如何使用杰克逊注释（或任何其他方式）在反序列化中获取复杂数据？

Question

I use Entity Models with json serialization/deserialization to store/retrieve data . I face issue to deserialize Lazy loaded data.

That is, I have defined my entity,superclass, interface like this;

ATG Class

@Entity
@Table(name = "atg", uniqueConstraints = @UniqueConstraint(columnNames = "code"))
public class ATG extends ParentEntity {

    @JsonInclude(JsonInclude.Include.NON_EMPTY)
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "companyid")
    Manufacturer manufacturer;

    getManufacturer();
    setManufacturer();    
}

Customer class

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class Customer implements HasCustomer {

    @JsonInclude(JsonInclude.Include.NON_EMPTY)
    @ManyToOne(cascade = CascadeType.PERSIST, fetch = FetchType.LAZY)
    @JoinColumn(name = "customer2_id", nullable = true)
    private Customer customer;

    getCustomer();
    setCustomer();
}

ParentEntity

@MappedSuperclass
public abstract class ParentEntity implements  HasCustomer{

    @JsonInclude(JsonInclude.Include.NON_EMPTY)
    @ManyToOne( fetch = FetchType.LAZY)
    @JoinColumn(name = "customer2_id", nullable = false)
    private Customer customer;

    getCustomer();
    setCustomer();
}

HasCustomer Interface

public interface HasCustomer extends Serializable{

    public Customer getCustomer();

    public void setCustomer(final Customer customer);

    public Long getCustomerId();

    public void setCustomerId(final Long customerId);
}

Customer Class has a reference to customer object(logical requirement).

I make REST calls to my service endpoints to retrieve data from the database. Ide fined those complex dataTypes as fetch = FetchType.LAZY. When user really requires those data with the response , he will specify. So, at the backend we fetch data by setting FetchMode.JOIN. (This works).

Only problem is, Json annotations. How should i specify annotations in this case? If I keep jsonIgnore at one level, it may block results or I see results all the time when user is not requested to fetch the complex data

I tried @jsonIgnore / @jsonproperty annotations on all getters, setters and the in the variable definition. (I believe I tried all combinations :)

But none is returning the desired results.

I want to keep proper annotation to retrieve customer data and manufacturer data when making calls to ATG service

Can anybody help me out?

I use jackson(com.fasterxml.jackson) V 2.6.3 hibernate v 5.2.1.Final.

Answer 1

I'm not sure you should be using Jackson like this, but this may help.

Define a customer serializer

public class CustomerSerializer extends JsonDeserializer<Customer> {

   public Customer deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JsonProcessingException {
        ....
    }
}

Then use it in your interface

@JsonDeserialize(using = CustomerSerializer.class)
public class Customer implements HasCustomer {