Question

I’m new to JPA and I’m trying some getting started example projects. I tried GraniteDS sample project (“Hello, World” app) and I found a method hello that updates or inserts java bean. It looks somehow bad for me but on other hand I’m not sure how it should look nicer.

UPDATE
I don’t like that Query must throw an exception to know that no results with Welcome entities exist. Is there any way to check if there any records in elegant way?

    package info.alekna.project.services;

import java.util.List;
import java.util.Date;
import java.text.SimpleDateFormat;

import javax.persistence.Query;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.NoResultException;

import org.granite.tide.data.DataEnabled;
import org.granite.tide.data.DataEnabled.PublishMode;


import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import info.alekna.project.entities.Welcome;


@Service
@DataEnabled(topic="welcomeTopic", publish=PublishMode.ON_SUCCESS)
public class WelcomeServiceImpl implements WelcomeService {

    @PersistenceContext
    private EntityManager entityManager;


    @Transactional
    public Welcome hello(String name) {
        if (name == null || name.trim().length() == 0)
            throw new RuntimeException("Name cannot be null or empty");

        SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss");
        Welcome welcome = null;
        try {
            Query q = entityManager.createQuery("select w from Welcome w where w.name = :name");
            q.setParameter("name", name);
            welcome = (Welcome)q.getSingleResult();
            welcome.setMessage("Welcome " + name + " (" + sdf.format(new Date()) + ")");
        }
        catch (NoResultException e) {
            welcome = new Welcome();
            welcome.setName(name);
            welcome.setMessage("Welcome " + name + " (" + sdf.format(new Date()) + ")");
            entityManager.persist(welcome);
        }
        return welcome;
    }


    @Transactional(readOnly=true)
    public List<Welcome> findAll() {
        return entityManager.createQuery("select w from Welcome w order by w.name", Welcome.class).getResultList();
    }
}

Answer 1

(Answering the question in the comments)
You can always use q.getResultList() and check the size of the list. The problem with doing this is that it causes a full run on the table, and if this is not needed, it should be avoided.

It is kind of logical to throw NoResultException if you explicitly call getSingleResult since it IS an exceptional state 🙂