Android客户端和服务器端数据交互的第一种方法

        网上有很多例子来演示Android客户端和服务器端数据如何实现交互不过这些例子大多比较繁杂，对于初学者来说这是不利的，现在介绍几种代码简单、逻辑清晰的交互例子，本篇博客介绍第一种：

        一、服务器端：

        代码1：添加名为“AndroidServerServlet.java”的文件

package com.ghj.packageofservlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class AndroidServerServlet extends HttpServlet {

	private static final long serialVersionUID = 6792396567928634227L;

	public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
		response.setContentType("text/plain; charset=UTF-8");
		request.setCharacterEncoding("UTF-8");
		System.err.println(request.getParameter("clientData"));
		PrintWriter printWriter = response.getWriter();
		printWriter.print("您好Android客户端！");
		printWriter.flush();
		printWriter.close();
	}
}

        代码2：修改名为“web.xml”的文件

	
		AndroidServerServlet
		com.ghj.packageofservlet.AndroidServerServlet
	

	
		AndroidServerServlet
		/AndroidServerServlet
	

        二、Android手机客户端：

        代码1：添加名为“AndroidClientActivity.java”的文件

package com.example.androidclient;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;

import android.app.Activity;
import android.os.Bundle;
import android.os.StrictMode;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class AndroidClientActivity extends Activity {
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.android_client);
		
		if (android.os.Build.VERSION.SDK_INT > 9) {
		    StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
		    StrictMode.setThreadPolicy(policy);
		}
		
		Button sendButton = (Button) findViewById(R.id.send_button);
		sendButton.setOnClickListener(new OnClickListener(){
			@Override
			public void onClick(View v) {
				HttpPost httpRequest = new HttpPost("http://172.16.99.207:8080/AndroidServer/AndroidServerServlet");
	    		List params = new ArrayList();
	    		params.add(new BasicNameValuePair("clientData", "您好服务器端！"));
	    		try {
	    			httpRequest.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));//设置请求参数项
	                HttpClient httpClient = new DefaultHttpClient();
	                HttpResponse httpResponse = httpClient.execute(httpRequest);//执行请求返回响应
	                if(httpResponse.getStatusLine().getStatusCode() == 200){//判断是否请求成功
	                	Toast.makeText(AndroidClientActivity.this, EntityUtils.toString(httpResponse.getEntity()), Toast.LENGTH_LONG).show();
	                }else{
	                	Toast.makeText(AndroidClientActivity.this, "没有获取到Android服务器端的响应！", Toast.LENGTH_LONG).show();
	                }
	            } catch (ClientProtocolException e) {
	            	e.printStackTrace();
	    		} catch (UnsupportedEncodingException e) {
	    			e.printStackTrace();
	    		} catch (IOException e) {
	    			e.printStackTrace();
	    		}
			}
		});
	}
}

        注意：请注意“AndroidClientActivity.java”文件中34、35、36和37这4行代码——如果没有这几行代码，则会出现android.os.NetworkOnMainThreadException异常，关于该异常请参见另一篇名为《 android.os.NetworkOnMainThreadException异常》博客

        代码2：添加名为“android_client.xml”的文件

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