Json解析精讲

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json解析可分为三种形式

原生的解析

谷歌的 Gson

阿里巴巴的 fastjson

以{开头首先创建对象

[ 数组

{key:value,key2:vaule2...}

{key:value,key:{key:value....}}

{key:value,key:[{key:value...},{}...]}

[{key:value},{key:value}...]

原生的解析:

{} 创建jsonOBject

[]jsonArray

通过object对象得到 getString("json中的key")

推荐将数据存储到对象中

1入门

/**
 * 只有一个对象{....}
 *
 */
public class Test {
​
    public static void main(String[] args) throws JSONException {
        String json = "{name:'zhangsan',age:20,sex:'男'}";
        
        // 使用原生的解析方式  解析
        
        // 如果是对象         将json格式的string字符串装载到json对象中
        JSONObject  object = new JSONObject(json);
        // 获得object中的数据
        String name = object.getString("name");
        int age = object.getInt("age");
        String sex = object.getString("sex");
        
        System.out.println(name+"  "+age+"  "+sex);
    }
}

2对象套对象

/**
 * 对象套这对象
 * {}
 * key:{}
 */
public class Test2 {
​
    public static void main(String[] args) throws JSONException {
        String json= "{person:{name:'tom',age:34}}";
        // 得到最外面的 对象
        JSONObject object = new JSONObject(json);
        // 根据perosn键得到后面的对象
        JSONObject object2 = object.getJSONObject("person");
        // 后面的对象得到 里面的value
        String name = object2.getString("name");
        int age= object2.getInt("age");
        System.out.println(name+""+age);
        
    }
}

3用集合和类对象返回

public class Test3 {
​
    public static void main(String[] args) throws JSONException {
        String json = "{name:'jack',age:20,dept:{no:1,deptname:'android开发部'}}";
        
        JSONObject object = new JSONObject(json);
        
        String name = object.getString("name");
        int age = object.getInt("age");
        
        JSONObject object2 = object.getJSONObject("dept");
        int no= object2.getInt("no");
        String deptname = object2.getString("deptname");
        
        System.out.println(name+" "+age+" "+no  +" "+deptname);
        
        // 如果返回可以使用一个map集合返回
        Map<String,Object> map = new HashMap<>();
        map.put("name", name);
        map.put("age", age);
        map.put("no", no);
        map.put("deptname", deptname);
        
        // 以一个类的对象的形式返回
        
        Person person = new Person();
        person.setName(name);
        person.setAge(age);
        Dept dept = new Dept();
        dept.setNo(no);
        dept.setDeptname(deptname);
        person.setDept(dept);
        System.out.println(person);
        
    }
}

public class Dept {
​
    int no;
    String deptname;
    @Override
    public String toString() {
        return "Dept [no=" + no + ", deptname=" + deptname + "]";
    }
    public int getNo() {
        return no;
    }
    public void setNo(int no) {
        this.no = no;
    }
    public String getDeptname() {
        return deptname;
    }
    public void setDeptname(String deptname) {
        this.deptname = deptname;
    }
    
    
}

public class Person {
​
    String name;
    int  age;
    Dept dept;
    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 Dept getDept() {
        return dept;
    }
    public void setDept(Dept dept) {
        this.dept = dept;
    }
    @Override
    public String toString() {
        return "Person [name=" + name + ", age=" + age + ", dept=" + dept + "]";
    }
    
    
}

4一个大数组

public class Test4 {
​
    public static void main(String[] args) throws JSONException {
        String json = "[{name:'tom',age:24},{name:'cindy',age:24},{name:'mandy',age:27},{name:'jerry',age:30}]";
    
        JSONArray array = new JSONArray(json);
        
        List<Map<String, Object>> list = new ArrayList<>();
        List<Person> list2 = new ArrayList<>();
        
        for (int i = 0; i < array.length(); i++) {
            
            JSONObject object = array.getJSONObject(i);
            String name = object.getString("name");
            int age = object.getInt("age");
            // 以list集合套map集合形式装数据的
            Map<String, Object> map = new HashMap<>();
            map.put("name", name);
            map.put("age", age);
            list.add(map);
            // 以list集合套  对象的形式
            Person person = new Person(name, age);
            list2.add(person);
        }
        
        
        
    }
}

5集合装对象返回

public class Test5 {
​
    public static void main(String[] args) throws JSONException {
        String json = "{person:[{name:'tom',age:24},{name:'cindy',age:24},{name:'mandy',age:27},{name:'jerry',age:30}]}";
    
        JSONObject object = new JSONObject(json);
        
        JSONArray array = object.getJSONArray("person");
        // 集合一定要在  循环外面创建
        List<Person> list = new ArrayList<>();
        
        for (int i = 0; i < array.length(); i++) {
            
            JSONObject object2 = array.getJSONObject(i);
            String name = object2.getString("name");
            int age = object2.getInt("age");
            
            Person person = new Person(name, age);
            list.add(person);
        }
        
        System.out.println(list);
    }
}

5用迭代器的方法

public class Test6 {
​
    public static void main(String[] args) throws JSONException {
        String json = "{key1:value1,key2:value2,key3:value3}";
        // 另外一种解析方式
        //1
        JSONObject object= new JSONObject(json);
        // 2  采用迭代器
        // 把所有的键都放在迭代器中
        Iterator iterator = object.keys();
        
        while(iterator.hasNext()){
            // 获取key
            Object key = iterator.next();
            // 通过key 获取value
            Object value = object.get(key.toString());
            System.out.println(value);
            
        }
        
        
    }
}