Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, * software distributed under the License is distributed on an * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * KIND, either express or implied. See the License for the * specific language governing permissions and limitations * under the License. */ package org.apache.cxf.fediz.service.idp.service.jpa; import java.util.List; import javax.persistence.EntityManager; import javax.persistence.PersistenceContext; import javax.persistence.criteria.CriteriaBuilder; import javax.persistence.criteria.CriteriaQuery; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.ApplicationListener; import org.springframework.context.event.ContextRefreshedEvent; import org.springframework.stereotype.Component; @Component public class DBInitApplicationListener implements ApplicationListener<ContextRefreshedEvent> { private static final Logger LOG = LoggerFactory.getLogger(DBInitApplicationListener.class); private EntityManager em; @Autowired private List<DBLoader> dbloader; @PersistenceContext public void setEntityManager(EntityManager entityManager) { this.em = entityManager; } @Override public void onApplicationEvent(ContextRefreshedEvent arg0) { if (!isDBEmpty()) { LOG.info("Inital DB already loaded"); return; } LOG.debug("Loading inital DB data..."); for (DBLoader loader : this.dbloader) { loader.load(); LOG.info("Inital DB data loaded for " + loader.getName()); } } protected boolean isDBEmpty() { CriteriaBuilder cb = em.getCriteriaBuilder(); CriteriaQuery<Long> cq = cb.createQuery(Long.class); cq.select(cb.count(cq.from(ClaimEntity.class))); return em.createQuery(cq).getSingleResult() == 0; } }