通过JSP+servlet实现文件上传功能

时间：2023-03-08 16:52:37

在TCP/IP中，最早出现的文件上传机制是FTP.它将文件由客户端到服务器的标准机制。

但是在JSP中不能使用FTP来上传文件，这是有JSP的运行机制所决定的。

通过为表单元素设置Method="post" enctype="multipart/form-data" 属性，让表单提交的数据以二进制编码的方式提交，在接受此请求的servlet中的二进制流来获取内容，就可以取得上传文件的内容，从而实现文件的上传。

代码分两部分

part1:前台页面index.jsp

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

<html>

  <head>

  </head>

  <body>

    <form action="UploadFile" method="post" enctype="multipart/form-data">

    <table>

    <tr>

    <td align="center">

               请选择上传的文件:<input type="file" name="fileName"/>
               &nbsp;&nbsp;<input type="submit" value="上传"/>${result}
    </td>

    </tr>

     </table>

    </form>

  </body>

</html>

part2:servlet代码

package com.file;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.PrintWriter;

import java.io.RandomAccessFile;

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class UploadFile extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

        throws ServletException, IOException {

        doPost(request,response);

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

        throws ServletException, IOException {

        //写入缓存文件

        InputStream fileSource=request.getInputStream();

        String tempFileName="E:/tempFile";

        File tempFile=new File(tempFileName);

        FileOutputStream outputStram=new FileOutputStream(tempFile);

        byte[] b=new byte[1024];

        int n;

        while((n=fileSource.read(b))!=-1){

            outputStram.write(b,0,n);

        }

        outputStram.close();

        fileSource.close();

        System.out.println("成功");

        //获取文件名

        RandomAccessFile randomFile=new RandomAccessFile(tempFile,"r");

        randomFile.readLine();

        String str=randomFile.readLine();

        int beginIndex=str.lastIndexOf("\\")+1;

        int endIndex=str.lastIndexOf("\"");

        String filename=str.substring(beginIndex, endIndex);

        System.out.println("filename:"+filename);

        //获取上传文件内容的开始位置

        randomFile.seek(0);

        long startPosition=0;

        int i=1;

        while((n=randomFile.readByte())!=-1&&i<=4){

            if(n=='\n'){

                startPosition=randomFile.getFilePointer();

                i++;

            }

        }

        startPosition=startPosition-1;



        //获取上传文件内容的结束位置      
        randomFile.seek(randomFile.length());

        long endPosition=randomFile.getFilePointer();

        int j=1;

        while(endPosition>=0&&j<=2){

            endPosition--;

            randomFile.seek(endPosition);

            if(randomFile.readByte()=='\n'){

                j++;

               }

        }

        endPosition=endPosition-1;



        //上传文件

        String path=getServletContext().getRealPath("/")+"MyImages"; //指定上传文件的目录
        File fileupload=new File(path);

        if(!fileupload.exists()){

             fileupload.mkdir();

        }

        File saveFile=new File(path,filename);

        RandomAccessFile RAF=new RandomAccessFile(saveFile,"rw");

        randomFile.seek(startPosition);

        while(startPosition<endPosition){

            RAF.write(randomFile.readByte());

            startPosition=randomFile.getFilePointer();

        }

        RAF.close();

        randomFile.close();

        tempFile.delete();

        request.setAttribute("result","上传成功!");

        RequestDispatcher dispatcher=request.getRequestDispatcher("index.jsp");

        dispatcher.forward(request,response);

    }

}

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