文件下载

使用代码下载

package cn.servlet;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLEncoder;

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

public class DownServlet extends HttpServlet {
    @Override
    public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.err.println("判断用户的积分信息.....");
        //获取真实的文件
        String path = getServletContext().getRealPath("/files/cos.jar");
        //获取这个文件的io
        InputStream in = 
                new FileInputStream(path);
        //设置响应的头信息
        //如果希望将下载的文件修改成中文名，则必须要对中文名称进行编码
        String name = "下载的文件.jar";
        name = URLEncoder.encode(name,"UTF-8");
        resp.setHeader("Content-Disposition","attachment;filename="+name);
        resp.setContentType("application/force-download");
        
        byte[] bs = new byte[1024];
        OutputStream out = 
                resp.getOutputStream();
        int len = 0;
        while((len=in.read(bs))!=-1){
            out.write(bs,0,len);
        }
        in.close();
        out.close();
    }
}

<br>
    <a href="<c:url value='/files/cos.jar'/>">下载</a>
    <br>
    <a href="<c:url value='/down'/>">Download</a>

自己使用urlconnection实现下载

package cn.client;

import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
public class Client {
    public static void main(String[] args) throws Exception {
        //1:声明url地址
        URL url = new URL("http://localhost:8080/20151116/files/cos.jar");
        HttpURLConnection con = 
                (HttpURLConnection) url.openConnection();
        con.setRequestMethod("GET");
        con.setDoOutput(true);
        con.setDoInput(true);
        con.setConnectTimeout(3000);
        con.connect();
        
        //获取连接的状态
        int code = con.getResponseCode();
        if(code==200){
            InputStream in = 
                    con.getInputStream();
            byte[] bs = new byte[1024];
            int len = 0;
            OutputStream out = new FileOutputStream("d:/a/a.jar");
            while((len=in.read(bs))!=-1){
                out.write(bs, 0, len);
            }
            out.close();
            in.close();
        }
        con.disconnect();
    }
}