上傳圖片，不成功??？沒反應(yīng)

URL httpUrl=new URL(url);
???HttpURLConnection conn=(HttpURLConnection)httpUrl.openConnection();
???conn.setRequestMethod("POST");
???conn.setDoOutput(true);
???conn.setDoInput(true);//請(qǐng)求屬性
???conn.setRequestProperty("Content-Type","multipart/form-data;boundary="+boundary);
???DataOutputStream out=new DataOutputStream(conn.getOutputStream());
???out.writeBytes(prefix+boundary+end);
???out.writeBytes("Content-Disposition:form-data;"+"name=\"upload\";filename=\""+"Sky.jpg"+"\""+end);
???out.writeBytes(end);//回車換行符
???FileInputStream fileInputStream=new FileInputStream(new File(fileName));
???byte[] b=new byte[1024*4];
???int len;
???while((len=fileInputStream.read(b))!=-1){
????out.write(b,0,len);
???}
???out.writeBytes(end);
???out.writeBytes(prefix+boundary+prefix+end);//最后結(jié)束行
???out.flush();
???