`JPAQuery.first()` raised `NoResultException` when no result found

[greenlaw110]

When using JPAQuery.first() in the case where no result in the database matches the query criteria, it will raise an exception javax.persistence.NoResultException, here is the error stack trace:

javax.persistence.NoResultException: No entity found for query
	at org.hibernate.jpa.internal.QueryImpl.getSingleResult(QueryImpl.java:532)
	at act.db.jpa.JPAQuery.first(JPAQuery.java:141)
	at com.wykj.mcs.controllers.Application.test(Application.java:64)
	at com.wykj.mcs.controllers.ApplicationMethodAccess.invoke(Unknown Source)
	at act.handler.builtin.controller.impl.ReflectedHandlerInvoker.invoke(ReflectedHandlerInvoker.java:815)
	at act.handler.builtin.controller.impl.ReflectedHandlerInvoker.handle(ReflectedHandlerInvoker.java:480)
	at act.handler.builtin.controller.ControllerAction.handle(ControllerAction.java:48)
	at act.handler.builtin.controller.RequestHandlerProxy._handle(RequestHandlerProxy.java:517)
	at act.handler.builtin.controller.RequestHandlerProxy.handle(RequestHandlerProxy.java:203)
	at act.app.ActionContext.proceedWithHandler(ActionContext.java:1050)
	at act.route.Router$ContextualHandler.handle(Router.java:1596)
	at act.xio.NetworkHandler$3.run(NetworkHandler.java:159)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:745)

[greenlaw110]

This is actually a standard behavior of JPA query, though a lot of people don't appreciate this behavior. See the discussion at https://stackoverflow.com/questions/2002993/.

I am actually on the side against this JPA behavior and I am happy to change the behavior into return null value when data not found.

The concern is database actually allows NULL value and semantically when query for a record on a single column (of type say varchar), it might happen to be NULL, and in which case it will return just null to indicate the record is there, but the column value is null. However this doesn't makes big deal in our case and our JPAQuery.first() shall always return a full fleshed bean instance, instead of a single column value.