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); 

 

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.