实现下载功能

import java.io.*;  
import java.text.*;  
import java.util.*;  
import javax.servlet.*;  
import javax.servlet.http.*;  
import java.net.*;  
/** 
*  实现下载功能 
*/  
public class DownLoad {  
        public void downLoad(HttpServletResponse response,   
String headName, String fileUrl) throws Exception{  
          
        Logger.log("begin download " + headName);          
        if (headName.endsWith(".jpg") || (headName.endsWith(".gif"))) {  
            //no need setting content type and header   
        } else if (headName.endsWith(".txt")) {  
            response.setContentType( "text;charset=GB2312");  
            response.setHeader("Content-disposition",    
                              "attachment; filename=" + headName );  
        } else {  
            response.setContentType( "application/doc;charset=GB2312");  
            response.setHeader("Content-disposition",    
                              "attachment; filename=" + headName );  
        }  
  
        String fileURL = fileUrl;  
        Logger.log(fileURL);  
        if(fileURL == null)  
            return;  
          
        try{  
            File file = new File(fileUrl);              
            FileInputStream bis = new FileInputStream(file);              
            OutputStream bos = response.getOutputStream();   
  
            byte[] buff = new byte[1024];  
            int readCount = 0;  
            int i = 0;  
            readCount = bis.read(buff);  
            while (readCount != -1){  
               bos.write(buff, 0, readCount);   
               readCount = bis.read(buff);  
            }  
            Logger.log("read finished!");  
            if (bis!=null)  
                bis.close();              
            if (bos!=null)  
                bos.close();  
  
        }catch(Exception e){  
           e.printStackTrace();             
           throw e;  
        }  
    }      
}

或者有下载

<%@ page contentType="text/html;charset=gbk"%>
<% 
 
String key=request.getParameter("key");
String fname=request.getParameter("fname");

response.setContentType("application/OCTET-STREAM;charset=GB2312");
response.setHeader("Content-Disposition", "attachment;filename="+Download.encodingFileName(fname));


UserData userdata = (UserData) session.getAttribute(Const.SID_USERDATA);
if(userdata!=null){
HashMap fmap=userdata.getFmap();
InputStream is=(InputStream)fmap.get(key);

//输出到指定的文件
//File path=new File("d:/temp/");
//if(!path.exists()){
// path.mkdir();
//}
//File file=new File("d:/temp/"+fname);
//if(!file.exists()){
// file.createNewFile();
//}
//FileOutputStream fi=null;
//BufferedOutputStream bos=null;
OutputStream bos=null;
BufferedInputStream bis=null;
try{
//fi=new FileOutputStream(file);
bis=new BufferedInputStream(is);
//bos=new BufferedOutputStream(fi);
bos=response.getOutputStream();
int c;
while ((c = bis.read()) != -1) {
bos.write(c);
bos.flush();
}
}catch(Exception ee){
ee.printStackTrace();
}finally{
bos.close();
bos=null;
bis.close();
bis=null;
//fi.close();
//fi=null;
}
//out.println("<script>alert('文件已经下载保存到D:/temp下，请查看');history.go(-1);</script>");
//return;
}
%>