Android入門：通過JSON資料與伺服器進行通訊

文章目錄

• 伺服器端核心代碼：
• 用戶端核心代碼：

我們完成“Android入門：通過XML資料與伺服器進行通訊“同樣的功能，只是資料轉送使用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格式資料和產生JSON格式資料；

(3)Android中已經整合了JSON的包；

一、核心代碼介紹伺服器端核心代碼：

(1)JSONStringer stringer = new JSONStringer();

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

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

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

用戶端核心代碼：

(1)JSONArray array = new JSONArray(String str);
//將字串轉為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、全部代碼伺服器端：

ListServlet.java

package org.xiazdong.servlet;import java.io.IOException;import java.util.ArrayList;import java.util.List;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.json.JSONStringer;import org.xiazdong.domain.Person;@WebServlet("/ListServlet")public class ListServlet extends HttpServlet {private static final long serialVersionUID = 1L;protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doPost(request,response);}protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {List<Person> list = new ArrayList<Person>();for(int i=0;i<4;i++){Person person = new Person(i,"xiazdong-"+i,20+i);list.add(person);}//將List<Person>組織成JSON字串JSONStringer stringer = new JSONStringer();try{stringer.array();for(Person person:list){stringer.object().key("id").value(person.getId()).key("name").value(person.getName()).key("age").value(person.getAge()).endObject();}stringer.endArray();}catch(Exception e){}response.getOutputStream().write(stringer.toString().getBytes("UTF-8"));response.setContentType("text/json; charset=UTF-8");  //JSON的類型為text/json}}

在瀏覽器中訪問效果如下：

用戶端：

MainActivity.java

package org.xiazdong.personlist;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import org.json.JSONArray;import org.json.JSONObject;import org.xiazdong.domain.Person;import org.xmlpull.v1.XmlPullParser;import android.app.Activity;import android.os.Bundle;import android.util.Log;import android.util.Xml;import android.widget.ListView;import android.widget.SimpleAdapter;public class MainActivity extends Activity {private ListView listView;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);listView = (ListView) this.findViewById(R.id.listview);List<Person> persons = null;try {persons = getJSONData();} catch (Exception e) {e.printStackTrace();}List<Map<String, Object>> maps = new ArrayList<Map<String, Object>>();for (Person person : persons) {HashMap<String, Object> map = new HashMap<String, Object>();map.put("id", person.getId());map.put("name", person.getName());map.put("age", person.getAge());maps.add(map);}SimpleAdapter adapter = new SimpleAdapter(this, maps, R.layout.item,new String[] { "id", "name", "age" }, new int[] { R.id.id,R.id.name, R.id.age });listView.setAdapter(adapter);}//讀取JSON資料並轉為List<Person>private List<Person> getJSONData() throws Exception {List<Person> persons = new ArrayList<Person>();URL url = new URL("http://192.168.0.103:8080/Server/ListServlet");HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");if (conn.getResponseCode() == 200) {InputStream in = conn.getInputStream();persons = parseJSON(in);}return persons;}private List<Person> parseJSON(InputStream in)throws Exception{List<Person> persons = new ArrayList<Person>();Person person = null;String str = read(in);JSONArray array = new JSONArray(str);int length = array.length();for(int i=0;i<length;i++){JSONObject object = array.getJSONObject(i);person = new Person(object.getInt("id"), object.getString("name"), object.getInt("age"));persons.add(person);}return persons;}private String read(InputStream in) throws IOException {byte[] data;ByteArrayOutputStream bout = new ByteArrayOutputStream();byte[]buf = new byte[1024];int len = 0;while((len = in.read(buf))!=-1){bout.write(buf, 0, len);}data = bout.toByteArray();return new String(data,"UTF-8");}}

總結：

JSON和XML都是資料轉送的兩種格式；