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) {
= 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("tony@toeach.net" );
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("tony@toeach.net");
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("tony@toeach.net" );
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("jack@hotmail.com" );
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("marry@" );
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("linda@21cn.com" );
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("tony@toeach.net");
bean1.setGender("male");
list.add(bean1);
User bean2 = new User();
bean2.setId(1002);
bean2.setName("Jack");
bean2.setEmail("jack@hotmail.com");
bean2.setGender("male");
list.add(bean2);
User bean3 = new User();
bean3.setId(1003);
bean3.setName("Marry");
bean3.setEmail("marry@");
bean3.setGender("female");
list.add(bean3);
User bean4 = new User();
bean4.setId(1004);
bean4.setName("Linda");
bean4.setEmail("linda@21cn.com");
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":"tony@toeach.net","name":"Tony","gender":"male"},{"id":1002,"email":"jack@hotmail.com","name":"Jack","gender":"male"},{"id":1003,"email":"marry@","name":"Marry","gender":"female"},{"id":1004,"email":"linda@21cn.com","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:///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:///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(.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(.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。
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