Composite foreign key JPA TypeMismatchException - jpa

Question

I've explained my scenario through simple Parent Child tables.
My composite primary key is also a composite foreign key referencing Parent table.
create table parent(
code varchar(10) not null,
id int not null,
parentcol varchar(10),
primary key(code,id)
);
create table child(
code varchar(10) not null,
id int not null,
childcol varchar(10) not null,
primary key(code, id),
foreign key(code, id) references parent(code,id)
);
Entities created (this is through Eclipse JPA plugin)
#Entity
#Table(name="parent")
#NamedQuery(name="Parent.findAll", query="SELECT p FROM Parent p")
public class Parent implements Serializable {
private static final long serialVersionUID = 1L;
#EmbeddedId
private ParentPK id;
#Column(length=10)
private String parentcol;
//bi-directional one-to-one association to Child
#OneToOne(mappedBy="parent")
private Child child;
public Parent() {
}
/* getters and setters */
}
#Embeddable
public class ParentPK implements Serializable {
//default serial version id, required for serializable classes.
private static final long serialVersionUID = 1L;
#Column(unique=true, nullable=false, length=10)
private String code;
#Column(unique=true, nullable=false)
private int id;
/* getters and setters */
/** Overridden equals and hashcode **/
}
#Entity
#Table(name="child")
#NamedQuery(name="Child.findAll", query="SELECT c FROM Child c")
public class Child implements Serializable {
private static final long serialVersionUID = 1L;
#EmbeddedId
private ChildPK id;
#Column(nullable=false, length=10)
private String childcol;
//bi-directional one-to-one association to Parent
#OneToOne
#JoinColumns({
#JoinColumn(name="code", referencedColumnName="code", nullable=false, insertable=false, updatable=false),
#JoinColumn(name="id", referencedColumnName="id", nullable=false, insertable=false, updatable=false)
})
private Parent parent;
/* getters and setters */
}
#Embeddable
public class ChildPK implements Serializable {
//default serial version id, required for serializable classes.
private static final long serialVersionUID = 1L;
#Column(insertable=false, updatable=false, unique=true, nullable=false, length=10)
private String code;
#Column(insertable=false, updatable=false, unique=true, nullable=false)
private int id;
/* overridden equals and hashcode */
I am using Spring data to save my entities as below. Parent table consist of a record with code as "code" and Id as 1.
Child child = new Child();
ChildPK childPK = new ChildPK();
childPK.setCode("code");
childPK.setId(1);
child.setId(childPK);
child.setChildcol("child1");
childRepository.save(child);
It succeeds with the 1st run when it has to insert a new record. But the issue is on the 2nd run when it has to update let's say with,
child.setChildcol("child2");
I face an error
HHH000327: Error performing load command : org.hibernate.TypeMismatchException: Provided id of the wrong type for class com.xebia.eTechLog.entities.Parent. Expected: class com.xebia.eTechLog.entities.ParentPK, got class com.xebia.eTechLog.entities.ChildPK
In case I try to give a reference of ParentPk in the Child table as
#Entity
#Table(name="child")
#NamedQuery(name="Child.findAll", query="SELECT c FROM Child c")
public class Child implements Serializable {
private static final long serialVersionUID = 1L;
#EmbeddedId
private ParentPK id;
#Column(nullable=false, length=10)
private String childcol;
//bi-directional one-to-one association to Parent
#OneToOne
#JoinColumns({
#JoinColumn(name="code", referencedColumnName="code", nullable=false, insertable=false, updatable=false),
#JoinColumn(name="id", referencedColumnName="id", nullable=false, insertable=false, updatable=false)
})
private Parent parent;
It does work, but it won't in case there are more fields in the Parent class, which is my real scenario.

Answer 1

You should use a derived identity. Which means you should indicate that the child's reference to its parent maps the child's ID (with a #MapsId annotation):
#Entity
public class Child implements Serializable {
#EmbeddedId
private ChildPK id;
#Column(nullable=false, length=10)
private String childcol;
#OneToOne
#MapsId // <<< NB
#JoinColumns({
#JoinColumn(name="code", referencedColumnName="code"),
#JoinColumn(name="id", referencedColumnName="id")
})
private Parent parent;
...
}
Derived identities are discussed in the JPA 2.1 spec in section 2.4.1.