`

文件下载

    博客分类：
  • jsp
JavaServlet.netJSPHTML 
阅读更多
这里只是一个最简单的例子：

Servlet: 
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Download extends HttpServlet {

	private static final long serialVersionUID = -9010014940000834313L;

	public Download() {
		super();
	}

	public void destroy() {
	}

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

		doPost(request, response);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		/*
		 * 下列代码 实现本地文件的下载功能:提供给他人下载
		 */
		String filePath = request.getSession().getServletContext().getRealPath( "/")+"usr/";
		//request.getSession().getServletContext().getRealPath( "/")项目的根路径
		System.out.println(filePath);
		//String fileName = "Operator.doc".toString();  //文件的默认保存名
		String fileName = request.getParameter("fileName");
		System.out.println(fileName);
		
		//设置输出的格式
		response.reset();
		response.setContentType( "application/text;charset=GB2312 "); 
		response.addHeader("Content-Disposition","attachment; filename=\"" + fileName + "\"");
		
		//防止出现fileName为null出异常
		if (fileName!=null) {
			//读到流中
			InputStream inStream=new FileInputStream(filePath+fileName);
			//循环取出流中的数据
			byte[] b = new byte[100];
		    int len;
		    OutputStream out=response.getOutputStream();
		    while((len=inStream.read(b)) >0){
		    	out.write(b,0,len); 
		    }
		    inStream.close();
		    out.close();
		}
		
	}

	public void init() throws ServletException {
	}

}


Jsp: 
<%@ page language="java" pageEncoding="gbk"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    
    <title>downloadFile</title>

  </head>
  
  <body>
    <center>
    <form action="download" method="post">
    <table>
    <tr>
    <td><input type="hidden"name="fileName" value="a.txt"/>a.txt</td><td><input type="submit" value="下载"/></td>
    </tr>
    </table>
    </form>
    </center>
  </body>
</html>


======================================
从网络下载到本地： 
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;

public class DownloadFile {

	public static void main(String[] args) {
		try{
		/*
		 * 下列代码 实现网络文件的下载功能:从网络上下载文件到本地
		 */
		int bytesum=0;

		int byteread=0;

		URL url = new URL("http://qsrock.iteye.com/admin/blogs/156364");

		 URLConnection conn = url.openConnection();

		 InputStream inStream = conn.getInputStream();

		 FileOutputStream fs=new FileOutputStream( "/usr/a.html");

		  byte[]  buffer =new  byte[1204];

		   int length;

		    while ((byteread=inStream.read(buffer))!=-1){

		       bytesum+=byteread;

		       System.out.println(bytesum);

		       fs.write(buffer,0,byteread);
		     }

		}catch (Exception e) {
			e.printStackTrace();
		}
	}

}

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