Spring序列，Jackson Json在序列化和反序列化时出现问题

Question

For some use case, I need to convert one POJO to another POJO with the different fields name. I tried using Jackson object mapper. It worked in some extends. However end result is not what I expected.

public class JacksonTest {

    public static void main(String[] args) throws IOException{
        ObjectMapper mapper = new ObjectMapper();
        User user = new User("Deepak", "111", "Singapore");
        UserMap newUser = mapper.convertValue(user, UserMap.class);
        System.out.println("SOUT: " + newUser);
        System.out.println("Jackson: " + mapper.writeValueAsString(newUser));
    }
}

class User {

    User(String name, String id, String address){
        this.name = name;
        this.id = id;
        this.address = address;
    }

    String name;
    String id;
    String address;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

class UserMap implements Serializable {
    @JsonProperty("name")
    String name;

    private Map<String, Object> meta = new HashMap<>();

    @JsonAnyGetter
    public Map<String, Object> any() {
        return meta;
    }

    @JsonAnySetter
    public void set(String name, Object value) {
        meta.put(name, value);
    }

    @Override
    public String toString() {
        return "UserMap{" +
                "name_new='" + name + '\'' +
                ", meta=" + meta.keySet().stream().map(x-> x+ ":: "+ meta.get(x)).collect(Collectors.joining(", ")) +
                '}';
    }
}

If you run, the output would be :

SOUT: UserMap{name_new='Deepak', meta=address:: Singapore, id:: 111}

Jackson: {"name":"Deepak","address":"Singapore","id":"111"}

I am using Springboot which internally uses jackson serializer. It converts the newUser object to normal user class again. I want to serialize string in the way class constructed. I want the output in SOUT format.

Answer 1

I think you misunderstood what the @JsonAnyGetter/@JsonAnySetter pair will, in effect, do.

It allows you to create a almost dynamic bean, with mandatory as well as voluntary fields. In your case, the name would be mandatory, and all other fields voluntary.

What goes on under the hood is not that your UserMap gets converted to a User . What you see is a serialized UserMap, but since it has the same fields and values as the corresponding User instance, their serialized forms look identical.

Answer 2

I couldn't get the auto serialization and deserialization to work using the default Spring boot beans. In the end, this worked well for me after including Project Lombok and apache BeanUtils:

@ToString() @Getter() @Setter() @NoArgsConstructor()
public class User {
    private String email;
    private String bio;
    private String image;
    private String displayName;
    private String userId;
    private long lat;
    private long lng;

    public User(String json) throws JsonParseException, JsonMappingException, IOException, IllegalAccessException, InvocationTargetException {
        ObjectMapper om = new ObjectMapper();
        User u = om.readValue(json, User.class);
        BeanUtils.copyProperties(this, u);
    }
}

http://commons.apache.org/proper/commons-beanutils/download_beanutils.cgi https://projectlombok.org/