Android作为客户端，PC作为服务端：实现网络通信

此项目实现网络通信，android手机客户端去请求PC服务端，将PC上mysql中的数据显示在手机上。

   PC服务端用JavaWeb写了个servlet，android手机客户端请求这个servlet，由servlet执行查询数据，并返回给手机客户端，服务器为Tomcat。

  为了更清楚的展示，咱们现在mysql建一个测试表test

 

 create table test(
 name varchar(20) primary key
 );

插入几条记录，我们这里插入汉字，遇到乱码，我们可以去解决。

 insert into test values('张三');
 insert into test values('李四');
 insert into test values('王五');

 

插入成功

 

闲话少说，直接上代码：

 

 

PC服务端

  我用MyEclipse建立了一个JavaWeb项目，这个项目中主要由一个数据查询类DBManager.java和一个servlet（loadMessage.java）组成

 

DBManager.java

 package com.njue.DBManager;

 import java.awt.List;
 import java.sql.*;
 import java.util.ArrayList;

 import org.omg.CORBA.Object;

 public class DBManager {
     ;
     String userName="root";
     String password="123456";
     Connection conn=null;
     Statement stmt=null;
     String url="jdbc:mysql://localhost:3306/mysql";
     ArrayList list=new ArrayList();
     String sql;
 public DBManager(){
     sql="select * from test;";
     try {
         Class.forName("com.mysql.jdbc.Driver");
         conn=DriverManager.getConnection(url,userName,password);
         stmt=conn.createStatement();
         ResultSet rst=stmt.executeQuery(sql);
         while(rst.next()){
             //String name=new   String(rst.getString("name").getBytes("latin1"), "UTF-8");
             String name=new   String(rst.getString("name").getBytes("latin1"), "GB2312");// 这句可要可不要，以你不出现乱码为准
             //也可不用转化，直接写成String name=rst.getString("name");
             list.add(name);

         }
         rst.close();
     } catch (Exception e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     }
 }
 public ArrayList getList(){
     return list;
     }
 }

 

loadMessage.java

 package com.amaker.servlet;

 import java.awt.List;
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.util.ArrayList;

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

 import com.njue.DBManager.DBManager;

 public class loadMessage extends HttpServlet {
     public loadMessage() {
         super();
     }
     public void destroy() {
         super.destroy(); // Just puts "destroy" string in log
         // Put your code here
     }

     public void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
     //  request.setCharacterEncoding("UTF-8");
         response.setContentType("text/html; charset=UTF-8" );
         PrintWriter out = response.getWriter();
          String message="";
          DBManager db=new DBManager();
            ArrayList list=db.getList();
            for(int i=0;i
                message=message+list.get(i)+"\r\n";
            }
         out.print(message);
         out.flush();
         out.close();
     }
     public void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         doGet(request,response);

     }
     public void init() throws ServletException {
         // Put your code here
     }

 }

 

 

Android手机客户端代码：

AndroidClientActivity.java

 package com.njue.androidClient;
 import android.app.Activity;
 import android.os.Bundle;
 import android.widget.TextView;

 public class AndroidClientActivity extends Activity {
     /** Called when the activity is first created. */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);
         TextView tv=(TextView)findViewById(R.id.tv);
         // 查询返回结果
         String result = HttpUtil.queryStringForPost("http://10.0.2.2:8080/androidWeb/servlet/loadMessage");
         //String result = HttpUtil.queryStringForPost("http://122.88.34.123:8080/androidWeb/servlet/loadMessage");
         tv.setText(result);
     }
 }

 

HttpUtil.java

 package com.njue.androidClient;

 import java.io.IOException;

 import org.apache.http.HttpResponse;
 import org.apache.http.client.ClientProtocolException;
 import org.apache.http.client.methods.HttpGet;
 import org.apache.http.client.methods.HttpPost;
 import org.apache.http.impl.client.DefaultHttpClient;
 import org.apache.http.util.EntityUtils;

 public class HttpUtil {
     // 基础URL
     // 获得Get请求对象request
     public static HttpGet getHttpGet(String url){
         HttpGet request = new HttpGet(url);
          return request;
     }
     // 获得Post请求对象request
     public static HttpPost getHttpPost(String url){
          HttpPost request = new HttpPost(url);
          return request;
     }
     // 根据请求获得响应对象response
     public static HttpResponse getHttpResponse(HttpGet request) throws ClientProtocolException, IOException{
         HttpResponse response = new DefaultHttpClient().execute(request);
         return response;
     }
     // 根据请求获得响应对象response
     public static HttpResponse getHttpResponse(HttpPost request) throws ClientProtocolException, IOException{
         HttpResponse response = new DefaultHttpClient().execute(request);
         return response;
     }

     // 发送Post请求，获得响应查询结果
     public static String queryStringForPost(String url){
         // 根据url获得HttpPost对象
         HttpPost request = HttpUtil.getHttpPost(url);
         String result = null;
         try {
             // 获得响应对象
             HttpResponse response = HttpUtil.getHttpResponse(request);
             // 判断是否请求成功
             if(response.getStatusLine().getStatusCode()==200){
                 // 获得响应
                 result = EntityUtils.toString(response.getEntity());
                  //result=new  String(result.getBytes("8859_1"),"GB2312");  这句可要可不要，以你不出现乱码为准


                 return result;
             }
         } catch (ClientProtocolException e) {
             e.printStackTrace();
             result = "网络异常！";
             return result;
         } catch (IOException e) {
             e.printStackTrace();
             result = "网络异常！";
             return result;
         }
         return null;
     }
 }

 

当然还得在AndroidManifest.xml中加入网络访问权限：

 

需要注意的写服务器的主机号时，千万不能写localhost或者127.0.0.1，因为Android模拟器虽然和服务端程序在同一台电脑上，但两个毕竟是独立的系统，我们可以用10.0.2.2去访问本机。

 

运行结果：

 

这是在模拟器上运行，有的同学有这样的想法，把ip改成自己电脑真实的Ip，把客户端拿到真机上去实验，但运行后会发现会显示“网络异常”，不能访问。这里涉及到了网络方面的问题，其实也非常简单。下篇博客将会详细的讲解，去解决这个问题。

 

 

 补充：上传两个项目，不仅可以访问mysql，也可以访问Access数据库。

下载地址：http://download.csdn.net/detail/pzhtpf/4388157