One To Many Bidirectional relationship implementation postgres SpringBoot

Question

I am seeking the suggestion for implementation of Many-to-One mapping classes and was hoping if anyone could provide me a clear picture.

One to One mapping Scenario: Table foo and Table childfoo Foo has one to many and many to one relationship

Here is the JPA entity implementation I've made so far:

@Entity
@Data
@Table(name = "foo")
public class foo implements Serializable {

/**
 * 
 */
private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "foo_id")
private Integer fooId;


@Column(name="someId")
private Integer someId

@Column(name="comevalue")
private String somevalue;

@OneToMany(mappedBy="foo", fetch=FetchType.LAZY, cascade = CascadeType.ALL)
    private Set<ChildFoo> userRecords = new HashSet<>();
}

ChildFoo class

@Entity
@Data
@NoArgsConstructor
@EqualsAndHashCode(exclude ="foo")
@Table(name = "childfoo")
public class Childfoo implements Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = -8142203085486540150L;
    
    @Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "user_record_id")
    private Integer childfooId;

    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    @JoinColumn(name = "foo_id")
     @JsonProperty(access = JsonProperty.Access.WRITE_ONLY)
    private Foo foo;
    
    @Column(name="child_name")
     private String childName;

   }

I've created a repository for the Foo and child foo to be used in the controller to save the data.

Controller code to add the foo and childfoo:

Foo foo = new Foo();
foo.set...

   ChildFoo childFoo = new ChildFoo();
        childFoo.setChildName("abc");
        childFoo.setFoo(foo);

  childFoo.save(childFoo);

EDIT:

Now I'll need to get the childFoo using the someId and someName value . I tried using the join but was wondering if there is any effective way to write a query in ChildFooRepository/ Foo Repository to pass someId and someName.

I have this query in the childFoo and getting the error:

SELECT cf from schema.child_foo cf join schema.foo f"+""
            + " ON cf.foo_id = f.foo_id"+""
                    + " where f.some_id = :someid AND 
               f.somename= :somename

Shall I be adding this query in the Foo repository and not the child foo repository?

fladdimir · Accepted Answer · 2021-05-12T18:23:56.490

1

You need to make sure that both Foo and ChildFoo are persisted, and that the bidirectional association is synchronized (so when calling setFoo(foo) on the child you should also add childFoo to the corresponding collection of children on the parent).

So in your case you will probably also need to call save on the parent.

(see documentation samples on cascading operations and synchronizing bidirectional associations)

edited May 12 '21 at 18:23

answered May 12 '21 at 18:09

fladdimir

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What would be the jpa repository method I could use to get the childfoo using extraId and extraname(in foo) as input. Do I need to write a custom join query? I wrote the join query, but am getting error child_foo_id wasn't found on the resultset...I tried to use the query from above but am getting error saying missing from..I must be missing something here!! – user6090970 May 12 '21 at 19:34
please don't mix different questions into one, create a new one instead. but in this case, I'd probably read through the jpa repository documentation and/or existing stackoverflow posts first (e.g. you might have a look at this recently answered question also addressing a problem of querying by an attribute of related entities : https://stackoverflow.com/a/67494555/13156126 – fladdimir May 12 '21 at 19:49

One To Many Bidirectional relationship implementation postgres SpringBoot

1 Answers1