One to One Mapping using JPA, While inserting data it's throwing an Exception

Question

I am doing One to One Relationship using JSP. I understand that One To One means,One object is associated with one object only.I created two tables with One to One relationsip. Table POJO classes shown below.

ParentTable:

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;

private int num;

//bi-directional one-to-one association to Childtable
@OneToOne(mappedBy="parenttable")
private Childtable childtable;

ChildTable:

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;

private String email;

private String name;

//bi-directional one-to-one association to Parenttable
@OneToOne
@JoinColumn(name="id")
private Parenttable parenttable;

Is there any wrong while creating table with One To One relationship. If it's not I am trying to inserting data into table.While inserting data it's throwing Exception.

Insert.java

 public class Insert {
    public static void main(String[] args) {
 Parenttable parenttable = new Parenttable();

 Childtable childtable=new Childtable();

 parenttable.setNum(123);
 childtable.setName("prabha");
 childtable.setEmail("prabha@gmail.com");
 childtable.setParenttable(parenttable); 
 EntityManagerFactory emf = Persistence
            .createEntityManagerFactory("jpaCRUDApp");
    EntityManager em = emf.createEntityManager();
    try {
        EntityTransaction entr = em.getTransaction();
        entr.begin();
        em.persist(childtable);
        entr.commit();
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        em.close();
    }
    }
}

Exception is:

 Exception in thread "main" javax.persistence.PersistenceException: Exception [EclipseLink-28019] (Eclipse Persistence Services - 2.5.1.v20130918-f2b9fc5): org.eclipse.persistence.exceptions.EntityManagerSetupException
 Exception Description: Deployment of PersistenceUnit [jpaCRUDApp] failed. Close all factories for this PersistenceUnit.
 Internal Exception: Exception [EclipseLink-0] (Eclipse Persistence Services -    2.5.1.v20130918-f2b9fc5): org.eclipse.persistence.exceptions.IntegrityException

Descriptor Exceptions:

 Exception [EclipseLink-48] (Eclipse Persistence Services - 2.5.1.v20130918-f2b9fc5): org.eclipse.persistence.exceptions.DescriptorException
 Exception Description: Multiple writable mappings exist for the field [CHILDTABLE.ID].  Only one may be defined as writable, all others must be specified read-only.
 Mapping: org.eclipse.persistence.mappings.OneToOneMapping[parenttable]
 Descriptor: RelationalDescriptor(com.demo1.OneToOne.Childtable --> [DatabaseTable(CHILDTABLE)])    

Answer 1

Edit in parent table

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;

private int num;

//bi-directional one-to-one association to Childtable
@OneToOne(fetch = FetchType.LAZY, mappedBy = "parenttable", cascade = CascadeType.ALL)
private Childtable childtable;

Edit in child table

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;

private String email;

private String name;

//bi-directional one-to-one association to Parenttable

@OneToOne(fetch = FetchType.LAZY)
@PrimaryKeyJoinColumn
private Parenttable parenttable;