Android - 向服务器发送数据(GET).

　　在此,使用HTTP协议,通过GET请求,向服务器发送请求,这种方式适合于数据量小,数据安全性要求不高的情况下.

一,服务器端,使用Servlet.

　　在服务器端,定义一个HttpServlet的子类,以及一个Filter的子类(用于统一编码,防止出现乱码).

package spt.servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * type 'http://localhost:8080/ReceiveAndroid/ServletForGETMethod?name=juk&pwd=lis'
 * for the browser.
 */
@WebServlet("/ServletForGETMethod")
public class ServletForGETMethod extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public ServletForGETMethod() {
		super();
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		String name = request.getParameter("name");
		String pwd = request.getParameter("pwd");
		System.out.println("name:" + name + "   pwd:" + pwd);

	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
	}

}

package spt.servlet.filter;

import java.io.IOException;
import java.io.UnsupportedEncodingException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

//filter all servlets.
@WebFilter("/*")
public class EncodingFilter  implements Filter {

	public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
		HttpServletRequest httpReq = (HttpServletRequest) servletRequest;
		if ("GET".equals(httpReq.getMethod()))
			filterChain.doFilter(new HttpServletRequestEncodingWrapper(httpReq), servletResponse);
		else {
			httpReq.setCharacterEncoding("utf-8");
			filterChain.doFilter(httpReq, servletResponse);
		}
	}

	public void init(FilterConfig filterConfig) throws ServletException {
		// TODO Auto-generated method stub

	}

	/**inner class dealing for 'GET' method.
	 * @author Administrator
	 *2015-1-27
	 */
	private class HttpServletRequestEncodingWrapper extends HttpServletRequestWrapper {

		public HttpServletRequestEncodingWrapper(HttpServletRequest request) {
			super(request);
		}

		@Override
		public String getParameter(String name) {
			//encode with 'iso', and than decode with 'utf'.
			String val = super.getRequest().getParameter(name);
			if (null != val) {
				try {
					return new String(val.getBytes("iso8859-1"), "utf-8");
				} catch (UnsupportedEncodingException e) {
					e.printStackTrace();
				}
			}
			return super.getParameter(name);
		}
	}

	public void destroy() {
		// TODO Auto-generated method stub

	}

}

在主机(服务器)上,往浏览器中输入'http://localhost:8080/ReceiveAndroid/ServletForGETMethod?name=juk&pwd=lis', 若在控制台打印需要的结果,则表示服务器端的Servlet已经编写好.

二,Android的业务逻辑层类,主要是将业务逻辑独立于Android的Activity.

package spt.http.get.assist;

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import android.os.Handler;

/**用户向服务器端发送数据的类.
 * @author Administrator
 *
 */
public class SendDataToServer {
	private static final int TIME_OUT = 10000; // 超时时间.
	// 连接服务器的url.
	private static final String URL = "http://192.168.1.101:8080/ReceiveAndroid/ServletForGETMethod";
	// 标识是否连接到服务器成功.
	public static final int SEND_SUCCESS = 1;
	public static final int SEND_FAIL = 0;

	private Handler handler = null;

	public SendDataToServer(Handler handler) {
		this.handler = handler;
	}

	/**
	 * 往服务器发送数据.
	 *
	 * @param name
	 * @param pwd
	 */
	public void send(String name, String pwd) {
		// 这里params要传递到另外一个方法,加final为了防止被修改.
		final Map<String, String> params = new HashMap<String, String>();
		params.put("name", name);
		params.put("pwd", pwd);

		// 启动新的线程连接服务器.
		new Thread(new Runnable() {

			@Override
			public void run() {
				// 使用get请求连接.
				try {
					if (getSend(params, URL, "utf-8"))
						handler.sendEmptyMessage(SEND_SUCCESS);
					else
						handler.sendEmptyMessage(SEND_FAIL);
				} catch (MalformedURLException e) {
					e.printStackTrace();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}).start();
	}

	/**发送get请求的方法.
	 * @param params 请求参数的键-值对.
	 * @param url
	 * @param encoding 使用指定编码对参数值进行编码.
	 * @return
	 * @throws MalformedURLException
	 * @throws IOException
	 */
	private boolean getSend(Map<String, String> params, String url,
			String encoding) throws MalformedURLException, IOException {
		StringBuilder sb = new StringBuilder();
		// 向url中添加参数.
		sb.append(url).append("?");
		for (Entry<String, String> param : params.entrySet()) {
			sb.append(param.getKey()).append("=")
					.append(URLEncoder.encode(param.getValue(), encoding))
					.append("&");
		}
		if (params.size() > 0)
			sb.deleteCharAt(sb.length() - 1); // 去掉末尾的'&'.
		HttpURLConnection conn = (HttpURLConnection) new URL(sb.toString())
				.openConnection();
		conn.setConnectTimeout(TIME_OUT);
		conn.setRequestMethod("GET"); // GET是大小写敏感的.

		return conn.getResponseCode() == 200; // 等于200表示发送成功.
	}
}

三:Activity类:

package spt.http.get.activity;

import java.lang.ref.WeakReference;

import spt.http.get.assist.SendDataToServer;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {
	//view.
	private EditText edt_name = null;
	private EditText edt_pwd = null;
	private Button btn_ok = null;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		initView();
		initListener();
	}

	/**
	 * 初始化View.
	 */
	private void initView() {
		edt_name = (EditText)findViewById(R.id.edt_name);
		edt_pwd = (EditText)findViewById(R.id.edt_pwd);
		btn_ok = (Button)findViewById(R.id.btn_ok);

		//test:
		edt_name.setText("你好");
		edt_pwd.setText("abc");
	}

	/**使用静态内部类,解决'This Handler class should be static or leaks might occur',以免造成内存泄露.
	 * @author Administrator
	 *
	 */
	private static class StatusHandler extends Handler {
		WeakReference<MainActivity>  iMainActivity = null;

		public StatusHandler(MainActivity mainActivity) {
			iMainActivity = new WeakReference<MainActivity>(mainActivity);
		}

		@Override
		public void handleMessage(Message msg) {
			switch (msg.what) {
			case SendDataToServer.SEND_SUCCESS:
				//有iMainActivity.get()和iMainActivity.getClass().
				Toast.makeText(iMainActivity.get(), "发送成功", Toast.LENGTH_SHORT).show();
				break;
			case SendDataToServer.SEND_FAIL:
				Toast.makeText(iMainActivity.get(), "发送失败", Toast.LENGTH_SHORT).show();
				break;
			default:
				throw new RuntimeException("未知的发送结果!");
			}
		}
	}

	/**
	 * 处理发送是否成功的状态的Handler.
	 */
	private final  Handler handler = new StatusHandler(this);

	/**
	 * 初始化监听器.
	 */
	private void initListener() {
		btn_ok.setOnClickListener(new Button.OnClickListener() {

			@Override
			public void onClick(View v) {
				String name = edt_name.getText().toString();
				String pwd = edt_pwd.getText().toString();
				if(name.isEmpty() || pwd.isEmpty()) {
					Toast.makeText(MainActivity.this, "用户名和密码不能为空", Toast.LENGTH_SHORT).show();
					return;
				}
				new SendDataToServer(handler).send(name, pwd);
			}
		});
	}
}

稍微留意的是,Activity类中的Handler的子类定义为静态类,并保存对Activity的弱引用,防止内存泄露.简略解释在我的博文 Android - This Handler class should be static or leaks might occur. 中.

四, 添加必要权限

　　在AndroidManifest.xml中,添加

<uses-permission android:name="android.permission.INTERNET" />

以对网络的访问.