Update a table using JPA in Play Framework - jpa

Question

I'm trying to update a table using JPA
EntityManager em=JPA.em();
EntityTransaction entr = em.getTransaction();
try{
if(!entr.isActive())
entr.begin();
Tblrecordtypefields updateTblrecordtypes = em.find(Tblrecordtypefields.class,9);
updateTblrecordtypes.setFieldlabel("JPATest");
em.getTransaction().commit();
}finally
{
if(entr.isActive())
entr.rollback();
}
i'm getting the error
NullPointerException occured : null at
updateTblrecordtypes.setFieldlabel("JPATest");
What should i do.

Answer 1

I see some possible issues in there:
First, Play manages the transactions on it's own. A transaction is created at the beginning of the request and committed (rollback if exception) at the end. You are trying to force your way into it, that's not recommended. To manage the entity, just do an entity.save() to mark it as "to be saved" and don't do tht to ignore any changes.
Second, if you are using the Model class in Play (as you should) you can use the "find" and "findById" methods provided by this class. This is recommened, instead of using the EntityManager directly.
See the documentation for more information.
Basically, redo your code to follow the Play way, to avoid problems :)
EDIT: as a clarification, I'm not really answering your question on why you get the NPE, but I think that as you are forcing your way into the settings of the framework you might (maybe not!) be seeing unexpected artifacts that will dissapear once you fix your code to follow convention.
If after that you still have the error let us know :)

Answer 2

This means that there is no row with ID 9 in the database table mapped by the entity Tblrecordtypefields.
BTW: I find it very questionable to commit a transaction in a method which is not necessary the one that started the transaction.

Answer 3

I have changed my code as below
Tblrecordtypefields updateTblrecordtypeFields = Tblrecordtypefields.findById(9);
updateTblrecordtypeFields.setFieldlabel("Test");
validation.valid(updateTblrecordtypeFields);
if(validation.hasErrors())
{
updateTblrecordtypeFields.refresh();
}
else
{
updateTblrecordtypeFields.save();
}
in my model class
public void setFieldlabel(String fieldlabel) {
this.fieldlabel = fieldlabel;
}
Works Fine.....