package mypack;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
public class DownloadServlet extends HttpServlet { 
    public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException { 
        OutputStream out; //輸出響應正文的輸出流 
        InputStream in; //讀取本地文件的輸入流 //獲得filename請求參數 
        String filename=request.getParameter("filename"); 
        if(filename==null){ 
            out=response.getOutputStream(); 
            out.write("Please input filename.".getBytes()); 
            out.close();
            return; 
        } //創建讀取本地文件的輸入流 
     in= getServletContext().getResourceAsStream("/store/"+filename);
     int length=in.available(); //設置響應正文的MIME類型 
    response.setContentType("application/force-download"); 
    response.setHeader("Content-Length",String.valueOf(length)); 
    response.setHeader("Content-Disposition", "attachment;filename=\""+filename +"\" ");/** 把本地文件中的數據發送給客戶 */ 
    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(); 
    }
}