/**
	 * 采用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 = http://www.mamicode.com/"username=" + URLEncoder.encode(username)>