1. FastJson序列化API

• 方法：JSON.toJSONString
• 序列化 : 是指将Java对象转成json格式字符串的过程。JavaBean对象、List集合对象、Map集合 为应用最广泛的。

1.1 序列化Java对象

• Java 中的 Student 对象 序列化 为 JSON 格式 字符串

@Test
public void objectToJson(){
    Student student = new Student();
    student.setId(1);
    student.setName("兮动人");
    student.setAge(24);
    student.setAddress("深圳市");
    student.setFlag(true);

    String jsonString = JSON.toJSONString(student);
    System.out.println(jsonString);
}

{
    "address":"深圳市",
    "age":24,
    "flag":true,
    "id":1,
    "name":"兮动人"
    
}

1.2 序列化List集合

@Test
public void listToJson(){
    Student student = new Student();
    student.setId(1);
    student.setName("兮动人");
    student.setAge(24);
    student.setAddress("深圳市");
    student.setFlag(true);

    Student student2 = new Student();
    student2.setId(2);
    student2.setName("Mike");
    student2.setAge(25);
    student2.setAddress("北京市");
    student2.setFlag(false);

    List<Student> list = new ArrayList<Student>();
    list.add(student);
    list.add(student2);

    String jsonString = JSON.toJSONString(list);
    System.out.println(jsonString);
}

[{
"address":"深圳市","age":24,"flag":true,
"id":1,"name":"兮动人"},{"address":"北京市","age":25,"flag":false,"id":2,"name":"Mike"}]

• 可以观察到 JSON 默认排序是按a-z字母顺序排的

[
    {
        "address":"深圳市",
        "age":24,
        "flag":true,
        "id":1,
        "name":"兮动人"
    },
    {
        "address":"北京市",
        "age":25,
        "flag":false,
        "id":2,
        "name":"Mike"
    }
]

1.3 序列化Map集合

@Test
public void mapToJson(){
    Student student = new Student();
    student.setId(1);
    student.setName("兮动人");
    student.setAge(24);
    student.setAddress("深圳市");
    student.setFlag(true);

    Student student2 = new Student();
    student2.setId(2);
    student2.setName("Mike");
    student2.setAge(25);
    student2.setAddress("北京市");
    student2.setFlag(false);

    Map<String,Student> map = new HashMap<String, Student>();
    map.put("s1",student);
    map.put("s2",student2);
    
    String jsonString = JSON.toJSONString(map);
    System.out.println(jsonString);
}

{
    "s1":{
        "address":"深圳市",
        "age":24,
        "flag":true,
        "id":1,
        "name":"兮动人"
    },
    "s2":{
        "address":"北京市",
        "age":25,
        "flag":false,
        "id":2,
        "name":"Mike"
    }
}

2. FashJson反序列化API

• 反序列化：JSON 格式字符串，反序列化为 Java 对象

2.1 反序列化Java对象

• 方法：JSON.parseObject

@Test
public void jsonToObject(){
   String jsonString = "{\"address\":\"深圳市\",\"age\":24,\"flag\":true,\"id\":1,\"name\":\"兮动人\"}";
   Student student = JSON.parseObject(jsonString, Student.class);
   System.out.println(student);
}

Student(id=1, name=兮动人, age=24, address=深圳市, flag=true)

2.2 反序列化List集合

• 方法：JSON.parseArray

@Test
public void jsonToList(){
    String jsonString = "[{\"address\":\"深圳市\",\"age\":24,\"flag\":true,\"id\":1,\"name\":\"兮动人\"}," +
        "{\"address\":\"北京市\",\"age\":25,\"flag\":false,\"id\":2,\"name\":\"Mike\"}]";
    List<Student> list = JSON.parseArray(jsonString,Student.class);
    for (int i = 0; i < list.size(); i++) {
        Student student =  list.get(i);
        System.out.println(student);
    }
}

Student(id=1, name=兮动人, age=24, address=深圳市, flag=true)
Student(id=2, name=Mike, age=25, address=北京市, flag=false)

2.3 反序列化Map集合

• 方法：JSON.parseObject

@Test
public void jsonToMap(){
    String jsonString = "{\"s1\":{\"address\":\"深圳市\",\"age\":24,\"flag\":true,\"id\":1,\"name\":\"兮动人\"}," +
        "\"s2\":{\"address\":\"北京市\",\"age\":25,\"flag\":false,\"id\":2,\"name\":\"Mike\"}}";
    Map<String,Student> parse = JSON.parseObject(jsonString,new TypeReference<Map<String,Student>>(){});

    for(String s : parse.keySet()){
        System.out.println(s + ":"+parse.get(s));
    }
}

s1:Student(id=1, name=兮动人, age=24, address=深圳市, flag=true)
s2:Student(id=2, name=Mike, age=25, address=北京市, flag=false)

3. SerializerFeature枚举

• 该枚举支持序列化的一些特性数据定义

3.1 WriteMapNullValue

• 枚举常量 WriteMapNullValue 序列化为 null 的字段

@Test
public void testSerializerFeature(){

    Student student = new Student();
    student.setId(1);
    student.setName("兮动人");
    student.setAge(24);
//        student.setAddress("深圳市");
    student.setFlag(true);
    
    String jsonString = JSON.toJSONString(student, SerializerFeature.WriteMapNullValue);
    System.out.println(jsonString);
}

{"address":null,"age":24,"flag":true,"id":1,"name":"兮动人"}

3.2 WriteNullStringAsEmpty

• 枚举常量 WriteNullStringAsEmpty 字段为null，序列化为""

String jsonString = JSON.toJSONString(student, SerializerFeature.WriteNullStringAsEmpty);

{"address":"","age":24,"flag":true,"id":1,"name":"兮动人"}

3.3 WriteNullNumberAsZero

• 枚举常量 WriteNullNumberAsZero 字段为null，序列化为0

@Test
public void testAsZero(){
    Student student = new Student();
    student.setId(1);
    student.setName("兮动人");
//        student.setAge(24);
    student.setAddress("深圳市");
    student.setFlag(true);

    String jsonString = JSON.toJSONString(student, SerializerFeature.WriteNullNumberAsZero);
    System.out.println(jsonString);
}

{"address":"深圳市","age":0,"flag":true,"id":1,"name":"兮动人"}

3.4 WriteNullBooleanAsFalse

• 枚举常量 WriteNullBooleanAsFalse 字段值为null 输出false

@Test
public void testAsFalse(){
    Student student = new Student();
    student.setId(1);
    student.setName("兮动人");
    student.setAge(24);
    student.setAddress("深圳市");
//        student.setFlag(true);

    String jsonString = JSON.toJSONString(student, SerializerFeature.WriteNullBooleanAsFalse);
    System.out.println(jsonString);
}

3.5 WriteDateUseDateFormat

• 枚举常量 WriteDateUseDateFormat 格式化日期格式

  • 没有加属性的情况下，序列化话，日期显示的是毫秒值

@Test
 public void testDateFormat(){
     Student student = new Student();
     student.setId(1);
     student.setName("兮动人");
     student.setAge(24);
     student.setAddress("深圳市");
     student.setFlag(true);
     student.setBirthDate(new Date());

     String jsonString = JSON.toJSONString(student);
     System.out.println(jsonString);
 }

• 加上格式化日期后：

String jsonString = JSON.toJSONString(student, SerializerFeature.WriteDateUseDateFormat);

3.6 PrettyFormat

• 也可以在后面都加上枚举常量 PrettyFormat格式化输出，一目了然

String jsonString = JSON.toJSONString(student,SerializerFeature.WriteDateUseDateFormat, 
SerializerFeature.PrettyFormat);

4. JSonField 注解

该注解作用于方法上,字段上和参数上，可在序列化和反序列化时进行特性功能定制。

1、 注解属性 : name 序列化后的名字

@Data
public class Student {

    private Integer id;

    @JSONField(name = "studentName")
    private String name;

    private Integer age;

    private String address;

    private boolean flag;

    private Date birthDate;

}

@Test
public void testName() {
    Student student = new Student();
    student.setId(1);
    student.setName("兮动人");
    student.setAge(24);
    student.setAddress("深圳市");
    student.setFlag(true);
    student.setBirthDate(new Date());

    String jsonString = JSON.toJSONString(student);
    System.out.println(jsonString);
}

2、注解属性 : ordinal序列化后字段的顺序，属性值越小，顺序越靠前

• 可以看到上面序列化话默认的顺序是按照 a-z 字幕顺序来排序的
• 给字段设置顺序的属性值

@JSONField(name = "studentName", ordinal = 1)
private String name;
@JSONField(ordinal = 2)
private Integer age;

• 发现 值越小，就越靠前

3、注解属性 : format 指定序列化后的格式

@JSONField(format = "YYYY-MM-dd")
private Date birthDate;

4、注解属性 : serialize 指定是否序列化该字段，默认为 true

@JSONField(serialize = false)
private String address;

• 可以发现并没有序列化 address 字段

5、注解属性 : deserialize 指定是否反序列化该字段，默认为 true

6、注解属性 : serialzeFeatures 指定序列化时的特性定义

• 这个属性的用法和上面的 SerializerFeature枚举 用法是一致的

5. JSonType 注解

该注解作用于类上，对该类的字段进行序列化和反序列化时的特性功能定制。

1、注解属性 : includes 要被序列化的字段

@Data
@JSONType(includes = {"id", "name", "age"})
public class Person {
    private int id;
    private String name;
    private int age;
    private String address;
}

@Test
public void test() {
    Person person = new Person();
    person.setId(1);
    person.setName("兮动人");
    person.setAge(23);
    person.setAddress("北京市");

    String s = JSON.toJSONString(person);
    System.out.println(s);
}

• 可以看到并没有序列化 address 字段、

2、注解属性 : orders 序列化后的顺序

@Data
@JSONType(includes = {"id", "name", "age", "address"}, orders = {"name", "age", "address", "id"})
public class Person {
    private int id;
    private String name;
    private int age;
    private String address;
}

@Test
public void test() {
    Person person = new Person();
    person.setId(1);
    person.setName("兮动人");
    person.setAge(23);
    person.setAddress("北京市");

    String s = JSON.toJSONString(person);
    System.out.println(s);
}

3、注解属性 : serialzeFeatures 序列化时的特性定义

• serialzeFeatures 实现和上面案例上的枚举效果是一样的