JPA -- Using the one-to-one dependency relationship on insertion - jpa

Question

I have 2 entity classes with one-to-one dependencies on their primary keys:
The primary table:
#Entity
#Table(name = "tablePrimary")
#XmlRootElement
//...
public class TablePrimary implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Basic(optional = false)
#Column(name = "id")
private Integer id;
#Basic(optional = false)
#Column(name = "code")
private String code;
// set the dependency of table2 to this class
#OneToOne(cascade = CascadeType.ALL)
#PrimaryKeyJoinColumn
private Table2 table2inst;
// ...
} // end of class TablePrimary
The dependent table:
#Entity
#Table(name = "table2")
#XmlRootElement
//...
public class Table2 implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#Basic(optional = false)
#Column(name = "id")
private Integer id;
#Basic(optional = false)
#Column(name = "name")
private String name;
#MapsId
#OneToOne(mappedBy = "table2inst")
#JoinColumn(name = "id")
private TablePrimary tablePrimaryInst;
//...
} // end of class Table2
Whenever there is a row with say, id==55 in TablePrimary, there is
a row with the same id==55 in Table2 and vice-versa.
So in essence, these two tables are one table in logical level-- split into 2 physical tables for practicality.
When i'm inserting a row into the "logical" table,
i first am inserting to TablePrimary-- the primary table in the relationship,
getting the value of id==55 field of this new row i just inserted and inserting a row to
Table2 with that id value.
As part of this, i'm checking, just in case,
whether a row with id==55 is already in Table2.
Is there a better way of doing this?
Does JPA have a feature to make these two insertions to these two physical tables
by using the 1-1 dependency I configured on them-- without me having to do it "manually" in the code? Or a control feature on the id fields of the tables I set the dependency on?
If there is-- how is done? how does it handle the key value collision in the dependent table-- Table2?
A similar thing will come up on deletion. However, i'm not there yet, and might figure out out of this.
TIA.

Answer 1

You can take advantage of JPA cascading. You will have to define a cascade on the owning side (the one with the join column). If you have set the owning side of the relationship and persist the owning side, the inverse side will be persisted as well:
TablePrimary tp = new TablePrimary();
Table2 t2 = new Table2();
t2.setTablePrimaryInst(tp);
entityManager.persist(t2);
The 'mappedBy' element is supposed to be placed on the inverse side. You entities could look like this:
public class Table2 ...
#OneToOne(cascade=CascadeType.ALL)
#JoinColumn(name = "tp_id")
private TablePrimary tablePrimary;
public class TablePrimary...
#OneToOne(mappedBy="tablePrimary")
private Table2 table2;