Java_常瑞鹏 实现文件上传与下载
文件下载
因为要下载的文件可以是各种类型的文件，所以要将文件传送给客户端，其相应内容应该被当做二进制来处理，所以应该调用 方法返回 ServeltOutputStream对象来向客户端写入文件内容。
下载案例
遍历上传目录下的所有文件显示给用户，并允许用户完成下载。
（读取某一个文件夹下的所有的文件，存到集合里面List，再存到request作用域范围中）ListFileServelt—（将所有的文件列表显示）Listfiles.jsp-----DownloaServlet.java
private String id;
private String savename; //上传文件的名称，文件的uuid名
private String realName; //上传文件的真实名称
private String savepath; //记住文件的位置
private Date uptime; //文件的上传时间
private String description; //文件的描述
private String username; //上传人
ListFileServlet
package com.hbsi.servlet;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
public class ListFileServlet extendsHttpServlet {
publicvoid doGet(HttpServletRequest request, HttpServletResponse response)
throwsServletException, IOException {
Stringsavepath = this.getServletContext().getRealPath(
"/WEB-INF/upload");
Mapmap = new HashMap();
listFiles(newFile(savepath), map);
request.setAttribute("map",map);
request.getRequestDispatcher("/listfile.jsp")
.forward(request,response);
}
privatevoid listFiles(File file, Map map) {
if(file.isFile()) {
Stringuuidname = file.getName(); // uuid_a_1_3_3.txt
Stringrealname = uuidname.substring(uuidname.indexOf("_") + 1);
map.put(uuidname,realname);
}else {
File[]files = file.listFiles();
for(File f : files) {
listFiles(f,map);
}
}
}
publicvoid doPost(HttpServletRequest request, HttpServletResponse response)
throwsServletException, IOException {
doGet(request,response);
}
}
DownloadServlet
package com.hbsi.servlet;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.URLEncoder;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
public class DownloadServlet extendsHttpServlet {
publicvoid doGet(HttpServletRequest request, HttpServletResponse response)
throwsServletException, IOException {
Stringfilename = request.getParameter("filename");
filename= new String(filename.getBytes("iso8859-1"), "utf-8");
System.out.println(filename);
Stringsavepath = this.getFileSavePath(this.getRealName(filename));
Filef = new File(savepath + "\\" + filename);
if(!f.exists()) {
request.setAttribute("message","下载的资源不存在");
request.getRequestDispatcher("/message.jsp").forward(request,response);
}
response.setHeader("content-disposition","attachment;filename="+ URLEncoder.encode(this.getRealName(filename),"UTF-8"));
FileInputStreamin = new FileInputStream(f);
byte[]buf = new byte[1024];
intlen = 0;
OutputStreamout = response.getOutputStream();
while((len = in.read(buf)) > 0) {
out.write(buf,0, len);
}
in.close();
}
publicString getFileSavePath(String filename) {
intdir1 = filename.hashCode() & 0xf;
intdir2 = (filename.hashCode() >> 4) & 0xf;
Stringsavepath = this.getServletContext().getRealPath("/WEB-INF/upload")+"\\" + dir1 + "\\" + dir2;
returnsavepath;
}
publicString getRealName(String filename) {
StringrealName = filename.substring(filename.indexOf("_") + 1);
returnrealName;
}
publicvoid doPost(HttpServletRequest request, HttpServletResponse response)
throwsServletException, IOException {
doGet(request,response);
}
}
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