1.JSON(JavaScript Object Notation) 是一種輕量級的數據交換格式。它基於JavaScript（Standard ECMA-262 3rd Edition - December 1999）的一個子集。 JSON採用完全獨立於語言的文本格式，但是也使用了類似於C語言家族的習慣（包括C, C++, C#, Java, JavaScript, Perl, Python等）。這些特性使JSON成爲理想的數據交換語言。 易於人閱讀和編寫，同時也易於機器解析和生成(網絡傳輸速度)。
2.json的數據格式
1>object
{
"name"aaaaaaaaa:"jackson",
"age":100
}
2>數組
{
“students”:
[
{"name":"jackson","age":100},
{"name":"yu","age":22}
]
}
實例：把服務器端的數據生成json數據格式的返回，在Android客戶端獲取json數據，解析該json格式的數據。
1.使用Json 需要用到一下幾個包，下載這下包放在服務器的項目工程下
json-lib-2.3-jdk15.jar commons-beanutils-1.7.0.jar commons-httpclient-3.1.jar commons-lang-2.3.jar commons-logging-1.0.4.jar commons-collections-3.1.jar ezmorph-1.0.3.jar 2. 在Myeclipse 下新建一個項目，首先新建一個 Json的工具類，通過調用該工具類，可以把數據轉換成Json格式的
public class JsonTools {
public JsonTools() {
// TODO Auto-generated constructor stub
}
/**
* @param key
* 表示json字符串的頭信息
* @param object
* 是對解析的集合的類型
* @return
*/
public static String createJsonString(String key, Object value) {
JSONObject jsonObject = new JSONObject();
jsonObject.put(key, value);
return jsonObject.toString();
}3.給對象賦值
package com.json.service;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.json.domain.Person;
public class JsonService {
public JsonService() {
}
/*
* {"person":{"address":"beijing","id":1001,"name":"jack"}}
*/
public Person getPerson() {
Person person = new Person(1001, "yu", "beijing");
return person;
}
/*
* {"persons":[{"address":"guangxi","id":1001,"name":"jack"},{"address":"guangdong","id":1002,"name":"rose"}]}
*/
public List<Person> getlistPerson() {
List<Person> list = new ArrayList<Person>();
Person person1 = new Person(1001, "yu", "guangxi");
Person person2 = new Person(1002, "rose", "guangdong");
list.add(person1);
list.add(person2);
return list;
}
/*
* {"liststring":["beijing","shanghai","hunan"]}
*/
public List<String> getListString() {
List<String> list = new ArrayList<String>();
list.add("beijing");
list.add("shanghai");
list.add("hunan");
return list;
}
//{"listmap":[{"id":1001,"address":"beijing","name":"jack"},{"id":1002,"address":"shanghai","name":"rose"}]}
public List<Map<String, Object>> getListMaps() {
List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
Map<String, Object> map1 = new HashMap<String, Object>();
map1.put("id", 1001);
map1.put("name", "jack");
map1.put("address", "beijing");
Map<String, Object> map2 = new HashMap<String, Object>();
map2.put("id", 1002);
map2.put("name", "rose");
map2.put("address", "shanghai");
list.add(map1);
list.add(map2);
return list;
}
}4.新建一個Servlet 調用 生成json的方法，然後把生成的json格式的數據輸出到客戶端
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
PrintWriter out = response.getWriter();
String jsonString = "";
String action_flag =request.getParameter("action_flag");
if (action_flag.equals("person")) {
jsonString = JsonTools.createJsonString("person", service
.getPerson());
System.out.println("person");
} else if (action_flag.equals("persons")) {
jsonString = JsonTools.createJsonString("persons", service
.getlistPerson());
System.out.println("persons");
} else if (action_flag.equals("liststring")) {
jsonString = JsonTools.createJsonString("liststring", service
.getListString());
System.out.println("liststring");
} else if (action_flag.equals("listmap")) {
jsonString = JsonTools.createJsonString("listmap", service
.getListMaps());
System.out.println("listmap");
}
out.println(jsonString);
out.flush();
out.close();
}
5.搭建Android客戶端，新建一個HttpClient工具類,獲取服務器端json格式的數據
package com.android.myjson.http;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
public class HttpUtils {
public HttpUtils() {
// TODO Auto-generated constructor stub
}
public static String getJsonContent(String url_path) {
try {
URL url = new URL(url_path);
HttpURLConnection connection = (HttpURLConnection) url
.openConnection();
connection.setConnectTimeout(3000);
connection.setRequestMethod("GET");
connection.setDoInput(true);
int code = connection.getResponseCode();
if (code == 200) {
return changeInputStream(connection.getInputStream());
}
} catch (Exception e) {
// TODO: handle exception
}
return "";
}
private static String changeInputStream(InputStream inputStream) {
// TODO Auto-generated method stub
String jsonString = "";
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
int len = 0;
byte[] data = new byte[1024];
try {
while ((len = inputStream.read(data)) != -1) {
outputStream.write(data, 0, len);
}
jsonString = new String(outputStream.toByteArray());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return jsonString;
}
}6.新建一個Json 工具類解析json 數據
package com.android.myjson.json;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import org.json.JSONArray;
import org.json.JSONObject;
import com.android.myjson.domain.Person;
public class JsonTools {
public JsonTools() {
// TODO Auto-generated constructor stub
}
public static Person getPerson(String key, String jsonString) {
Person person = new Person();
//{"person":{"address":"beijing","id":1001,"name":"jack"}}
try {
JSONObject jsonObject = new JSONObject(jsonString);
JSONObject personObject = jsonObject.getJSONObject("person");
person.setId(personObject.getInt("id"));
person.setName(personObject.getString("name"));
person.setAddress(personObject.getString("address"));
} catch (Exception e) {
// TODO: handle exception
}
return person;
}
public static List<Person> getPersons(String key, String jsonString) {
List<Person> list = new ArrayList<Person>();
//{"persons":[{"address":"guangxi","id":1001,"name":"jack"},{"address":"guangdong","id":1002,"name":"rose"}]}
try {
JSONObject jsonObject = new JSONObject(jsonString);
JSONArray jsonArray = jsonObject.getJSONArray(key);
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject2 = jsonArray.getJSONObject(i);
Person person = new Person();
person.setId(jsonObject2.getInt("id"));
person.setName(jsonObject2.getString("name"));
person.setAddress(jsonObject2.getString("address"));
list.add(person);
}
} catch (Exception e) {
// TODO: handle exception
}
return list;
}
public static List<String> getList(String key, String jsonString) {
List<String> list = new ArrayList<String>();
try {
JSONObject jsonObject = new JSONObject(jsonString);
JSONArray jsonArray = jsonObject.getJSONArray(key);
for (int i = 0; i < jsonArray.length(); i++) {
String msg = jsonArray.getString(i);
list.add(msg);
}
} catch (Exception e) {
// TODO: handle exception
}
return list;
}
public static List<Map<String, Object>> listKeyMaps(String key,
String jsonString) {
List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
try {
JSONObject jsonObject = new JSONObject(jsonString);
JSONArray jsonArray = jsonObject.getJSONArray(key);
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject2 = jsonArray.getJSONObject(i);
Map<String, Object> map = new HashMap<String, Object>();
Iterator<String> iterator = jsonObject2.keys();
while (iterator.hasNext()) {
String json_key = iterator.next();
Object json_value = jsonObject2.get(json_key);
if (json_value == null) {
json_value = "";
}
map.put(json_key, json_value);
}
list.add(map);
}
} catch (Exception e) {
// TODO: handle exception
}
return list;
}
}7.打印出解析後的數據
String path = "http://192.168.191.1:8080/jsonProject/servlet/JsonAction?action_flag=person";
String jsonString = HttpUtils.getJsonContent(path);
Person person = JsonTools.getPerson("person", jsonString);
Log.i(TAG, person.toString());