Android面向HTTP协议发送post请求

/**
	 * 採用post请求的方式
	 * 
	 * @param username
	 * @param password
	 * @return null表示求得的路径有问题,text返回请求得到的数据
	 */
	public static String postRequest(String username, String password) {
		try {
			String path = "http://172.22.64.156:8080/0001AndroidWebService/LoginServlet";
			URL url = new URL(path);
			HttpURLConnection conn = (HttpURLConnection) url.openConnection();
			conn.setReadTimeout(500);
			conn.setRequestMethod("POST");
			// username=donghongyu&&password=123
			// 准备要传输的数据
			String data = "username=" + URLEncoder.encode(username)
					+ "&password=" + URLEncoder.encode(password);
			// 设置请求的内容的类型
			conn.setRequestProperty("Content-Type",
					"application/x-www-form-urlencoded");
			conn.setRequestProperty("Content-Length", data.length() + "");

			// 开启向server写入的权限
			conn.setDefaultUseCaches(true);
			// 获取http连接的输出流
			OutputStream os = conn.getOutputStream();
			// 向server写入数据
			os.write(data.getBytes());

			int code = conn.getResponseCode();
			if (code == 200) {
				// 请求成功
				InputStream is = conn.getInputStream();
				String text = StreamUtil.readStream(is);
				return text;
			} else {
				// 请求失败
				return null;
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		return null;
	}