How to handle validator and exception gracefully in ManyToOne relation?

[alartin]

Hi all,

A big advantage of seam is to handle validator and exception. For example, you can check a Person's email is not null or empty or valid and get an error message when submit it or just lose the focus (ajax). It can be handled easily if this is a field with simple type like String. My scenario is I have three entities: person, employment and company. Employment contains a person, a company and a period.
So person and employment is a OneToMany relation, the same is true for company and employment. Of course, employment must contain person and company with notnull annotation. When I test to persist a employment without a person or a company, Seam will direct me to a debug page with javax.persistence.PersistenceException: org.hibernate.PropertyValueException: not-null property references a null or transient value exception which is not graceful like email validation. I hope I can get a error message like 'Employment must contain a person and a company in the same page of submit button. How do I achieve this? I've read seam exception document and think catch org.hibernate.PropertyValueException or PersistenceException is not what I want. Thanks a lot.

[serkan.s.eskici.online.nl]

There are many ways to do this:

1. page specific solution: put your code between try-catch, catch the exception and create a FacesMessage. Or bind your JSF componont to a validator e.g. a method in your bean and validate it there before doing a CRUD.


2. general solution: configure the exception in your pages.xml and set a general message inside it (you must disable debug mode in Seam & Facelets to see this working). Or you can write an @Observer(with the name of the exception) and create a FacesMessage(s) inside it.

Hope this helps.