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("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@163.com" );

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@163.com");

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@163.com","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://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。