Android作为客户端，PC作为服务端：实现网络通信

悠悠 2021-07-04 23:15 582阅读 0赞

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

![1339727809_9516.PNG][]

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<String> list=new ArrayList<String>();
    	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<String> 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<String> list=db.getList();
    	       for(int i=0;i<list.size();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：

<uses-permission android:name="android.permission.INTERNET"></uses-permission>

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：

![1339728189_6419.PNG][]

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，不禁可以访问mysql，也可以访问Access数据库。**

**下载地址：**[**http://download.csdn.net/detail/pzhtpf/4388157**][http_download.csdn.net_detail_pzhtpf_4388157]

** **

[1339727809_9516.PNG]: https://img-my.csdn.net/uploads/201206/15/1339727809_9516.PNG
[1339728189_6419.PNG]: https://img-my.csdn.net/uploads/201206/15/1339728189_6419.PNG
[http_download.csdn.net_detail_pzhtpf_4388157]: http://download.csdn.net/detail/pzhtpf/4388157