Android作爲客戶端，PC作爲服務端：實現網絡通信

此項目實現網絡通信，android手機客戶端去請求PC服務端，將PC上mysql中的數據顯示在手機上。

   PC服務端用JavaWeb寫了個servlet，android手機客戶端請求這個servlet，由servlet執行查詢數據，並返回給手機客戶端，服務器爲Tomcat。

  爲了更清楚的展示，咱們現在mysql建一個測試表test

 

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

插入幾條記錄，我們這裏插入漢字，遇到亂碼，我們可以去解決。

insert into test values('張三');
insert into test values('李四');
insert into test values('王五');

 

插入成功

 

閒話少說，直接上代碼：

 

 

PC服務端

  我用MyEclipse建立了一個JavaWeb項目，這個項目中主要由一個數據查詢類DBManager.java和一個servlet（loadMessage.java）組成

 

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");// 這句可要可不要，以你不出現亂碼爲準
            //也可不用轉化，直接寫成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手機客戶端代碼：

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);
        // 查詢返回結果
        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 {
    // 基礎URL
    // 獲得Get請求對象request
    public static HttpGet getHttpGet(String url){
        HttpGet request = new HttpGet(url);
         return request;
    }
    // 獲得Post請求對象request
    public static HttpPost getHttpPost(String url){
         HttpPost request = new HttpPost(url);
         return request;
    }
    // 根據請求獲得響應對象response
    public static HttpResponse getHttpResponse(HttpGet request) throws ClientProtocolException, IOException{
        HttpResponse response = new DefaultHttpClient().execute(request);
        return response;
    }
    // 根據請求獲得響應對象response
    public static HttpResponse getHttpResponse(HttpPost request) throws ClientProtocolException, IOException{
        HttpResponse response = new DefaultHttpClient().execute(request);
        return response;
    }

    // 發送Post請求，獲得響應查詢結果
    public static String queryStringForPost(String url){
        // 根據url獲得HttpPost對象
        HttpPost request = HttpUtil.getHttpPost(url);
        String result = null;
        try {
            // 獲得響應對象
            HttpResponse response = HttpUtil.getHttpResponse(request);
            // 判斷是否請求成功
            if(response.getStatusLine().getStatusCode()==200){
                // 獲得響應
                result = EntityUtils.toString(response.getEntity());
                 //result=new  String(result.getBytes("8859_1"),"GB2312");  這句可要可不要，以你不出現亂碼爲準


                return result;
            }
        } catch (ClientProtocolException e) {
            e.printStackTrace();
            result = "網絡異常！";
            return result;
        } catch (IOException e) {
            e.printStackTrace();
            result = "網絡異常！";
            return result;
        }
        return null;
    }
}

 

當然還得在AndroidManifest.xml中加入網絡訪問權限：

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

 

需要注意的寫服務器的主機號時，千萬不能寫localhost或者127.0.0.1，因爲Android模擬器雖然和服務端程序在同一臺電腦上，但兩個畢竟是獨立的系統，我們可以用10.0.2.2去訪問本機。

 

運行結果：

 

這是在模擬器上運行，有的同學有這樣的想法，把ip改成自己電腦真實的Ip，把客戶端拿到真機上去實驗，但運行後會發現會顯示“網絡異常”，不能訪問。這裏涉及到了網絡方面的問題，其實也非常簡單。下篇博客將會詳細的講解，去解決這個問題。

 

 

 補充：上傳兩個項目，不禁可以訪問mysql，也可以訪問Access數據庫。

下載地址：http://download.csdn.net/detail/pzhtpf/4388157