Java上传文件

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1.首先创建一个Javaweb项目（idea）

2.建一个简单的jsp页面

<%--  Created by IntelliJ IDEA.  User: Administrator  Date: 2017/12/5  Time: 11:36  To change this template use File | Settings | File Templates.--%><%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>Title</title></head><body><form id="form" name="form" method="post" enctype="multipart/form-data" action="uploadServlet.do" >    上传的文件：<input id="file" name="file" type="file"/>    <button type="submit" name="btn" id="btn">提交</button></br>${result}</form></body></html>

注意：form表单中需要添加一个属性和它的值 enctype="multipart/form-data"，input属性的type设为file

3.创建一个servlet

package com.zj.servlet;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 java.io.*;@WebServlet(name = "uploadServlet")public class uploadServlet extends HttpServlet {    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        System.out.println("开始上传文件");        //获取前台传过来的文件信息        InputStream  filestram=request.getInputStream();        //设置读取文件的编码格式        InputStreamReader inputStreamReader=new InputStreamReader(filestram,"utf-8");        //将传过来的文件信息保存在临时文件中去        String tempFile="E:/tempfile";        File file =new File(tempFile);        //将上传信息写入到临时文件中去        FileOutputStream fileOutputStream=new FileOutputStream(file);        //设置写入文件的编码格式        OutputStreamWriter outputStreamWriter=new OutputStreamWriter(fileOutputStream,"utf-8");        //循环读取上传上来的文件内容 ，并写入临时文件        byte[] b=new byte[1024];        int n;        while ((n=filestram.read(b))!=-1){            fileOutputStream.write(b,0,n);        }        //关闭输入输出流        fileOutputStream.close();        filestram.close();        //获取上传文件的名称        RandomAccessFile randomAccessFile=new RandomAccessFile(tempFile,"r");        randomAccessFile.readLine();        String str=randomAccessFile.readLine();        int beginIndex=str.lastIndexOf("=")+2;//文件不要放在桌面上        System.out.println("beginIndex="+beginIndex);        int endIndex=str.lastIndexOf("\"");        System.out.println("endIndex="+endIndex);        String filename= str.substring(beginIndex,endIndex);        //解决获取文件名称乱码        String f=new String(filename.getBytes("ISO-8859-1"),"utf-8");        System.out.println("文件名="+f);        //获取上传文件的内容，并保存在某一路径下        //重新指定文件的指针位置        randomAccessFile.seek(0);        //定义读取文件内容的开始位置        long startposition=0;        int i=1;        //获取读取文件的开始位置        while ((n=randomAccessFile.readByte())!=-1&&i<=4){            if (n=='\n'){                startposition=randomAccessFile.getFilePointer();                i++;            }        }        System.out.println("文件读取的开始位置="+startposition);        startposition=randomAccessFile.getFilePointer()-1;        //获取读取文件的结束位置        //重新指定文件的指针位置        randomAccessFile.seek(randomAccessFile.length());//将指针指向临时问件的结尾        //定义文件的结束位置        long endposition=randomAccessFile.getFilePointer();        int j=1;        while (endposition>=0&&j<=6){            endposition--;            randomAccessFile.seek(endposition);            if (randomAccessFile.readByte()=='\n'){                j++;            }        }        endposition=endposition-1;        System.out.println("endposition="+endposition);        //定义写入文件的路径        String  Path="E:/tempfiles";        //创建写入文件夹        File pathfile=new File(Path);        //判断创建的文件夹是否存在        if (!pathfile.exists()){            pathfile.mkdir();        }        //创建保存文件（pathfile：文件的路径，f：需要读取的临时文件）        File savefile=new File(pathfile,f);        //设置对文件访问的方式为读写        RandomAccessFile  r=new RandomAccessFile(savefile,"rw");        //从临时文件中读取文件内容（根据起止位置获取）        randomAccessFile.seek(startposition);        //循环写入读取文件内容        while (startposition<endposition){           r.write(randomAccessFile.readByte());           startposition=randomAccessFile.getFilePointer();        }        //关闭输入输出流        r.close();        randomAccessFile.close();        file.delete();
//返回信息给页面request.setAttribute("result","上传成功！！");RequestDispatcher requestDispatcher=request.getRequestDispatcher("/01.jsp");requestDispatcher.forward(request, response);
     }    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        doPost(request,response);    }}

4.在web.xml中配置servlet

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"         version="3.1"><servlet>    <servlet-name>uploadServlet</servlet-name>    <servlet-class>com.zj.servlet.uploadServlet</servlet-class></servlet>    <servlet-mapping>        <servlet-name>uploadServlet</servlet-name>        <url-pattern>/uploadServlet.do</url-pattern>    </servlet-mapping>    <welcome-file-list>        <welcome-file>01.jsp</welcome-file>    </welcome-file-list></web-app>

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