Android Json解析
JSON(JavaScript Object Notation)是一种轻量级数据交换格式基本结构有对象（JsonObject）、数组（JsonArray）。
Gson是谷歌提供的一个面向对象用来可以快速高效在Java对象和JSON数据之间进行映射的java类库。可以将一个JSON字符串转成一个Java对象，也可以将一个Java对象转换成一个JSON字符串。
Fast-json是阿里巴巴工程师开发的一个性能很好的Java语言实现JSON解析器和生成器，性能极好，据说能超越其他任何的Java JSON解析器。特点是快，功能强大，支持jdk类的任意Javabean类，collection，map，date或enum。无依赖，支持注解和全类型序列化。
JSON简单语法：
{} 双括号表示对象
eg:{“name”: “Xiaoming”} 可以理解为是一个包含name为Xiaoming的对象
[] 中括号表示数组
eg:[{“course”: “Math”},{“course”: “IT”}]就表示包含两个对象的数组
“”双引号内是属性或值
传统的JSON解析
1、生成JSOn字符串
import org.json.JSONException;
import org.json.JSONObject;
public class JsonUtils {
static JSONObject jsonObject = new JSONObject();//生成json对象
public static JSONObject addJsonObject(String key, Object value){
try {
jsonObject.append(key, value);
} catch (JSONException e) {
e.printStackTrace();
}//通过键值对存放json数据
return jsonObject;
}
public static String createJsonString() {
return jsonObject.toString();//返回json格式字符串
}
}
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public class Main {
public static void main(String[] args) {
JsonUtils.addJsonObject("name", "xiaohua");
JsonUtils.addJsonObject("name", "xiaoming");
JsonUtils.addJsonObject("name", "xiaojuan");
JsonUtils.addJsonObject("age", "20");
String jsonString=JsonUtils.createJsonString();
System.out.println("jsonString:"+jsonString);
}
}
输出：
--------------------------------------------------------------
jsonString:{"age":["20"],"name":["xiaohua","xiaoming","xiaojuan"]}2.解析JSON字符串
分为以下三种数据类型，JavaBean，List数组，嵌套Map的List数组：
public class Person {
private int id;
private String name;
private String address;
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 getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
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import java.util.ArrayList;
import java.util.List;
import org.json.JSONArray;
import org.json.JSONObject;
/** * 完成对json数据的解析 * */
public class JsonUtils {
public static Person getPerson(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<Person> getPersons(String key, String jsonString) {
List<Person> list = new ArrayList<Person>();
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<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;
}
}
----------------------------------------------------------------
import java.util.ArrayList;
import java.util.List;
public class Main {
public static void main(String[] args) {
Person person = new Person();
String jsonString ="{\"person\":{\"id\":\"20\",\"name\":\"xiaohua\",\"address\":\"shenzhen\"}}";
person = JsonUtils.getPerson(jsonString);
System.out.println("id:"+person.getId());
System.out.println("name:"+person.getName());
System.out.println("address:"+person.getAddress());
String jsonString1="{\"person\":[{\"id\":\"20\",\"name\":\"xiaohua\",\"address\":\"shenzhen\"},{\"id\":\"21\",\"name\":\"xiaoming\",\"address\":\"shanghai\"},{\"id\":\"22\",\"name\":\"xiaojuan\",\"address\":\"suzhou\"}]}";
List<Person> list = new ArrayList<Person>();
list=JsonUtils.getPersons("person", jsonString1);
for(int i=0;i<list.size();i++){
person=list.get(i);
System.out.println("id:"+person.getId());
System.out.println("name:"+person.getName());
System.out.println("address:"+person.getAddress());
}
}
}
输出：
-------------------------------------------------------------
id:20
name:xiaohua
address:shenzhen
id:20
name:xiaohua
address:shenzhen
id:21
name:xiaoming
address:shanghai
id:22
name:xiaojuan
address:suzhou使用GSON解析
Gson的基本用法：定义实体类，根据需要可以将json生成单个实体或列表实体集合。
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;
}
}
----------------------------------------------------------------
public class Main {
public static void main(String[] args) {
Person person = new Person();
person.setAddress("shenzhen");
person.setId(20);
person.setName("xiaohua");
String jsonresult=JsonUtils.createJsonObject(person);
System.out.println(jsonresult);
}
}
输出结果：
---------------------------------------------------------------
{"id":20,"name":"xiaohua","address":"shenzhen"}2.解析JSON
public class Person {
Person(){
}
private int id;
private String name;
private String address;
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 getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
-------------------------------------------------------------------
import java.util.ArrayList;
import java.util.List;
import org.json.JSONArray;
import org.json.JSONObject;
import com.google.gson.Gson;
public class JsonUtils {
public static <T> T getPerson(String jsonString, Class cls) {
T t = null;
try {
Gson gson = new Gson();
t = (T) gson.fromJson(jsonString, cls);
} catch (Exception e) {
// TODO: handle exception
}
return t;
}
/** * 使用Gson进行解析 List */
public static <T>List<T> getPersons(String key, String jsonString, Class cls) {
List<T> list = new ArrayList<T>();
T t = null;
try {
Gson gson = new Gson();
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);
t = (T) gson.fromJson(jsonObject2.toString(), cls);
list.add(t);
}
} catch (Exception e) {
}
return list;
}
}
--------------------------------------------------------------
import java.util.ArrayList;
import java.util.List;
import com.alibaba.fastjson.JSON;
import com.google.gson.Gson;
public class Main {
public static void main(String[] args) {
Gson gson =new Gson();
Person person = new Person();
String jsonString ="{\"id\":\"20\",\"name\":\"xiaohua\",\"address\":\"shenzhen\"}";
person=gson.fromJson(jsonString, Person.class);
System.out.println("id:"+person.getId());
System.out.println("name:"+person.getName());
System.out.println("address:"+person.getAddress());
String jsonString1="{\"person\":[{\"id\":\"20\",\"name\":\"xiaohua\",\"address\":\"shenzhen\"},{\"id\":\"21\",\"name\":\"xiaoming\",\"address\":\"shanghai\"},{\"id\":\"22\",\"name\":\"xiaojuan\",\"address\":\"suzhou\"}]}";
List<Person> list = new ArrayList<Person>();
list=JsonUtils.getPersons("person", jsonString1, Person.class);
for(int i=0;i<list.size();i++){
person=list.get(i);
System.out.println("id:"+person.getId());
System.out.println("name:"+person.getName());
System.out.println("address:"+person.getAddress());
}
}
}
输出结果：
---------------------------------------------------------------
id:20
name:xiaohua
address:shenzhen
id:20
name:xiaohua
address:shenzhen
id:21
name:xiaoming
address:shanghai
id:22
name:xiaojuan
address:suzhou
使用FastJSon解析
public class Person {
Person(){
}
private int id;
private String name;
private String address;
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 getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
-----------------------------------------------------------
import java.util.ArrayList;
import java.util.List;
import com.alibaba.fastjson.JSON;
public class JsonUtils {
public static <T>T getPerson(String jsonstring, Class cls) {
T t = null;
try {
t = (T) JSON.parseObject(jsonstring, cls);
} catch (Exception e) {
// TODO: handle exception
}
return t;
}
public static List getPersons(String jsonstring, Class cls) {
List list = new ArrayList();
try {
list = JSON.parseArray(jsonstring, cls);
} catch (Exception e) {
// TODO: handle exception
}
return list;
}
}
-----------------------------------------------------------------
import java.util.ArrayList;
import java.util.List;
import com.alibaba.fastjson.JSON;
import com.google.gson.Gson;
public class Main {
public static void main(String[] args) {
Gson gson =new Gson();
Person person = new Person();
String jsonString ="{\"id\":\"20\",\"name\":\"xiaohua\",\"address\":\"shenzhen\"}";
person=gson.fromJson(jsonString, Person.class);
System.out.println("id:"+person.getId());
System.out.println("name:"+person.getName());
System.out.println("address:"+person.getAddress());
String jsonString1="[{\"id\":\"20\",\"name\":\"xiaohua\",\"address\":\"shenzhen\"},{\"id\":\"21\",\"name\":\"xiaoming\",\"address\":\"shanghai\"},{\"id\":\"22\",\"name\":\"xiaojuan\",\"address\":\"suzhou\"}]";
List<Person> list = new ArrayList<Person>();
list=JsonUtils.getPersons( jsonString1, Person.class);
for(int i=0;i<list.size();i++){
person=list.get(i);
System.out.println("id:"+person.getId());
System.out.println("name:"+person.getName());
System.out.println("address:"+person.getAddress());
}
}
}JSON格式数据相对于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。