android筆記--JSON數據解析

什么是JSON:

JSON即JavaScript Object Natation, 它是一種輕量級的數據交換格式, 與XML一樣, 是廣泛被采用的客戶端和服務端交互的解決方案.

JSON對象: JSON中對象(Object)以"{"開始, 以"}"結束. 對象中的每一個item都是一個key-value對, 表現為"key:value"的形式, key-value對之間使用逗號分隔. 如:{"name":"coolxing", "age"=24, "male":true, "address":{"street":"huiLongGuan", "city":"beijing", "country":"china"}}. JSON對象的key只能是string類型的, 而value可以是string, number, false, true, null, Object對象甚至是array數組, 也就是說可以存在嵌套的情況.

JSON數組: JSON數組(array)以"["開始, 以"]"結束, 數組中的每一個元素可以是string, number, false, true, null, Object對象甚至是array數組, 數組間的元素使用逗號分隔. 如["coolxing", 24, {"street":"huiLongGuan", "city":"beijing", "country":"china"}].

 

JSON數據的解析:解析JSON數據, 首先需要明確待解析的是JSON Object還是JSON array, 然后需要確定采用哪種解析技術. android平臺上一般有2種解析技術可供選擇: android內置的org.json包和google的開源gson庫. 以下將分別采用這兩種技術解析JSON對象和JSON數組.

1.  采用android內置的org.json包解析JSON對象. 假設待解析的JSON數據為json = "{\"name\":\"coolxing\", \"age\"=24, \"male\":true, \"address\":{\"street\":\"huiLongGuan\", \"city\":\"beijing\", \"country\":\"china\"}}", 其中\用于轉義表達式中的雙引號. 首先定義2個JavaBean:

public class Address {
	private String street;
	private String city;
	private String country;

	public Address() {
		super();
	}

	public Address(String street, String city, String country) {
		super();
		this.street = street;
		this.city = city;
		this.country = country;
	}

	public String getStreet() {
		return street;
	}

	public void setStreet(String street) {
		this.street = street;
	}

	public String getCity() {
		return city;
	}

	public void setCity(String city) {
		this.city = city;
	}

	public String getCountry() {
		return country;
	}

	public void setCountry(String country) {
		this.country = country;
	}

	@Override
	public String toString() {
		return "Address [street=" + street + ", city=" + city + ", country="
				+ country + "]";
	}

}

public class Person {
	private String name;
	private int age;
	private boolean male;
	private Address address;

	public Person() {
		super();
	}

	public Person(String name, int age, boolean male, Address address) {
		super();
		this.name = name;
		this.age = age;
		this.male = male;
		this.address = address;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public boolean isMale() {
		return male;
	}

	public void setMale(boolean male) {
		this.male = male;
	}

	public Address getAddress() {
		return address;
	}

	public void setAddress(Address address) {
		this.address = address;
	}

	@Override
	public String toString() {
		return "Person [name=" + name + ", age=" + age + ", male=" + male
				+ ", address=" + address + "]";
	}

}

下面是具體的解析代碼:

JSONObject jsonObject = new JSONObject(json);
String name = jsonObject.getString("name");
int age = jsonObject.getInt("age");
boolean male = jsonObject.getBoolean("male");
JSONObject addressJSON = jsonObject.getJSONObject("address");
String street = addressJSON.getString("street");
String city = addressJSON.getString("city");
String country = addressJSON.getString("country");
Address address = new Address(street, city, country);
Person person = new Person(name, age, male, address);
System.out.println(person);

LogCat的輸出為Person [name=coolxing, age=24, male=true, address=Address [street=huiLongGuan, city=beijing, country=china]], 說明已經正確解析了JSON對象.

 

2. 采用gson庫解析JSON對象. 假設帶解析的JSON數據是json = "{\"name\":\"coolxing\", \"age\"=24, \"male\":true, \"address\":{\"street\":\"huiLongGuan\", \"city\":\"beijing\", \"country\":\"china\"}}", 首先需要到http://code.google.com/p/google-gson/下載jar包, 并將其添加到項目中. 具體的解析代碼如下:

Gson gson = new Gson();
Person person = gson.fromJson(json, Person.class);
System.out.println(person);

LogCat的輸出為Person [name=coolxing, age=24, male=true, address=Address [street=huiLongGuan, city=beijing, country=china]], 說明已經正確解析了JSON對象, 是不是很簡單?

 

3. 采用android內置的org.json包解析JSON數組. 假設待解析的JSON數據為json = "[{\"name\":\"coolxing\", \"age\"=24, \"male\":true, \"address\":{\"street\":\"huiLongGuan\", \"city\":\"beijing\", \"country\":\"china\"}}, {\"name\":\"min\", \"age\"=20, \"male\":false, \"address\":{\"street\":\"heiShiJiao\", \"city\":\"daLian\", \"country\":\"china\"}}]", 解析代碼如下:

List<Person> persons = new ArrayList<Person>();
JSONArray jsonArray = new JSONArray(json);
for(int i = 0; i < jsonArray.length(); i++) {
	JSONObject jsonObject = jsonArray.getJSONObject(i);
	String name = jsonObject.getString("name");
	int age = jsonObject.getInt("age");
	boolean male = jsonObject.getBoolean("male");
	JSONObject addressJSON = jsonObject.getJSONObject("address");
	String street = addressJSON.getString("street");
	String city = addressJSON.getString("city");
	String country = addressJSON.getString("country");
	Address address = new Address(street, city, country);
	Person person = new Person(name, age, male, address);
	persons.add(person);
}
System.out.println(persons);

LogCat的輸出為[Person [name=coolxing, age=24, male=true, address=Address [street=huiLongGuan, city=beijing, country=china]], Person [name=min, age=20, male=false, address=Address [street=heiShiJiao, city=daLian, country=china]]], 說明已經正確解析了JSON數組.

4. 采用gson庫解析JSON數組. 待解析的JSON數據同上, 具體代碼為:

Gson gson = new Gson();
Type listType = new TypeToken<List<Person>>(){}.getType();
List<Person> persons = gson.fromJson(json, listType);

LogCat的輸出為[Person [name=coolxing, age=24, male=true, address=Address [street=huiLongGuan, city=beijing, country=china]], Person [name=min, age=20, male=false, address=Address [street=heiShiJiao, city=daLian, country=china]]], 說明已經正確解析了JSON數組.

轉自：http://coolxing.iteye.com/blog/1211403