[jboss-user] [JBoss Seam] - Re: validation / exception handling patterns with EntityHome

[mbertelsen]

Is it possible to implement a hibernate validator with this functionality (run a query to determine uniqueness)?  It's not clear from looking at the hibernate validator docs how i would inject a persistence context to use.

BTW, I got the above strategy to work, but had to change a few things to get it to validate the unique property field itself.  It wasn't clear how to set up the view to validate the *entire* object.


  | @Name("clusterConfigUniqueValidator")
  | @Validator
  | @Transactional
  | public class ClusterConfigUniqueNameValidator implements javax.faces.validator.Validator, Serializable{
  | 	@In
  | 	EntityManager entityManager;
  | 	
  | 	@In EntityHome<ClusterConfig> clusterConfigHome;
  | 
  | 	public void validate(FacesContext facesContext, UIComponent component,
  | 			Object value) throws ValidatorException {
  | 		String name = (String) value;
  | 		ClusterConfig cc = clusterConfigHome.getInstance();
  | 		try {
  | 			ClusterConfig cc1 = (ClusterConfig) entityManager.createQuery("select cc from ClusterConfig cc where cc.name = :name")
  | 				.setParameter("name", name).getSingleResult();
  | 			if (cc1 != null && !cc1.getId().equals(cc.getId())) {
  | 				throw new ValidatorException(new FacesMessage("Name must be unique"));
  | 			}
  | 		} catch (NoResultException nre) {
  | 			// that's fine - this name is unique.
  | 		}
  | 	} 
  | 
  | }
  | 
  | And then on the edit page:
  | 
  | 		<s:decorate id="nameDecoration" template="layout/textField.xhtml">
  | 			<ui:define name="label">Name:</ui:define>
  | 				<h:inputText fieldIdBase="name" id="name" value="#{clusterConfig.name}" required="true">
  | 					<f:validator validatorId="clusterConfigUniqueValidator"/>
  | 					<s:validate/>
  | 				</h:inputText>
  | 		</s:decorate>
  | 
  | 

Also, what about dealing with SQLException when you delete something and violate a foreign key constraint?  Does anybody have a recommendation for how to avoid this gracefully?  Should I not display the delete link/button on my list page if it's referenced (which would require an extra query per entity listed)?  Write a custom exception handler in pages.xml to catch SQLException and a custom error page/handler that somehow parses the message?

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