//即上传到服务器的D盘目录
File savedir=new File(saveDirectory);
if(!savedir.exists()){
savedir.mkdirs();//若路径不存在，则创建它
}
int maxPostSize=5*1024*1024;//上传大小限制：5MB
//若上传的文件重名，则默认覆盖原先的文件
MultipartRequest multi;
multi=new MultipartRequest(request,saveDirectory,maxPostSize,"utf-8");
/*
* 下述代码若上传的文件重名，会自动为新文件重新命名（文件名后加序号01，02...）
* FileRenamePolicy policy=(FileRenamePolicy)new DefaultFileRenamePolicy();
* MultipartRequest multi;
* multi=new MultipartRequest(request,saveDirectory,maxPostSize,"utf-8");
*/
//若想获得上传的文件和表单的其他元素的信息，可借助于MultipartRequest类型的对象multi
//在控制台上显示文件信息
Enumeration<String> files=multi.getFileNames();
while(files.hasMoreElements()){
String name=files.nextElement();
File f=multi.getFile(name);
if(f!=null){
String fileName=multi.getFilesystemName(name);
String lastFileName=saveDirectory+"\\"+fileName;
System.out.println("上传的文件："+lastFileName);
}
}
}
}
执行下载操作的Servlet(地址为download)
package Servlet;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.oreilly.servlet.ServletUtils;
/**
* Servlet implementation class DownloadServlet
*/
@WebServlet("/download")
public class DownloadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public DownloadServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String filepath="d:/";//下载路径
String filename="1.jpg";//下载的文件名
String guessCharset="UTF-8";
try{//使用iso-8859-1编码方式
String isofilename=new String(filename.getBytes(guessCharset),"iso-8859-1");
response.setContentType("application/octet-stream");
response.setHeader("Content-Disposition", "attachment;filename"+isofilename);
ServletOutputStream out=null;
out=response.getOutputStream();
ServletUtils.returnFile(filepath+filename,out);//下载文件
}catch(UnsupportedEncodingException ex){//iso8859_1编码异常
ex.printStackTrace();
}catch(IOException e){//getOutputStream()异常
e.printStackTrace();
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
}
【实例】上传作业，上传的作业命名格式为“学号-题号”，要求上传到服务器后将文件重命名为“客户端IP地址-学号-题号”形式，可上传多次，后上传的文件将覆盖先前上传的文件。
上传页面upload.jsp代码
<%@ 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>
<form action="Upload" method="post" enctype="multipart/form-data">
<input type="file" name="file1" contenteditable="false"
onclick="info.innerHTML=''"><br>
<input type="submit" value="上传">
</form>
<div id="info">${message }</div>
</body>
</html>
处理上传的Servlet（地址为Upload）
package Servlet;
import java.io.File;
import java.io.IOException;
import java.util.Enumeration;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.oreilly.servlet.MultipartRequest;
/**
* Servlet implementation class Upload
*/
@WebServlet("/Upload")
public class Upload extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public Upload() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String requestip=request.getRemoteAddr();
String saveDirectory=this.getServletContext().getRealPath("")+"\\Upload";
File savedir=new File(saveDirectory);
if(!savedir.exists()){
savedir.mkdirs();//若路径不存在，则创建它
}
int maxPostSize=5*1024*1024;//上传大小限制：5MB
//若上传的文件重名，则默认覆盖原先的文件
MultipartRequest multi;
multi=new MultipartRequest(request,saveDirectory,maxPostSize,"utf-8");
Enumeration<String> files=multi.getFileNames();
String name=files.nextElement();
File f=multi.getFile(name);
if(f!=null){
String fileName=f.getName();
File sServerFile=new File(saveDirectory+"\\"+requestip+"-"+fileName);
if(sServerFile.exists()){
sServerFile.delete();
}
f.renameTo(sServerFile);
String message="文件上传成功！文件名为："+requestip+"-"+fileName;
request.setAttribute("message", message);
}
request.getRequestDispatcher("/upload.jsp").forward(request, response);
}
}