设置Json对象输出字段顺序

场景

通过情况下对前端输出json格式不需要关注字段顺序，但某些特殊场景需要设置字段输出顺序(例nginx需要对特殊字段顺序进行加密处理)；框架有默认的顺序，如 jackson 默认使用字段声明的顺序， fastjson 默认是使用字典序。

jackson

使用@JsonPropertyOrder指定顺序

public class JacksonController {

    public static void main(String[] args) throws JsonProcessingException {
        //1: 默认顺序:字段声明的顺序
        Cat1 cat1 = new Cat1();
        cat1.setAge(1);
        cat1.setName("咪咪");
        cat1.setHobby("sleep");
        ObjectMapper objectMapper = new ObjectMapper();
        String json = objectMapper.writeValueAsString(cat1);
        System.out.println("json:"+json.toString());

        //2: 使用@JsonPropertyOrder指定顺序
        Cat2 cat2 = new Cat2();
        cat2.setAge(1);
        cat2.setName("咪咪002");
        cat2.setHobby("eat");
        String json2 = objectMapper.writeValueAsString(cat2);
        System.out.println("json2:"+json2.toString());
    }
}

@Data
class Cat1 {
    private String hobby;
    private String name;
    private Integer age;
}

@Data
@JsonPropertyOrder({"name", "age", "hobby"})
class Cat2 {
    private String hobby;
    private String name;
    private Integer age;
}

fastjson

1、使用@JsonField的ordinal指定顺序，数越小优先级越高，默认为0
2、使用@JSONType的orders属性指定字段顺序

public class FastjsonController {

    public static void main(String[] args){
        //1: 默认顺序:字段声明的顺序
        Dog1 dog1 = new Dog1();
        dog1.setAge(1);
        dog1.setName("嘟嘟001");
        dog1.setHobby("eat");
        String json = JSON.toJSONString(dog1);
        System.out.println("默认顺序(字段声明的顺序):"+json.toString());

        //2: 使用@JsonField的ordinal指定顺序，数越小优先级越高，默认为0
        Dog2 dog2 = new Dog2();
        dog2.setAge(1);
        dog2.setName("嘟嘟002");
        dog2.setHobby("eat");
        String json2 = JSON.toJSONString(dog2);
        System.out.println("JsonField ordinal指定顺序:"+json2.toString());

        //3: 使用@JSONType的orders属性指定字段顺序
        Dog3 dog3 = new Dog3();
        dog3.setAge(1);
        dog3.setName("嘟嘟003");
        dog3.setHobby("eat");
        String json3 = JSON.toJSONString(dog3);
        System.out.println("JSONType orders指定顺序:"+json3.toString());
    }
}

@Data
class Dog1 {
    private String hobby;
    private String name;
    private Integer age;
}

@Data
class Dog2 {
    @JSONField(ordinal = 3)
    private String hobby;
    @JSONField(ordinal = 2)
    private String name;
    @JSONField(ordinal = 1)
    private Integer age;
}

@Data
@JSONType(orders = {"name", "age", "hobby"})
class Dog3 {
    private String hobby;
    private String name;
    private Integer age;
}

注意

将json字段串转换成JSON对象时，如要保持原字段顺序，fastjson使用Feature.OrderedField参数；

JSON.parseObject(json, Feature.OrderedField);
SONObject.parseObject(json, Feature.OrderedField);