Java tutorial
/* * Copyright (C) 2011 Citrix Systems, Inc. All rights reserved. * * Licensed 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 com.cloud.bridge.persist; import java.io.Serializable; import java.util.List; import org.hibernate.Query; import org.hibernate.Session; import com.cloud.bridge.util.QueryHelper; /** * @author Kelven Yang, John Zucker * Provide methods for getting, saving, deleting or updating state per session or, in a given session, returnin a List in * response to queryEntities for a particular instantation of the EntityDao generic class, as defined here. * Any instantation of EntityDao passes in the class for which it is instantiating. For example a new instance of SBucketDao * passes in com.cloud.bridge.model.SBucket as its clazz. * Instantiators, providing an Entity definition, are the classes * MHostDao, * MHostMountDao, * SAclDao, * SBucketDao, * SHostDao, * SMetaDao, * SObjectDao, * SObjectItemDao, * CloudStackSvcOfferingDao */ public class EntityDao<T> { private Class<?> clazz; private boolean isCloudStackSession = false; // Constructor to implement CloudStackSvcOffering: see class CloudStackSvcOfferingDao public EntityDao(Class<?> clazz) { this(clazz, false); } public EntityDao(Class<?> clazz, boolean isCloudStackSession) { this.clazz = clazz; this.isCloudStackSession = isCloudStackSession; // Note : beginTransaction can be called multiple times // "If a new underlying transaction is required, begin the transaction. Otherwise continue the new work in the // context of the existing underlying transaction." from the Hibernate spec PersistContext.beginTransaction(isCloudStackSession); } @SuppressWarnings("unchecked") public T get(Serializable id) { Session session = PersistContext.getSession(isCloudStackSession); return (T) session.get(clazz, id); } public T save(T entity) { Session session = PersistContext.getSession(isCloudStackSession); session.saveOrUpdate(entity); return entity; } public T update(T entity) { Session session = PersistContext.getSession(isCloudStackSession); session.saveOrUpdate(entity); return entity; } public void delete(T entity) { Session session = PersistContext.getSession(isCloudStackSession); session.delete(entity); } public T queryEntity(String hql, Object[] params) { Session session = PersistContext.getSession(isCloudStackSession); Query query = session.createQuery(hql); query.setMaxResults(1); QueryHelper.bindParameters(query, params); return (T) query.uniqueResult(); } public List<T> queryEntities(String hql, Object[] params) { Session session = PersistContext.getSession(isCloudStackSession); Query query = session.createQuery(hql); QueryHelper.bindParameters(query, params); return (List<T>) query.list(); } public List<T> queryEntities(String hql, int offset, int limit, Object[] params) { Session session = PersistContext.getSession(isCloudStackSession); Query query = session.createQuery(hql); QueryHelper.bindParameters(query, params); query.setFirstResult(offset); query.setMaxResults(limit); return (List<T>) query.list(); } public int executeUpdate(String hql, Object[] params) { Session session = PersistContext.getSession(isCloudStackSession); Query query = session.createQuery(hql); QueryHelper.bindParameters(query, params); return query.executeUpdate(); } }