Jackson扁平化处理对象

普通对象

一般不对对象进行扁平化处理的化是以下格式的，我们不需要显示password和userInfo

{
    "password": {
        "salt": "sdsdcx",
        "password": "12sadtg32"
    },
    "userInfo": {
        "name": "lyra",
        "age": 12
    }
}

业务需要的格式是不加password和userInfo的扁平对象，如下json所示

{
    "salt": "sdsdcx",
    "password": "12sadtg32",
    "name": "lyra",
    "age": 12
}

这时候可以使用在实体类的成员变量中添加Jackson的JsonUnwrapped注解即可
如下代码所示

public class User {
    @JsonUnwrapped
    private Password password;
    @JsonUnwrapped
    private UserInfo userInfo;

    public Password getPassword() {
        return password;
    }

    public void setPassword(Password password) {
        this.password = password;
    }

    public UserInfo getUserInfo() {
        return userInfo;
    }

    public void setUserInfo(UserInfo userInfo) {
        this.userInfo = userInfo;
    }
}

运行后就返回扁平对象了

map

JsonUnwrapped注解是不支持Map对象
有的使用map返回的json是以下格式的

{
    "student": {
        "0": {
            "id": 0,
            "name": "lyra",
            "age": 21
        },
        "1": {
            "id": 1,
            "name": "lyra",
            "age": 21
        },
        "2": {
            "id": 2,
            "name": "lyra",
            "age": 21
        }
    }
}

我们希望是对象紧接着对象，student名称是不需要的，根据StackOverflow的这篇文章，添加map的注解方法即可解决

https://stackoverflow.com/questions/18043587/why-im-not-able-to-unwrap-and-serialize-a-java-map-using-the-jackson-java-libra

public class Grade {
    private Map<String, User> student;

    @JsonAnySetter
    public void addStudent(String key, User value) {
        student.put(key, value);
    }

    @JsonAnyGetter
    public Map<String, User> getStudent() {
        return student;
    }

    public void setStudent(Map<String, User> student) {
        this.student = student;
    }
}

需要注意的是这三部分要保证一致

之后返回的json结果为

{
    "0": {
        "id": 0,
        "name": "lyra",
        "age": 21
    },
    "1": {
        "id": 1,
        "name": "lyra",
        "age": 21
    },
    "2": {
        "id": 2,
        "name": "lyra",
        "age": 21
    }
}