//post和get方式登录的区别 (1)**************路径不同 
					
					String path = "http://192.168.22.73:8080/web/LoginServlet";
					try {
						URL url = new URL(path);
						//打开一个url连接 
						HttpURLConnection conn = (HttpURLConnection) url.openConnection();
						//设置conn 的参数 
						conn.setRequestMethod("POST");
						conn.setConnectTimeout(5000);
						//获取服务器返回的状态码
						
						//post和get方式登录的区别 (2)**************要设置头信息 Content-Type  Content-Length
						String data="username="+URLEncoder.encode(name, "utf-8")+"&password="+URLEncoder.encode(pwd, "utf-8")+"";
						conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
						conn.setRequestProperty("Content-Length", data.getBytes().length+"");
						
						//post和get方式登录的区别 (3)************** 以流的形式把数据写给服务器
						conn.setDoOutput(true); //设置一个标记 允许输出
						conn.getOutputStream().write(data.getBytes()); 
						
						int code = conn.getResponseCode();
						
						if (code == 200) { //200 请求服务器资源全部返回成功     //206 请求部分服务器资源返回成功   
							InputStream inputStream = conn.getInputStream(); //获取服务器返回的数据 
							//就是服务器返回数据  ---
							String content = StreamTools.readStream(inputStream); 
							
							//toast 也不可以在子线程更新 
						
							showToast(content);
						}
注：URLEncoder.encode（）This class is used to encode a string using the format required by application/x-www-form-urlencoded MIME content type. 

	
	//显示一个toast
	public void showToast(final String content){
		runOnUiThread(new Runnable() {
			
			@Override
			public void run() {
			
				Toast.makeText(getApplicationContext(), content, 1).show();
			}
		});
	}
	
	
}

public class StreamTools {
	/**
	 * 读取流
	 * @param in
	 * @return
	 * @throws IOException 
	 */
	public static String readStream(InputStream in) throws IOException{
		//定义一个内存输入流    bos 流不用关闭  关闭无效
		ByteArrayOutputStream bos = new ByteArrayOutputStream();
	    int  len  = -1;
	    byte buffer[] = new byte[1024];
	    while((len = in.read(buffer))!=-1){
	    	bos.write(buffer, 0, len);
	    };
	    in.close();
		return new String(bos.toByteArray(),"gbk");
		
	}
	
}