java文件下载

1. import java.io.FileInputStream;
   import java.io.IOException;
   import java.io.InputStream;
   import java.io.OutputStream;
   import javax.servlet.ServletContext;
   import javax.servlet.ServletException;
   import javax.servlet.http.HttpServlet;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   
   
   public class HelpWord extends HttpServlet
   {
     private static final long serialVersionUID = 1L;
   
   
     protected void doGet(HttpServletRequest request, HttpServletResponse response)
     {
       InputStream is = null;
       OutputStream os = null;
       try {
         String fileName = request.getParameter("fileName");//获取请求传递文件名
   
         response.setContentType(getServletContext().getMimeType(fileName));
   
         response.setHeader("Content-Disposition", "attachment;filename=" + fileName);
         String filePath = getServletContext().getRealPath("/download/" + fileName);
         is = new FileInputStream(filePath);
         os = response.getOutputStream();
         int b = 0;
         while ((b = is.read()) != -1)
           os.write(b);
       }
       catch (Exception e) {
       }
       finally {
         try {
           os.close();
           is.close();
         }
         catch (Exception e2)
         {
         }
       }
     }
   
   
     protected void doPost(HttpServletRequest request, HttpServletResponse response)
       throws ServletException, IOException
     {
       doGet(request, response);
     }
   }