开发android客户端需要了解的知识--JSON数据解析

来源：互联网发布：长虹led32538数据编辑：程序博客网时间：2024/05/16 10:04

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:

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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() {
        returnstreet;
    }
    public void setStreet(String street) {
        this.street = street;
    }
    public String getCity() {
        returncity;
    }
    public void setCity(String city) {
        this.city = city;
    }
    public String getCountry() {
        returncountry;
    }
    public void setCountry(String country) {
        this.country = country;
    }
    @Override
    public String toString() {
        return"Address [street=" + street + ", city=" + city + ", country="
                + country + "]";
    }
}

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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() {
        returnname;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        returnage;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public boolean isMale() {
        returnmale;
    }
    public void setMale(boolean male) {
        this.male = male;
    }
    public Address getAddress() {
        returnaddress;
    }
    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:

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JSONObject jsonObject = newJSONObject(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 = newAddress(street, city, country);
Person person = newPerson(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:

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Gson gson = newGson();
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:

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List<Person> persons = newArrayList<Person>();
JSONArray jsonArray = newJSONArray(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 = newAddress(street, city, country);
    Person person = newPerson(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:

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