Android与WEB服务器交互时，如何保证在同一个会话Session中通信

package com.lxbang.demo;

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import android.net.UrlQuerySanitizer;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
import android.view.View;

public class MainActivity extends Activity {

private String token = null;

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

Handler handler = new Handler() {

public void handleMessage(Message msg) {

token = (String) msg.obj;
Log.d("ddd", "token----" + token);
};

};

public void onBtnClick(View view) {

if (R.id.button1 == view.getId()) {
new Thread(new Runnable() {

@Override
public void run() {
// TODO Auto-generated method stub

try {
URL url = new URL(
"http://172.17.129.151:8080/meten_lxb/demoAction");
HttpURLConnection connection = (HttpURLConnection) url
.openConnection();
// 取得sessionid.
String cookieval = connection
.getHeaderField("set-cookie");
String sessionid = null;
if (cookieval != null) {
sessionid = cookieval.substring(0,
cookieval.indexOf(";"));
}
Log.d("ddd", sessionid + "----");
InputStream is = connection.getInputStream();
Message msg = new Message();
msg.obj = sessionid;
handler.sendMessage(msg);

} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}
}).start();

}
if (R.id.button2 == view.getId()) {
new Thread(new Runnable() {

@Override
public void run() {
try {
URL url = new URL(
"http://172.17.129.151:8080/meten_lxb/demoAction");
HttpURLConnection connection = (HttpURLConnection) url
.openConnection();
if (token != null) {
connection.setRequestProperty("cookie", token);
}
InputStream is = connection.getInputStream();

} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}
}).start();
}
}
}