servlet文件上传及下载

时间：2023-03-09 05:41:07
servlet文件上传及下载

servlet3.0中提供了对文件上传的直接支持，不需要借助任何第三方上传组件，直接使用Servlet3.0提供的API就能够实现文件上传功能。

servlet 代码：

package ni.jun.yang.servlet;

import java.io.File;

import java.io.IOException;

import java.util.UUID;

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("/Upload")

@MultipartConfig    //必须使用此注解，标志此servlet 支持文件上传

public class Upload extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public Upload() {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //设置请求编码

        request.setCharacterEncoding("utf-8");

        //(part)此类表示在multipart/form-dataPOST请求中收到的部分或表单项 。

        //

        Part part = request.getPart("filename");

        //获取上下文对象，再获取某文件夹的位置

        String path = request.getServletContext().getRealPath("file");

        //获得头部信息

        String headName = part.getHeader("content-disposition");
　　　　 System.out.println(headName);

        //截取文件后缀名

        String end = headName.substring(headName.indexOf("."), headName.length()-1);

        //随机生成一个文件名，并拼接完整路径

        String filename = path +File.separator+UUID.randomUUID().toString()+end;

        System.out.println(filename);

        //将上传的项目写入磁盘的方便方法。

        part.write(filename);

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doGet(request, response);

    }

}

part接口：http://docs.oracle.com/javaee/6/api/javax/servlet/http/Part.html

html代码：文件上传一定要将enctype的值改为：enctype="multipart/form-data"

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>文件上传</title>

</head>

<body>

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

	<input type="file" name="filename"><br/><br/>

	<input type="submit" value="上传">

	</form>

</body>

</html>

　　

请求头信息：

servlet文件上传及下载

效果：

servlet文件上传及下载

下载：

package ni.jun.yang.servlet;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@WebServlet("/DownServlet")

public class downServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1.获取要下载的文件的绝对路径

        String realPath = this.getServletContext().getRealPath("111.txt");

        System.out.println(realPath);

        //2.获取要下载的文件名

        String fileName = realPath.substring(realPath.lastIndexOf(File.separator)+1);

        String userAgent = request.getHeader("User-Agent");

        //针对IE或者以IE为内核的浏览器：

        if (userAgent.contains("MSIE")||userAgent.contains("Trident")) {

            fileName = java.net.URLEncoder.encode(fileName, "UTF-8");

        } else {

        //非IE浏览器的处理：

            fileName = new String(fileName.getBytes("UTF-8"),"ISO-8859-1");

        }

        //3.设置content-disposition响应头控制浏览器以下载的方式打开文件

        response.setHeader("content-disposition","attachment;filename="+fileName);

        //4.获取要下载的文件输入流

        InputStream in = new FileInputStream(realPath);

        int len = 0;

        //5.创建书缓冲区

        byte[] buffer = new byte[1024];

        //6.通过response对象获取OutputStream输出流对象

        OutputStream os = response.getOutputStream();

        //7.将FileInputStream流对象写入到buffer缓冲区

        while((len=in.read(buffer))>0){

            os.write(buffer,0,len);

        }

        //8.关闭流

        in.close();

        os.close();

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doGet(request, response);

    }

}

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