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<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：



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