Java WEB 实现下载功能

下面的demo实现从服务器上面下载文件的功能:

package mypack;

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 DownloadServlet extends HttpServlet{

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
            OutputStream out;
            InputStream in;
            
            String filename=request.getParameter("filename");
            if(filename==null){
                out=response.getOutputStream();
                out.write("Please input filename.".getBytes());
                out.close();
                return ;
            }
            
            in=getServletContext().getResourceAsStream("/store/"+filename);
            int length=in.available();
            
            response.setContentType("application/force=download");
            response.setHeader("Content-Length", String.valueOf(length));
            response.setHeader("Content-Disposition", "attachment;filename=\""
                    +filename+"\"");
            
            out=response.getOutputStream();
            int bytesRead=0;
            byte[] buffer=new byte[512];
            while((bytesRead=in.read(buffer))!=-1){
                out.write(buffer, 0, bytesRead);
            }
            
            in.close();
            out.close();
            
    }

    
    
}

然后再web.xml中配置:

<servlet>
        <servlet-name>DownloadServlet</servlet-name>
        <servlet-class>mypack.DownloadServlet</servlet-class>
    </servlet>
    
    <servlet-mapping>
        <servlet-name>DownloadServlet</servlet-name>
        <url-pattern>/download</url-pattern>
    </servlet-mapping>

 

下载的文件放在服务器helloapp/store下面,如果没有,则自行新建.

在浏览器中输入:

http://localhost:8080/helloapp/download?filename=Update.rar

 

浏览器则会提示下载.