Android客户端和服务器端数据交互的第三种方法

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，本篇博客介绍第三种：

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

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

	<servlet>
		<servlet-name>AndroidServerServlet</servlet-name>
		<servlet-class>com.ghj.packageofservlet.AndroidServerServlet</servlet-class>
	</servlet>

	<servlet-mapping>
		<servlet-name>AndroidServerServlet</servlet-name>
		<url-pattern>/AndroidServerServlet</url-pattern>
	</servlet-mapping>
</web-app>

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.Looper;
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);

		Button sendButton = (Button) findViewById(R.id.send_button);
		sendButton.setOnClickListener(new OnClickListener(){
			@Override
			public void onClick(View v) {
				new Thread(new Runnable(){
				    @Override
				    public void run() {
				    	Looper.prepare();
				    	HttpPost httpRequest = new HttpPost("http://172.16.99.207:8080/AndroidServer/AndroidServerServlet");
			    		List<NameValuePair> params = new ArrayList<NameValuePair>();
			    		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();
			    		}
			    		Looper.loop();
				    }
				}).start();
			}
		});
	}
}

注意：上面代码第41行和第61行不可缺少，否则会出现java.lang.RuntimeException: Can‘t create handler inside thread that has not called Looper.prepare()异常，关于该异常请参见另一篇名为《Android中的Can‘t create handler inside thread that has not called Looper.prepare()异常》博客。

代码2：添加名为“android_client.xml”的文件

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

   <Button
       android:id="@+id/send_button"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_centerHorizontal="true"
       android:layout_centerVertical="true"
       android:text="@string/hello_server" />

</RelativeLayout>

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