How to persist one to one asociation?

Support
#1

Hello, I need to establish a one-to-one relationship between classes A and B. Where case A is the owner of the relation and when assigning from call B the value is lost. I leave you an example project.

Thank you

#2

package com.company.sampleonetoone.entity;

import javax.persistence.Entity;
import javax.persistence.Table;
import javax.persistence.Column;
import javax.persistence.FetchType;
import javax.persistence.OneToOne;
import com.haulmont.cuba.core.entity.StandardEntity;

 @Table(name = "SAMPLEONETOONE_B")
 @Entity(name = "sampleonetoone$B")
public class B extends StandardEntity {
private static final long serialVersionUID = -6636144354361612238L;

@Column(name = "FIELD1")
protected String field1;

@OneToOne(fetch = FetchType.LAZY, mappedBy = "b")
protected A a;

public void setField1(String field1) {
    this.field1 = field1;
}

public String getField1() {
    return field1;
}

public void setA(A a) {
    this.a = a;
}

public A getA() {
    return a;
}

}

import javax.persistence.Entity;
 import javax.persistence.Table;
import javax.persistence.Column;
import com.haulmont.cuba.core.entity.StandardEntity;
import javax.persistence.FetchType;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;

 @Table(name = "SAMPLEONETOONE_A")
 @Entity(name = "sampleonetoone$A")
public class A extends StandardEntity {
private static final long serialVersionUID = -3492608347267339251L;

@Column(name = "FIELD1", nullable = false)
protected String field1;

@OneToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "B_ID")
protected B b;

public void setB(B b) {
    this.b = b;
}

public B getB() {
    return b;
}


public void setField1(String field1) {
    this.field1 = field1;
}

public String getField1() {
    return field1;
}


}
#3

an example

#4

an example

#5

As workaround i do the next

 package com.company.sampleonetoone.listener;

import com.company.sampleonetoone.entity.A;
import com.haulmont.cuba.core.Persistence;
import org.springframework.stereotype.Component;
import com.haulmont.cuba.core.listener.BeforeInsertEntityListener;
import com.haulmont.cuba.core.EntityManager;
import com.company.sampleonetoone.entity.B;
import com.haulmont.cuba.core.listener.BeforeUpdateEntityListener;
import com.haulmont.cuba.core.listener.AfterInsertEntityListener;
import java.sql.Connection;
import com.haulmont.cuba.core.listener.AfterUpdateEntityListener;

import javax.inject.Inject;
import com.haulmont.cuba.core.listener.BeforeDeleteEntityListener;

@Component("sampleonetoone_BListener")
public class BListener implements BeforeInsertEntityListener<B>, BeforeUpdateEntityListener<B>,   BeforeDeleteEntityListener<B> {



    @Inject
    protected Persistence persistence;

    @Override
    public void onBeforeInsert(B entity, EntityManager entityManager) {

        if(entity.getA()!=null){
          A a= entityManager.find(entity.getA().getClass(),entity.getA().getUuid());
          a.setB(entity);
          entityManager.persist(a);
        }
    }


    @Override
    public void onBeforeUpdate(B entity, EntityManager entityManager) {

       A aold= (A) persistence.getTools().getOldValue(entity, "a");
       if(aold!=null && (entity.getA()==null || aold.getUuid()!= entity.getA().getUuid())){
           aold.setB(null);
           entityManager.persist(aold);
       }
       if(entity.getA()!=null){
          A a= entityManager.find(A.class,entity.getA().getUuid());
          a.setB(entity);
          entityManager.persist(a);
       }
    }




    @Override
    public void onBeforeDelete(B entity, EntityManager entityManager) {
        A aold= entity.getA();
        if(aold!=null){
           aold.setB(null);
           entityManager.persist(aold);
        }



    }


}
#6

JPA saves relations only from owning side. What about changing the model to make the needed side (or both sides) owning?

#7

Thanks for your answer. My solution does not look elegant. But table A is large and I need the field of relation B to be in table A. Can an ONETOONE association have Both Owning Side? how can I do it?

#8

Yes you can have both sides owning, i.e. having a foreign key column. The current version of Studio does not support it, but you can do it in the entity source code. Just remove the mappedBy attribute from the @OneToOne annotation and add the @JoinColumn annotation, for example:

@Table(name = "SAMPLE_BAR")
@Entity(name = "sample$Bar")
public class Bar extends StandardEntity {

    @OneToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "FOO_ID")
    protected Foo foo;

After that Studio will generate correct database scripts including your manually defined FOO_ID column.