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 [url=]![]() [/url]
- 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 [url=]![]() [/url]
- 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 [url=]![]() [/url]
- 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 [url=]![]() [/url]
- 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 [url=]![]() [/url]
- 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 [url=]![]() [/url]
- 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.
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