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