android笔记--JSON数据解析

什么是JSON:

JSON即JavaScript Object Natation, 它是一种轻量级的数据交换格式, 与XML一样, 是广泛被采用的客户端和服务端交互的解决方案.

JSON对象: JSON中对象(Object)以"{"开始, 以"}"结束. 对象中的每一个item都是一个key-value对, 表现为"key:value"的形式, key-value对之间使用逗号分隔. 如:{"name":"coolxing", "age"=24, "male":true, "address":{"street":"huiLongGuan", "city":"beijing", "country":"china"}}. JSON对象的key只能是string类型的, 而value可以是string, number, false, true, null, Object对象甚至是array数组, 也就是说可以存在嵌套的情况.

JSON数组: JSON数组(array)以"["开始, 以"]"结束, 数组中的每一个元素可以是string, number, false, true, null, Object对象甚至是array数组, 数组间的元素使用逗号分隔. 如["coolxing", 24, {"street":"huiLongGuan", "city":"beijing", "country":"china"}].

JSON数据的解析:解析JSON数据, 首先需要明确待解析的是JSON Object还是JSON array, 然后需要确定采用哪种解析技术. android平台上一般有2种解析技术可供选择: android内置的org.json包和google的开源gson库. 以下将分别采用这两种技术解析JSON对象和JSON数组.

1. 采用android内置的org.json包解析JSON对象. 假设待解析的JSON数据为json = "{\"name\":\"coolxing\", \"age\"=24, \"male\":true, \"address\":{\"street\":\"huiLongGuan\", \"city\":\"beijing\", \"country\":\"china\"}}", 其中\用于转义表达式中的双引号. 首先定义2个JavaBean:

Java代码







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 + "]";

}

}

Java代码







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 + "]";

}

}

下面是具体的解析代码:

Java代码







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的输出为Person [name=coolxing, age=24, male=true, address=Address [street=huiLongGuan, city=beijing, country=china]], 说明已经正确解析了JSON对象.

2. 采用gson库解析JSON对象. 假设带解析的JSON数据是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/下载jar包, 并将其添加到项目中. 具体的解析代码如下:

Java代码







Gson gson = new Gson();

Person person = gson.fromJson(json, Person.class);

System.out.println(person);

LogCat的输出为Person [name=coolxing, age=24, male=true, address=Address [street=huiLongGuan, city=beijing, country=china]], 说明已经正确解析了JSON对象, 是不是很简单?

3. 采用android内置的org.json包解析JSON数组. 假设待解析的JSON数据为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\"}}]", 解析代码如下:

Java代码







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的输出为[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]]], 说明已经正确解析了JSON数组.

4. 采用gson库解析JSON数组. 待解析的JSON数据同上, 具体代码为:

Java代码







Gson gson = new Gson();

Type listType = new TypeToken<List<Person>>(){}.getType();

List<Person> persons = gson.fromJson(json, listType);

LogCat的输出为[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]]], 说明已经正确解析了JSON数组.
new TypeToken<List<Person>>(){}.getType(); 这句代码表示创建一个TypeToken的匿名子类对象, 并调用对象的getType()方法.

org.json包和gson库还有很多其他有用的API, 需要的时候可查看文档. 比如有的时候需要通过java对象或java集合和数组生成json数据上传给服务器, 当然你可以自我构造json字符串, 但会很麻烦. 这个时候就可以使用其中的有关API, 方便的完成这项工作.