Android JSON Gson 解析

什么是JSON：

JavaScript Object Notation是一种轻量级的数据交换格式

与xml差异：

+ JSON相对于XML来讲，数据的体积小

+ JSON与JavaScript的交互更加方便

+ JSON的速度要远远快于XML

+ JSON对数据的描述性比XML较差

JSON构成：

(1) 对象：无序的“‘名称/值’对”集合。一个对象以“{”开始，以“}”结束。每个“名称”后跟一个“:”，“‘名称/值’对”之间使用“，”分隔。
(2) 数组：值（value）的有序集合。一个数组以“[”开始，“]”结束。值之间使用“，”分隔。其中，值（value）可以是双引号括起来的字符串（String）、数值(number)、true、false、null、对象(object)或者数组(array)。这些结构可以嵌套。

Gson方法：

数组<--->Json

int[] numbers = {1, 1, 2, 3, 5, 8, 13};
String[] days = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
Gson gson = new Gson();
String numbersJson = gson.toJson(numbers);
String daysJson = gson.toJson(days);
System.out.println("numbersJson = " + numbersJson);//numbersJson = [1,1,2,3,5,8,13]
System.out.println("daysJson = " + daysJson);//daysJson = ["Sun","Mon","Tue","Wed","Thu","Fri","Sat"]
int[] fibonacci = gson.fromJson(numbersJson, int[].class);
String[] weekDays = gson.fromJson(daysJson, String[].class);

集合<--->Json

List<String> names = new ArrayList<String>();
names.add("Alice");
names.add("Bob");
names.add("Carol");
names.add("Mallory");
Gson gson = new Gson();
String jsonNames = gson.toJson(names);//jsonNames = ["Alice","Bob","Carol","Mallory"]
Student a = new Student("Alice", "Apple St", new Date(2000, 10, 1));
Student b = new Student("Bob", "Banana St", null);
Student c = new Student("Carol", "Grape St", new Date(2000, 5, 21));
Student d = new Student("Mallory", "Mango St", null);
List<Student> students = new ArrayList<Student>();
students.add(a);
students.add(b);
students.add(c);
students.add(d);
gson = new Gson();
String jsonStudents = gson.toJson(students);//[{"name":"Alice","address":"Apple St","dateOfBirth":"Nov 1, 3900 12:00:00 AM"},{"name":"Bob","address":"Banana St"},{"name":"Carol","address":"Grape St","dateOfBirth":"Jun 21, 3900 12:00:00 AM"},{"name":"Mallory","address":"Mango St"}]
Type type = new TypeToken<List<Student>>(){}.getType();
List<Student> studentList = gson.fromJson(jsonStudents, type);
Map<--->Json
Map<String, String> colours = new HashMap<String, String>();
colours.put("BLACK", "#000000");
colours.put("RED", "#FF0000");
colours.put("GREEN", "#008000");
colours.put("BLUE", "#0000FF");
colours.put("YELLOW", "#FFFF00");
colours.put("WHITE", "#FFFFFF");
Gson gson = new Gson();
String json = gson.toJson(colours);
//{"WHITE":"#FFFFFF","BLUE":"#0000FF","YELLOW":"#FFFF00","GREEN":"#008000","BLACK":"#000000","RED":"#FF0000"}
Type type = new TypeToken<Map<String, String>>(){}.getType();
Map<String, String> map = gson.fromJson(json, type);
for (String key : map.keySet()) {
    System.out.println("map.get = " + map.get(key));
}

对象<--->Json

Student student = new Student("Duke", "Menlo Park", dob.getTime());
Gson gson = new Gson();
String json = gson.toJson(student);
//{"name":"Duke","address":"Menlo Park","dateOfBirth":"Feb 1, 2000 12:00:00 AM"}
Gson gson = new Gson();
Student student = gson.fromJson(json, Student.class);

嵌套解析

package test0328;

import java.util.Arrays;

public class Person {
 /*
  * {  
  "phone" : ["112233", "445566"], // 数组  
  "name" : "android", // 字符串  
  "age" : 5, // 数值  
  "address" : { "country" : "china", "province" : "ShangHai" }, // 对象  
  "married" : false // 布尔值  
  },
  * 
  */
 
 private String[] phone;

 /**
  * @return the address
  */
 public Address getAddress() {
  return address;
 }

 /**
  * @param address
  *            the address to set
  */
 public void setAddress(Address address) {
  this.address = address;
 }

 private String name;
 private int age;
 private Address address = null;
 private boolean married;

 /**
  * @return the phone
  */
 public String[] getPhone() {
  return phone;
 }

 /**
  * @param phone
  *            the phone to set
  */
 public void setPhone(String[] phone) {
  this.phone = phone;
 }

 /*
  * (non-Javadoc)
  * 
  * @see java.lang.Object#toString()
  */
 @Override
 public String toString() {
  return "Person [phone=" + Arrays.toString(phone) + ", name=" + name
    + ", age=" + age + ", address=" + address + ", married="
    + married + "]";
 }

 /**
  * @return the name
  */
 public String getName() {
  return name;
 }

 /**
  * @param name
  *            the name to set
  */
 public void setName(String name) {
  this.name = name;
 }

 /**
  * @return the age
  */
 public int getAge() {
  return age;
 }

 /**
  * @param age
  *            the age to set
  */
 public void setAge(int age) {
  this.age = age;
 }

 /**
  * @return the married
  */
 public boolean isMarried() {
  return married;
 }

 /**
  * @param married
  *            the married to set
  */
 public void setMarried(boolean married) {
  this.married = married;
 }

}

package test0328;

public class Address {
 // "address" : { "country" : "china", "province" : "ShangHai" }, // 对象  
 private String country;
 private String province;

 /**
  * @return the country
  */
 public String getCountry() {
  return country;
 }

 /**
  * @param country
  *            the country to set
  */
 public void setCountry(String country) {
  this.country = country;
 }

 /**
  * @return the province
  */
 public String getProvince() {
  return province;
 }

 /**
  * @param province
  *            the province to set
  */
 public void setProvince(String province) {
  this.province = province;
 }

 /*
  * (non-Javadoc)
  * 
  * @see java.lang.Object#toString()
  */
 @Override
 public String toString() {
  return "Address [country=" + country + ", province=" + province + "]";
 }

}

package test0328;

import java.io.StringReader;

import com.google.gson.Gson;
import com.google.gson.stream.JsonReader;


public class Json {
 
 /*
 [{  
  "phone" : ["112233", "445566"], // 数组  
  "name" : "android", // 字符串  
  "age" : 5, // 数值  
  "address" : { "country" : "PRC", "province" : "ShangHai" }, // 对象  
  "married" : false // 布尔值  
  },
  {
  "phone" : ["778899", "224466"], // 数组  
  "name" : "Linux", // 字符串  
  "age" : 15, // 数值  
  "address" : { "country" : "USA", "province" : "NY" }, // 对象  
  "married" : true // 布尔值  
  }] 
  */

 private static final String Json = "[{\"phone\" : [\"112233\", \"445566\"], \"name\" : \"android\",  \"age\" : 5,  \"address\" : { \"country\" : \"china\", \"province\" : \"ShangHai\" },  \"married\" : false},{\"phone\" : [\"778899\", \"224466\"], \"name\" : \"linux\",\"age\" : 15, \"address\" : { \"country\" : \"USA\", \"province\" : \"NY\" },\"married\" : true }]";
 private static Gson gson = new Gson();
 
 public static void main(String[] args) throws Exception  {
  JsonReader reader = new JsonReader(new StringReader(Json));
  reader.beginArray();//开始数组
  while(reader.hasNext()){//循环
   reader.beginObject();//开始对象
   Person person = new Person();
    while(reader.hasNext()){//循环
     String tagName = reader.nextName();
     if("phone".equals(tagName)){
      reader.beginArray();
        String[] phones = new String[2];
        phones[0] = reader.nextString();
        phones[1] = reader.nextString();
        person.setPhone(phones);
      reader.endArray();
     }else if("name".equals(tagName)){
      person.setName(reader.nextString());
     }else if("age".equals(tagName)){
      person.setAge(reader.nextInt());
     }else if("address".equals(tagName)){
      reader.beginObject();
      Address address = new Address();
       while(reader.hasNext()){
        int i = 0;
        String tagName2 = reader.nextName();
        if("country".equals(tagName2)){
         address.setCountry(reader.nextString());
        }else{
         address.setProvince(reader.nextString());
        }
       }
      person.setAddress(address);
      reader.endObject();
     }else if("married".equals(tagName)){
      person.setMarried(reader.nextBoolean());
     }
    }
   
   reader.endObject();
   System.out.println(person);
  }
  reader.endArray();
  
 }
 
 public static int[] intsfromJson(String json){
  return gson.fromJson(json, int[].class);
 }
 
 public static String[] stringsfromJson(String json){
  return gson.fromJson(json, String[].class);
 }
}