文件下载 （本域 及 跨域文件下载）

//文件下载 （本域 及 跨域文件下载）
public void downAnnex(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, int systemMark ,String annexPath) throws Exception {

response.setCharacterEncoding("utf-8");
BufferedInputStream bis = null;
BufferedOutputStream bos = null;
OutputStream fos = null;
InputStream fis = null;
String filepath = "";
        String kidRootPath = "http://192.168.18.55:8888/kid/";//目标域的 域名

        if(systemMark == 1){//本服务哭器下载文件
        filepath = servlet.getServletContext().getRealPath("/" + annexPath);
        File uploadFile = new File(filepath);
            fis = new FileInputStream(uploadFile);
            bis = new BufferedInputStream(fis);
            fos = response.getOutputStream();
            bos = new BufferedOutputStream(fos);
          
            response.setHeader("Content-disposition","attachment;filename=" +URLEncoder.encode(annexPath.substring(annexPath.lastIndexOf("/")+1), "utf-8"));
            int bytesRead = 0;
           
            byte[] buffer = new byte[8192];
            while ((bytesRead = bis.read(buffer, 0, 8192)) != -1) {
                bos.write(buffer, 0, bytesRead);
            }
            bos.flush();
            fis.close();
            bis.close();
            fos.close();
            bos.close();

        }else{//跨域下载文件
        filepath = kidRootPath + annexPath;
        HttpURLConnection huc = (HttpURLConnection) new URL(filepath).openConnection();  

    // 设置连接属性  
    huc.setDoOutput(true);  
    huc.setRequestMethod("POST");  
    huc.setUseCaches(false);  
    huc.setInstanceFollowRedirects(true);  
    huc.setRequestProperty("Content-Type","application/x-www-form-urlencoded");  
    huc.connect();  

    // 往目标servlet中提供参数  
    OutputStream targetOS = huc.getOutputStream();  
    targetOS.write(filepath.getBytes());  
    targetOS.flush();  
    targetOS.close();  
   
      
    response.setContentType(huc.getContentType());  
    /*response.setHeader("Cache-Control", huc.getHeaderField("Cache-Control"));  
    response.setHeader("Pragma", huc.getHeaderField("Pragma"));  
    response.setHeader("Expires", huc.getHeaderField("Expires"));*/  
    response.setHeader("Content-disposition","attachment;filename=" +URLEncoder.encode(annexPath.substring(annexPath.lastIndexOf("/")+1), "utf-8"));
    OutputStream os = response.getOutputStream();  
   
    // 将目标servlet的输入流直接往页面输出  
    InputStream targetIS = huc.getInputStream();  
    int r;  
    while ((r = targetIS.read()) != -1) {  
    os.write(r);  
    }  
    targetIS.close();  
    os.flush();  
    os.close();  
   
    huc.disconnect();
        }  
}