JPA insert parent and child entities in the same transaction

Question

I'm completely stuck in this matter, maybe someone can help.

I have two entities, Parent and Child. Test1Entity is the parent, Test1ChildEntity is the child. Great naming, of course. The database is Mysql, the JPA provider is Hibernate. Below are the definitions for the two entities:

@Table(name = "Test1", schema = "", catalog = "")
@Entity
public class Test1Entity {
    private int id;

    @Column(name = "id")
    @Id
    public int getId() {
        return id;
    }

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

    private String name;

    @Column(name = "name")
    @Basic
    public String getName() {
        return name;
    }

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

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Test1Entity that = (Test1Entity) o;

        if (id != that.id) return false;
        if (name != null ? !name.equals(that.name) : that.name != null) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = id;
        result = 31 * result + (name != null ? name.hashCode() : 0);
        return result;
    }

    private Collection<Test1ChildEntity> test1ChildrenById;

    @OneToMany(mappedBy = "test1ByParentId")
    public Collection<Test1ChildEntity> getTest1ChildrenById() {
        return test1ChildrenById;
    }

    public void setTest1ChildrenById(Collection<Test1ChildEntity> test1ChildrenById) {
        this.test1ChildrenById = test1ChildrenById;
    }

}


@Table(name = "Test1_Child", schema = "", catalog = "")
@Entity
public class Test1ChildEntity {
    private int id;

    @Column(name = "id")
    @Id
    public int getId() {
        return id;
    }

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

    private String name;

    @Column(name = "name")
    @Basic
    public String getName() {
        return name;
    }

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

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Test1ChildEntity that = (Test1ChildEntity) o;

        if (id != that.id) return false;
        if (name != null ? !name.equals(that.name) : that.name != null) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = id;
        result = 31 * result + (name != null ? name.hashCode() : 0);
        return result;
    }

    private Test1Entity test1ByParentId;

    @ManyToOne
    @JoinColumn(name = "parent_id")
    public Test1Entity getTest1ByParentId() {
        return test1ByParentId;
    }

    public void setTest1ByParentId(Test1Entity test1ByParentId) {
        this.test1ByParentId = test1ByParentId;
    }
}

The code trying to insert one parent with one child in the same transaction is below:

@Transactional
    public void createItWell(String parentName, String childName) {

        Test1Entity parent = new Test1Entity();

        parent.setName(parentName);

        Test1ChildEntity child = new Test1ChildEntity();

        child.setName(childName);
        child.setTest1ByParentId(parent);

        Set<Test1ChildEntity> mySet = new HashSet<>();

        mySet.add(child);
        parent.setTest1ChildrenById(mySet);

        this.entityManager.persist(parent);
        this.entityManager.persist(child);

    }

I get the following exception while trying to execute this code:

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`comwork`.`test1_child`, CONSTRAINT `test1_child_ibfk_1` FOREIGN KEY (`parent_id`) REFERENCES `Test1` (`id`))
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.Util.getInstance(Util.java:386)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1041)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4187)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4119)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2570)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2731)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2815)
    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2155)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2458)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2375)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2359)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:133)

Inserting other entities, stand-alone (no relations involved) works perfectly fine.

The two table definitions are:

CREATE TABLE `Test1` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(20) NOT NULL DEFAULT '',
  PRIMARY KEY (`id`),
  UNIQUE KEY `id` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

LOCK TABLES `Test1` WRITE;
/*!40000 ALTER TABLE `Test1` DISABLE KEYS */;

INSERT INTO `Test1` (`id`, `name`)
VALUES
    (6,'Parent');

/*!40000 ALTER TABLE `Test1` ENABLE KEYS */;
UNLOCK TABLES;


# Dump of table Test1_Child
# ------------------------------------------------------------

CREATE TABLE `Test1_Child` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `parent_id` int(11) unsigned NOT NULL,
  `name` varchar(20) NOT NULL DEFAULT '',
  PRIMARY KEY (`id`),
  KEY `parent_id` (`parent_id`),
  CONSTRAINT `test1_child_ibfk_1` FOREIGN KEY (`parent_id`) REFERENCES `Test1` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

I'm new to JPA, so sorry for what probably is a trivial question.

Thank you.

Answer 1

For whoever runs into this... The entity code was generated using Idea Intellij persistance generating tool.

Apparently the tool fails to annotate the @Id fields with @GeneratedValue, thus disabling id fetching after the first (parent) entity is inserted. This way the child entity was getting inserted with a 0 (obviously invalid) value for the foreign key field.

Just add the @GeneratedValue to the @Id annotated property and it works fine.

Answer 2

Try setting Cascade attribute on OneToMany relation:

@OneToMany(cascade = {CascadeType.ALL}, fetch = FetchType.LAZY)
private Collection<Test1ChildEntity> test1ChildrenById;