Android入門：通過JSON數據與服務器進行通信

我們完成“Android入門：通過JSON數據與服務器進行通信“同樣的功能，只是數據傳輸使用JSON而不是XML；

注意點：

(1)當返回JSON時，content-type為text/json；

(2)通過JSON包進行解析JSON格式數據和生成JSON格式數據；

(3)Android中已經集成了JSON的包；

相關閱讀：Android入門：通過XML數據與服務器進行通信 http://www.linuxidc.com/Linux/2012-07/64597.htm

一、核心代碼介紹

服務器端核心代碼：

(1)JSONStringer stringer = new JSONStringer();

(2)stringer.array().endArray();

(3)stringer.object().key("key").value("value").endObject();

(4)String str = stringer.toString();

客戶端核心代碼：

(1)JSONArray array = new JSONArray(String str); //將字符串轉為JSONArray格式

(2)JSONObject object = array.getJSONObject(int index);

(3)int value = object.getInt(String name);

(4)String value = object.getString(String name);

二、全部代碼

ListServlet.java

1. package org.xiazdong.servlet;
3. import java.io.IOException;
4. import java.util.ArrayList;
5. import java.util.List;
7. import javax.servlet.ServletException;
8. import javax.servlet.annotation.WebServlet;
9. import javax.servlet.http.HttpServlet;
10. import javax.servlet.http.HttpServletRequest;
11. import javax.servlet.http.HttpServletResponse;
13. import org.json.JSONStringer;
14. import org.xiazdong.domain.Person;
17. @WebServlet("/ListServlet")
18. public class ListServlet extends HttpServlet {
19. private static final long serialVersionUID = 1L;
21. protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
22. doPost(request,response);
23. }
25. protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
26. List<Person> list = new ArrayList<Person>();
27. for(int i=0;i<4;i++){
28. Person person = new Person(i,"xiazdong-"+i,20+i);
29. list.add(person);
30. }
31. //將List<Person>組織成JSON字符串
32. JSONStringer stringer = new JSONStringer();
33. try{
34. stringer.array();
35. for(Person person:list){
36. stringer.object().key("id").value(person.getId()).key("name").value(person.getName()).key("age").value(person.getAge()).endObject();
37. }
38. stringer.endArray();
39. }
40. catch(Exception e){}
41. response.getOutputStream().write(stringer.toString().getBytes("UTF-8"));
42. response.setContentType("text/json; charset=UTF-8"); //JSON的類型為text/json
43. }
45. }

在浏覽器中訪問效果如下：

客戶端：

MainActivity.java

1. package org.xiazdong.personlist;
3. import java.io.ByteArrayOutputStream;
4. import java.io.IOException;
5. import java.io.InputStream;
6. import java.net.HttpURLConnection;
7. import java.net.URL;
8. import java.util.ArrayList;
9. import java.util.HashMap;
10. import java.util.List;
11. import java.util.Map;
13. import org.json.JSONArray;
14. import org.json.JSONObject;
15. import org.xiazdong.domain.Person;
16. import org.xmlpull.v1.XmlPullParser;
18. import android.app.Activity;
19. import android.os.Bundle;
20. import android.util.Log;
21. import android.util.Xml;
22. import android.widget.ListView;
23. import android.widget.SimpleAdapter;
25. public class MainActivity extends Activity {
26. private ListView listView;
28. @Override
29. public void onCreate(Bundle savedInstanceState) {
30. super.onCreate(savedInstanceState);
31. setContentView(R.layout.main);
32. listView = (ListView) this.findViewById(R.id.listview);
33. List<Person> persons = null;
34. try {
35. persons = getJSONData();
36. } catch (Exception e) {
37. e.printStackTrace();
38. }
39. List<Map<String, Object>> maps = new ArrayList<Map<String, Object>>();
40. for (Person person : persons) {
41. HashMap<String, Object> map = new HashMap<String, Object>();
42. map.put("id", person.getId());
43. map.put("name", person.getName());
44. map.put("age", person.getAge());
45. maps.add(map);
46. }
47. SimpleAdapter adapter = new SimpleAdapter(this, maps, R.layout.item,
48. new String[] { "id", "name", "age" }, new int[] { R.id.id,
49. R.id.name, R.id.age });
50. listView.setAdapter(adapter);
51. }
53. //讀取JSON數據並轉為List<Person>
54. private List<Person> getJSONData() throws Exception {
55. List<Person> persons = new ArrayList<Person>();
56. URL url = new URL("http://192.168.0.103:8080/Server/ListServlet");
57. HttpURLConnection conn = (HttpURLConnection) url.openConnection();
58. conn.setRequestMethod("GET");
59. if (conn.getResponseCode() == 200) {
60. InputStream in = conn.getInputStream();
61. persons = parseJSON(in);
62. }
63. return persons;
65. }
66. private List<Person> parseJSON(InputStream in)throws Exception{
67. List<Person> persons = new ArrayList<Person>();
68. Person person = null;
69. String str = read(in);
70. JSONArray array = new JSONArray(str);
71. int length = array.length();
72. for(int i=0;i<length;i++){
73. JSONObject object = array.getJSONObject(i);
74. person = new Person(object.getInt("id"), object.getString("name"), object.getInt("age"));
75. persons.add(person);
76. }
77. return persons;
78. }
79. private String read(InputStream in) throws IOException {
80. byte[] data;
81. ByteArrayOutputStream bout = new ByteArrayOutputStream();
82. byte[]buf = new byte[1024];
83. int len = 0;
84. while((len = in.read(buf))!=-1){
85. bout.write(buf, 0, len);
86. }
87. data = bout.toByteArray();
88. return new String(data,"UTF-8");
89. }
90. }

總結：

JSON和XML都是數據傳輸的兩種格式；