Android网络开发中如何使用JSON进行网络通信---Android JSON数据通讯方法解析

Android网络开发中如何使用JSON进行网络通信---Android JSON数据通讯方法解析  

在开发客户端与服务端的应用当中，数据交换接口通常都是通过XML格式来进行数据交换的。近年来，随着AJAX技术的兴起，JSON作为一种轻量级的数据交换格式，以其易于阅读和编写的优点，也越来越多的被使用到各个项目中。在OPhone SDK中，也提供了JSON的类库方便对JSON格式的数据进行处理。本文将快速讲解 JSON 格式，并通过代码示例演示如何分别在客户端和服务器端进行 JSON 格式数据的处理。


1、服务端接口程序
      首先，我们创建一个名为User的JavaBean作为用户对象类，用来保存演示数据。


1.public   class  User {  
2.    private   int  id;  
3.    private  String name;  
4.    private  String email;  
5.    private  String gender;  
6.      
7.    public   int  getId() {  
8.        return  id;  
9.    }  
10.    public   void  setId( int  id) {  
11.        this .id = id;  
12.    }  
13.    public  String getName() {  
14.        return  name;  
15.    }  
16.    public   void  setName(String name) {  
17.        this .name = name;  
18.    }  
19.    public  String getEmail() {  
20.        return  email;  
21.    }  
22.    public   void  setEmail(String email) {  
23.        this .email = email;  
24.    }  
25.    public  String getGender() {  
26.        return  gender;  
27.    }  
28.    public   void  setGender(String gender) {  
29.        this .gender = gender;  
30.    }  
31.      
32.}  
public class User {
    private int id;
    private String name;
    private String email;
    private String gender;
    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    
}
      接下来，我们创建一个名为JSONDemoServlet的Servlet类来作为服务端的接口程序。在这个程序里，定义了一个List对象用来保存用户列表。


1.private  List<User> list;  
private List<User> list;        客户端程序访问服务器端接口时，接口通过prepareData方法为用户列表初始化数据，添加用户数据到List对象中。


1.private   void  prepareData(){  
2.        list = new  ArrayList<User>();  
3.        User bean1 = new  User();  
4.        bean1.setId(1001 );  
5.        bean1.setName("Tony" );  
6.        bean1.setEmail("[email protected]" );  
7.        bean1.setGender("male" );  
8.        list.add(bean1);  
9.        ……  
10.    }  
private void prepareData(){
        list = new ArrayList<User>();
        User bean1 = new User();
        bean1.setId(1001);
        bean1.setName("Tony");
        bean1.setEmail("[email protected]");
        bean1.setGender("male");
        list.add(bean1);
        ……
    }
      接着遍历用户列表，把列表中的每个Java用户对象转换为JSONObject对象，再加入到JSONArray中去。


1.JSONArray array =  new  JSONArray();  
2.    for (User bean:list){  
3.        //单个用户JSON对象    
4.        JSONObject obj = new  JSONObject();  
5.              
6.        try {  
7.            obj.put("id" , bean.getId());  
8.            obj.put("name" , bean.getName());  
9.            obj.put("email" , bean.getEmail());  
10.            obj.put("gender" , bean.getGender());  
11.        } catch  (Exception e) {}  
12.              
13.            array.put(obj);  
14.    }  
JSONArray array = new JSONArray();
    for(User bean:list){
        //单个用户JSON对象
        JSONObject obj = new JSONObject();
            
        try{
            obj.put("id", bean.getId());
            obj.put("name", bean.getName());
            obj.put("email", bean.getEmail());
            obj.put("gender", bean.getGender());
        } catch (Exception e) {}
            
            array.put(obj);
    }
       最后，通过 Servlet输出 JSON 时，需要设置正确的 MIME 类型和字符编码。假定服务器使用 UTF-8 编码，则可以使用以下代码输出编码后的 JSON 文本：


1.response.setContentType( "text/plain" );  
2.    response.setCharacterEncoding("UTF-8" );  
3.    PrintWriter out = response.getWriter();  
4.out.write(array.toString());  
5.    out.flush();  
6.    out.close();  
7.  
8.JSONDemoServlet.java的完整代码如下：  
9.import  java.io.IOException;  
10.import  java.io.PrintWriter;  
11.import  java.util.ArrayList;  
12.import  java.util.List;  
13.  
14.import  javax.servlet.ServletException;  
15.import  javax.servlet.http.HttpServlet;  
16.import  javax.servlet.http.HttpServletRequest;  
17.import  javax.servlet.http.HttpServletResponse;  
18.  
19.import  org.json.JSONArray;  
20.import  org.json.JSONObject;  
21.  
22.public   class  JSONDemoServlet  extends  HttpServlet{  
23.    private   static   final   long  serialVersionUID = -7368225680407826408L;  
24.    private  List<User> list;  
25.      
26.    /**  
27.     * 处理post方式提交的数据  
28.     */    
29.    public   void  doPost(HttpServletRequest request, HttpServletResponse response) throws  ServletException, IOException {  
30.        doGet(request,response);  
31.    }  
32.        /**  
33.        * 出来get方式提交的数据  
34.        */    
35.        public   void  doGet(HttpServletRequest request, HttpServletResponse response)  throws  ServletException, IOException {  
36.            response.setContentType("text/plain" );  
37.            response.setCharacterEncoding("UTF-8" );  
38.            PrintWriter out = response.getWriter();  
39.          
40.            //准备用户数据    
41.            prepareData();  
42.          
43.            //JSON数组    
44.            JSONArray array = new  JSONArray();  
45.            for (User bean:list){  
46.                //单个用户JSON对象    
47.                JSONObject obj = new  JSONObject();  
48.              
49.                try {  
50.                    obj.put("id" , bean.getId());  
51.                    obj.put("name" , bean.getName());  
52.                    obj.put("email" , bean.getEmail());  
53.                    obj.put("gender" , bean.getGender());  
54.                } catch  (Exception e) {}  
55.              
56.                    array.put(obj);  
57.            }  
58.          
59.            //输出    
60.            out.write(array.toString());  
61.            out.flush();  
62.            out.close();  
63.        }  
64.        private   void  prepareData(){  
65.            list = new  ArrayList<User>();  
66.            User bean1 = new  User();  
67.            bean1.setId(1001 );  
68.            bean1.setName("Tony" );  
69.            bean1.setEmail("[email protected]" );  
70.            bean1.setGender("male" );  
71.            list.add(bean1);  
72.          
73.            User bean2 = new  User();  
74.            bean2.setId(1002 );  
75.            bean2.setName("Jack" );  
76.            bean2.setEmail("[email protected]" );  
77.            bean2.setGender("male" );  
78.            list.add(bean2);  
79.          
80.            User bean3 = new  User();  
81.            bean3.setId(1003 );  
82.            bean3.setName("Marry" );  
83.            bean3.setEmail("[email protected]" );  
84.            bean3.setGender("female" );  
85.            list.add(bean3);  
86.          
87.            User bean4 = new  User();  
88.            bean4.setId(1004 );  
89.            bean4.setName("Linda" );  
90.            bean4.setEmail("[email protected]" );  
91.            bean4.setGender("female" );  
92.            list.add(bean4);  
93.        }  
94.}  
response.setContentType("text/plain");
    response.setCharacterEncoding("UTF-8");
    PrintWriter out = response.getWriter();
out.write(array.toString());
    out.flush();
    out.close();

JSONDemoServlet.java的完整代码如下：
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;

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

import org.json.JSONArray;
import org.json.JSONObject;

public class JSONDemoServlet extends HttpServlet{
    private static final long serialVersionUID = -7368225680407826408L;
    private List<User> list;
    
    /**
     * 处理post方式提交的数据
     */
    public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        doGet(request,response);
    }
        /**
         * 出来get方式提交的数据
         */
        public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            response.setContentType("text/plain");
            response.setCharacterEncoding("UTF-8");
            PrintWriter out = response.getWriter();
        
            //准备用户数据
            prepareData();
        
            //JSON数组
            JSONArray array = new JSONArray();
            for(User bean:list){
                //单个用户JSON对象
                JSONObject obj = new JSONObject();
            
                try{
                    obj.put("id", bean.getId());
                    obj.put("name", bean.getName());
                    obj.put("email", bean.getEmail());
                    obj.put("gender", bean.getGender());
                } catch (Exception e) {}
            
                    array.put(obj);
            }
        
            //输出
            out.write(array.toString());
            out.flush();
            out.close();
        }
        private void prepareData(){
            list = new ArrayList<User>();
            User bean1 = new User();
            bean1.setId(1001);
            bean1.setName("Tony");
            bean1.setEmail("[email protected]");
            bean1.setGender("male");
            list.add(bean1);
        
            User bean2 = new User();
            bean2.setId(1002);
            bean2.setName("Jack");
            bean2.setEmail("[email protected]");
            bean2.setGender("male");
            list.add(bean2);
        
            User bean3 = new User();
            bean3.setId(1003);
            bean3.setName("Marry");
            bean3.setEmail("[email protected]");
            bean3.setGender("female");
            list.add(bean3);
        
            User bean4 = new User();
            bean4.setId(1004);
            bean4.setName("Linda");
            bean4.setEmail("[email protected]");
            bean4.setGender("female");
            list.add(bean4);
        }
}
       把该Servlet部署到Tomcat下，在浏览器输入接口地址http://localhost:8080/article/JSONDemoServlet ，输出结果如下：
[{"id":1001,"email":"[email protected]","name":"Tony","gender":"male"},{"id":1002,"email":"[email protected]","name":"Jack","gender":"male"},{"id":1003,"email":"[email protected]","name":"Marry","gender":"female"},{"id":1004,"email":"[email protected]","name":"Linda","gender":"female "}]

2、手机客户端程序
      准备好服务端的接口后，接下来就是准备写客户端的程序了。打开Eclipse新建一个OPhone项目。我们创建一个名为MainActivity的Activity类，如下图所示：



       因为要访问外部网络，所以要在AndroidManifest.xml文件里增加一行安全许可：
<uses-permission android:name="android.permission.INTERNET"/>

       这样我们的应用程序就可以访问网络了。

       接着修改布局文件res\layout\main.xml，增加一个TextView对象，用来显示解析后的用户数据。


1.<?xml version= "1.0"  encoding= "utf-8" ?>  
2.<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    
3.    android:orientation="vertical"    
4.    android:layout_width="fill_parent"    
5.    android:layout_height="fill_parent" >  
6.    <TextView android:id="@+id/textView"    
7.        android:layout_width="fill_parent"    
8.        android:layout_height="fill_parent" />  
9.</LinearLayout>  
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <TextView android:id="@+id/textView"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"/>
</LinearLayout>
      OPhone SDK提供了Apache的HttpClient类处理网络访问，相信很多读者朋友都在其他项目当中用到过HttpClient。我写了一个方法，获取某一网址的网页内容，代码如下：


1./**  
2. * 获取网址内容  
3. * @param url  
4. * @return  
5. * @throws Exception  
6. */    
7.private  String getContent(String url)  throws  Exception{  
8.    StringBuilder sb = new  StringBuilder();  
9.      
10.    HttpClient client = new  DefaultHttpClient();  
11.    HttpParams httpParams = client.getParams();  
12.    //设置网络超时参数    
13.    HttpConnectionParams.setConnectionTimeout(httpParams, 3000 );  
14.    HttpConnectionParams.setSoTimeout(httpParams, 5000 );  
15.    HttpResponse response = client.execute(new  HttpGet(url));  
16.    HttpEntity entity = response.getEntity();  
17.    if  (entity !=  null ) {  
18.        BufferedReader reader = new  BufferedReader( new  InputStreamReader(entity.getContent(),  "UTF-8" ),  8192 );  
19.          
20.        String line = null ;  
21.        while  ((line = reader.readLine())!=  null ){  
22.            sb.append(line + "\n" );  
23.        }  
24.        reader.close();  
25.    }  
26.    return  sb.toString();  
27.}  
/**
* 获取网址内容
* @param url
* @return
* @throws Exception
*/
private String getContent(String url) throws Exception{
    StringBuilder sb = new StringBuilder();
    
    HttpClient client = new DefaultHttpClient();
    HttpParams httpParams = client.getParams();
    //设置网络超时参数
    HttpConnectionParams.setConnectionTimeout(httpParams, 3000);
    HttpConnectionParams.setSoTimeout(httpParams, 5000);
    HttpResponse response = client.execute(new HttpGet(url));
    HttpEntity entity = response.getEntity();
    if (entity != null) {
        BufferedReader reader = new BufferedReader(new InputStreamReader(entity.getContent(), "UTF-8"), 8192);
        
        String line = null;
        while ((line = reader.readLine())!= null){
            sb.append(line + "\n");
        }
        reader.close();
    }
    return sb.toString();
}
       修改MainActivity.java，在onCreate方法里增加解析服务端接口内容的代码，如下所示：


1.@Override    
2.public   void  onCreate(Bundle savedInstanceState) {  
3.    super .onCreate(savedInstanceState);  
4.    setContentView(R.layout.main);  
5.      
6.    try {  
7.            StringBuffer sb = new  StringBuffer();  
8.        //在测试过程中，经常是用本机做测试服务器，访问本机的IP地址要设置为10.0.2.2    
9.        String url = "http://10.0.2.2:8080/article/JSONDemoServlet" ;  
10.        String body = getContent(url);  
11.        JSONArray array = new  JSONArray(body);  
12.        for ( int  i= 0 ; i<array.length(); i++){  
13.            JSONObject obj = array.getJSONObject(i);  
14.            sb.append("id:" ).append(obj.getInt( "id" )).append( "\t" );  
15.            sb.append("name:" ).append(obj.getString( "name" )).append( "\r\n" );  
16.            sb.append("gender:" ).append(obj.getString( "gender" )).append( "\t" );  
17.            sb.append("email:" ).append(obj.getString( "email" )).append( "\r\n" );  
18.            sb.append("----------------------\r\n" );  
19.        }  
20.        TextView textView = (TextView)findViewById(R.id.textView);  
21.        textView.setText(sb.toString());  
22.    }catch (Exception e){}  
23.}  
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    
    try{
            StringBuffer sb = new StringBuffer();
        //在测试过程中，经常是用本机做测试服务器，访问本机的IP地址要设置为10.0.2.2
        String url = "http://10.0.2.2:8080/article/JSONDemoServlet";
        String body = getContent(url);
        JSONArray array = new JSONArray(body);
        for(int i=0; i<array.length(); i++){
            JSONObject obj = array.getJSONObject(i);
            sb.append("id:").append(obj.getInt("id")).append("\t");
            sb.append("name:").append(obj.getString("name")).append("\r\n");
            sb.append("gender:").append(obj.getString("gender")).append("\t");
            sb.append("email:").append(obj.getString("email")).append("\r\n");
            sb.append("----------------------\r\n");
        }
        TextView textView = (TextView)findViewById(R.id.textView);
        textView.setText(sb.toString());
    }catch(Exception e){}
}

总结
       本文简单介绍了JSON的相关知识，以及在OPhone平台中如何通过JSON来和服务端的应用进行数据交换。