网上有非常多样例来演示Android客户端和server端数据怎样实现交互只是这些样例大多比較繁杂，对于刚開始学习的人来说这是不利的。如今介绍几种代码简单、逻辑清晰的交互样例，本篇博客介绍第一种：

        一、server端：

        代码1：加入名为“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：改动名为“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：加入名为“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<NameValuePair> params = new ArrayList<NameValuePair>();
          params.add(new BasicNameValuePair("clientData", "您好server端！"));
          try {
            httpRequest.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));//设置请求參数项
                  HttpClient httpClient = new DefaultHttpClient();
                  HttpResponse httpResponse = httpClient.execute(httpRequest);//运行请求返回响应
                  if(httpResponse.getStatusLine().getStatusCode() == 200){//推断是否请求成功
                    Toast.makeText(AndroidClientActivity.this, EntityUtils.toString(httpResponse.getEntity()), Toast.LENGTH_LONG).show();
                  }else{
                    Toast.makeText(AndroidClientActivity.this, "没有获取到Androidserver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”文件里34、35、36和37这4行代码——假设没有这几行代码，则会出现android.os.NetworkOnMainThreadException异常,常代码2：加入名为“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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