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JavaWeb实现文件的上传与下载

程序员文章站 2022-03-27 08:13:50
javaweb实现文件的上传与下载,供大家参考,具体内容如下第一步:导包导入commons-fileupload-1.3.3.jar和commons-io-2.4.jar两个依赖包第二步:编写前端页面...

javaweb实现文件的上传与下载,供大家参考,具体内容如下

第一步:导包

导入commons-fileupload-1.3.3.jar和commons-io-2.4.jar两个依赖包

第二步:编写前端页面

1、提交页面 index.jsp

<%@ page language="java" contenttype="text/html; charset=utf-8"
 pageencoding="utf-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!doctype html>
<html>
 <head>
 <meta charset="utf-8">
 <title>insert title here</title>
 </head>
 <body>
 <form action="${pagecontext.request.contextpath }/fileupload" method="post" enctype="multipart/form-data">
 头像:<input type="file" name="img" accept="image/*"/>
 <input type="submit" value="提交"/>
 </form>
 </body>
</html>

2、结果页面 result.jsp

<%@ page language="java" contenttype="text/html; charset=utf-8"
 pageencoding="utf-8"%>
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>insert title here</title>
</head>
<body>
 <center>
 <a href="${pagecontext.request.contextpath }/download?filename=${filename}" >
 <img alt="xx" src="${src }">
 </a>
 </center>
</body>
</html>

第三步:编写上传和下载代码

1、上传图片 fileupload.java

package cn.yz123123.controller;

import java.io.file;
import java.io.fileoutputstream;
import java.io.ioexception;
import java.io.inputstream;

import javax.servlet.servletexception;
import javax.servlet.annotation.multipartconfig;
import javax.servlet.annotation.webservlet;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import javax.servlet.http.part;

@webservlet("/fileupload")
@multipartconfig
public class fileupload extends httpservlet {
 private static final long serialversionuid = 1l;
 
 protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
 dopost(request, response);
 }

 protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
 //string username = request.getparameter("username");
 part part = request.getpart("img");
 
 //获取文件的真实名称
 string header = part.getheader("content-disposition");
 string realname = header.substring(header.indexof("filename=")+10, header.length()-1);
 
 //获取文件自身流
 inputstream inputstream = part.getinputstream();
 
 //获取file真实路径,如果没有则创建
 string dir = request.getservletcontext().getrealpath("/file/");
 file dirfile = new file(dir);
 //上面只是实例化了一个对象,并没有真正的创建一个文件夹
 if (!dirfile.exists()) {
 dirfile.mkdirs();
 }
 
 //创建文件对象,并用流的形式写在相应的文件夹中
 file file = new file(dir, realname);
 fileoutputstream fileoutputstream = new fileoutputstream(file);
 
 byte[] buf = new byte[1024];
 int len;
 while((len=inputstream.read(buf))!=-1) {
 fileoutputstream.write(buf, 0, len);
 }
 
 fileoutputstream.close();
 inputstream.close();
 
 //以下为测试
 request.setattribute("src", request.getcontextpath()+"/file/"+realname);
 request.setattribute("filename", realname);
 request.getrequestdispatcher("/result.jsp").forward(request, response);
 }
 
}

2、下载图片 filedownload.java

package cn.yz123123.controller;

import java.io.fileinputstream;
import java.io.ioexception;
import java.util.uuid;

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;

@webservlet(urlpatterns = "/download")
public class filedownload extends httpservlet{

 @override
 protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
 string filename = req.getparameter("filename");
 
 //获取文件的真实路径
 string filepath = req.getservletcontext().getrealpath("/file/"+filename);
 
 fileinputstream fileinputstream = new fileinputstream(filepath);
 
 resp.setcharacterencoding("utf-8");
 resp.setheader("content-disposition","attachment;filename="+uuid.randomuuid()+filename);
 
 servletoutputstream outputstream = resp.getoutputstream();
 
 byte[] buf = new byte[1024];
 int len;
 
 while((len=fileinputstream.read(buf))!=-1) {
 outputstream.write(buf, 0, len);
 }
 outputstream.close();
 fileinputstream.close();
 
 }
 
 @override
 protected void dopost(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
 super.doget(req, resp);
 }
}

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持。