I am having problems retrieving associated data

Question

I want to start a relationship but I get an error that I can't understand.

Person.java

@Entity
@Getter
@Setter
@RequiredArgsConstructor
public class Personal implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    private String personName;
    private String personLastName;

    // comment old block 
    // @OneToOne(cascade = CascadeType.ALL)
    // private Address Address;

    // add 
    @OneToOne(cascade = CascadeType.ALL, mappedBy = "person")
    private Address address;
}

Address.java

@Entity
@AllArgsConstructor
@NoArgsConstructor
@Getter
@Setter
public class Address implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @Column(name = "Street")
    private String street;
    @Column(name = "Alley")
    private String alley;
    @Column(name = "District")
    private String district;

    // comment old block 
    // @OneToOne(mappedBy = "Address")
    // private Person person; 

    // add 
    @JoinColumn(name = "id")
    @OneToOne(fetch = FetchType.EAGER)
    @MapsId
    private Person person;

    
    public Adres(String street, String alley, String district, Person person) {
        this.street = street;
        this.alley = alley;
        this.district = district;
        this.person = person; 
    }
}

My Repository

    public String createUser(){
        Person p1 = new Person();
        p1.setId(p1.getId());
        p1.setPersonName("testPerson");
        p1.setPersonLastName("testPerson");
        p1.setAddress(new Address("test","test","test",p1)); // ad person on address constructor 
        personRepository.save(p1);
        return "Save is successful";
    }

AddressService.java

@Service
@RequiredArgsConstructor
public class AdresServices {


    private final AddressRepository addressRepository;


    public Optional<Address> getAddress(Integer id){
        return addressRepository.findById(id);
    }
}

I want to see "person" using address 1. but I get error. When I do mappedBy the program gives an error.

I am successfully saving to the database.

BUT! When I try to bring a member through the address table, or rather when I activate the use of @OneToOne(mappedBy = "x"), my program starts to give an error.

ERROR :

java.lang.StackOverflowError: null
    at java.base/java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1012) ~[na:na]
    at java.base/java.util.concurrent.ConcurrentHashMap.putIfAbsent(ConcurrentHashMap.java:1541) ~[na:na]
    at java.base/java.lang.ClassLoader.getClassLoadingLock(ClassLoader.java:667) ~[na:na]
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:591) ~[na:na]
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:579) ~[na:na]
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178) ~[na:na]
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521) ~[na:na]
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:774) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:178) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:728) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:774) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:178) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:728) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:774) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]

However, I still have the same problem! :) nothing has changed. the record to the database is successful, but it continues to give the same error when I want to retrieve the data

Answer 1

Assuming that the Person is the parent entity and the Address is the child entity in this relation, you should annotate your fields as following:

@Entity
public class Person implements Serializable {

    @OneToOne(cascade = CascadeType.ALL, mappedBy = "person")
    private Address Address;

}

@Entity
public class Address implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @JoinColumn(name = "id")
    @OneToOne(fetch = FetchType.LAZY)
    @MapsId
    private Person person; 

}

The exception most likely occurred because you set the mappedBy on the wrong side of the relationship, namely the child.

Note that with the @MapsId annotation, you don't need to generate a new ID for your address entity as the ID of the parent class is used. This is the recommended approach described by Hibernate maintainer Vlad Mihalcea.

Edit
In your comment you stated that the exception occurs when you try to access the address via a controller. The problem here is that you have a infinite loop in the serialization of your entity (or DTO?) due to address -> person -> address -> person -> ... Check this SO question for a detailed answer on how to fix it.