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

i doing 1 one relationship using jsp. understand 1 one means,one object associated 1 object only.i created 2 tables 1 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 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 parenttable @onetoone @joincolumn(name="id") private parenttable parenttable; 

is there wrong while creating table 1 one relationship. if it's not trying inserting data 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();     } {         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 factories 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 field [childtable.id].  1 may defined writable, others must specified read-only.  mapping: org.eclipse.persistence.mappings.onetoonemapping[parenttable]  descriptor: relationaldescriptor(com.demo1.onetoone.childtable --> [databasetable(childtable)])     

edit in parent table

@id @generatedvalue(strategy=generationtype.identity) private int id;  private int num;  //bi-directional one-to-one association 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 parenttable  @onetoone(fetch = fetchtype.lazy) @primarykeyjoincolumn private parenttable parenttable;