一、什么是JSON？
JSON是一种取代XML的数据结构,和xml相比,它更小巧但描述能力却不差,由于它的小巧所以网络传输数据将减少更多流量从而加快速度。
JSON就是一串字符串 只不过元素会使用特定的符号标注。
{} 双括号表示对象
[] 中括号表示数组
"" 双引号内是属性或值
: 冒号表示后者是前者的值(这个值可以是字符串、数字、也可以是另一个数组或对象)
所以 {"name": "Michael"} 可以理解为是一个包含name为Michael的对象
而[{"name": "Michael"},{"name": "Jerry"}]就表示包含两个对象的数组
当然了,你也可以使用{"name":["Michael","Jerry"]}来简化上面一部,这是一个拥有一个name数组的对象
二、JSON解析之传统的JSON解析
1、生成json字符串
public static String createJsonString(String key, Object value) { ???????JSONObject jsonObject = new JSONObject(); ???????jsonObject.put(key, value); ???????return jsonObject.toString();}2、解析JSON字符串
分为以下三种情况，一个JavaBean，一个List数组，一个嵌套Map的List数组：
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;/** * 完成对json数据的解析 * ?*/public class JsonTools { ???public static Person getPerson(String key, String jsonString) { ???????Person person = new Person(); ???????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 getPersons(String key, String jsonString) { ???????List list = new ArrayList(); ???????try { ???????????JSONObject jsonObject = new JSONObject(jsonString); ???????????// 返回json的数组 ???????????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 getList(String key, String jsonString) { ???????List list = new ArrayList(); ???????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> listKeyMaps(String key, ???????????String jsonString) { ???????List> list = new ArrayList>(); ???????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 map = new HashMap(); ???????????????Iterator 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; ???}}三、JSON解析之GSON
1、生成JSON字符串
import com.google.gson.Gson;public class JsonUtils { ???public static String createJsonObject(Object obj) { ???????Gson gson = new Gson(); ???????String str = gson.toJson(obj); ???????return str; ???}}二、解析JSONimport java.util.ArrayList;import java.util.List;import java.util.Map;import com.google.gson.Gson;import com.google.gson.reflect.TypeToken;;public class GsonTools { ???public GsonTools() { ???????// TODO Auto-generated constructor stub ???} ???/** ????* @param ?????* @param jsonString ????* @param cls ????* @return ????*/ ???public static ?T getPerson(String jsonString, Class cls) { ???????T t = null; ???????try { ???????????Gson gson = new Gson(); ???????????t = gson.fromJson(jsonString, cls); ???????} catch (Exception e) { ???????????// TODO: handle exception ???????} ???????return t; ???} ???/** ????* 使用Gson进行解析 List ????* ?????* @param ?????* @param jsonString ????* @param cls ????* @return ????*/ ???public static ?List getPersons(String jsonString, Class cls) { ???????List list = new ArrayList(); ???????try { ???????????Gson gson = new Gson(); ???????????list = gson.fromJson(jsonString, new TypeToken>() { ???????????}.getType()); ???????} catch (Exception e) { ???????} ???????return list; ???} ???/** ????* @param jsonString ????* @return ????*/ ???public static List getList(String jsonString) { ???????List list = new ArrayList(); ???????try { ???????????Gson gson = new Gson(); ???????????list = gson.fromJson(jsonString, new TypeToken>() { ???????????}.getType()); ???????} catch (Exception e) { ???????????// TODO: handle exception ???????} ???????return list; ???} ???public static List> listKeyMaps(String jsonString) { ???????List> list = new ArrayList>(); ???????try { ???????????Gson gson = new Gson(); ???????????list = gson.fromJson(jsonString, ???????????????????new TypeToken>>() { ???????????????????}.getType()); ???????} catch (Exception e) { ???????????// TODO: handle exception ???????} ???????return list; ???}}三、JSON解析之FastJSON
import java.util.ArrayList;import java.util.List;import java.util.Map;import com.alibaba.fastjson.JSON;import com.alibaba.fastjson.TypeReference;public class JsonTool { ???public static ?T getPerson(String jsonstring, Class cls) { ???????T t = null; ???????try { ???????????t = JSON.parseObject(jsonstring, cls); ???????} catch (Exception e) { ???????????// TODO: handle exception ???????} ???????return t; ???} ???public static ?List getPersonList(String jsonstring, Class cls) { ???????List list = new ArrayList(); ???????try { ???????????list = JSON.parseArray(jsonstring, cls); ???????} catch (Exception e) { ???????????// TODO: handle exception ???????} ???????return list; ???} ???public static ?List> getPersonListMap1( ???????????String jsonstring) { ???????List> list = new ArrayList>(); ???????try { ???????????list = JSON.parseObject(jsonstring, ???????????????????new TypeReference>>() { ???????????????????}.getType()); ???????} catch (Exception e) { ???????????// TODO: handle exception ???????} ???????return list; ???}}总结：
JSON对于移动设备来说，尤其对于网络环境较差和流量限制的情况下，相对于XML格式的数据传输会更节省流量，传输效率更高。在这三种解析方式中FastJson是效率最高的，推荐使用。
JSON的三种解析方式
原文地址：http://www.cnblogs.com/jay36/p/7684933.html