Hibernate object operations and hql

Today, we performed crud for the simplest hibernate object operation.

However, instead of using hibernate independently, it uses hibernate hosted by spring. In addition, Hibernate itself is not needed, but the encapsulated class hibernatetemplate.

Simply put, there are two aspects.

I. Object

This is quite familiar and has a difference: It inherits a class of hibernatedaosupport (usually implements an interface) and waits for spring container injection,

<Bean id = "idaotoolservice" class = "com. SMS. idao. impl. daotoolserviceimpl"> <! -- The property name must be the same as that of ref ???? --> <Property name = "sessionfactory"> <ref bean = "sessionfactory"/> </property> </bean>

In fact, I still don't understand why sessionfactory is injected. However, the source code explains everything.

You can clearly find that when daotoolserviceimpl extends hibernatedaosupport implements idaotoolservice,

It has

private HibernateTemplate hibernateTemplate;

And Get Set methods and constructor methods to provide spring injection.

/* * Copyright 2002-2008 the original author or authors. * * 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 org.springframework.orm.hibernate3.support;import org.hibernate.HibernateException;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.springframework.dao.DataAccessException;import org.springframework.dao.DataAccessResourceFailureException;import org.springframework.dao.support.DaoSupport;import org.springframework.orm.hibernate3.HibernateTemplate;import org.springframework.orm.hibernate3.SessionFactoryUtils;/** * Convenient super class for Hibernate-based data access objects. * * <p>Requires a {@link org.hibernate.SessionFactory} to be set, providing a * {@link org.springframework.orm.hibernate3.HibernateTemplate} based on it to * subclasses through the {@link #getHibernateTemplate()} method. * Can alternatively be initialized directly with a HibernateTemplate, * in order to reuse the latter's settings such as the SessionFactory, * exception translator, flush mode, etc. * * <p>This base class is mainly intended for HibernateTemplate usage but can * also be used when working with a Hibernate Session directly, for example * when relying on transactional Sessions. Convenience {@link #getSession} * and {@link #releaseSession} methods are provided for that usage style. * * <p>This class will create its own HibernateTemplate instance if a SessionFactory * is passed in. The "allowCreate" flag on that HibernateTemplate will be "true" * by default. A custom HibernateTemplate instance can be used through overriding * {@link #createHibernateTemplate}. * * @author Juergen Hoeller * @since 1.2 * @see #setSessionFactory * @see #getHibernateTemplate * @see org.springframework.orm.hibernate3.HibernateTemplate */public abstract class HibernateDaoSupport extends DaoSupport {private HibernateTemplate hibernateTemplate;/** * Set the Hibernate SessionFactory to be used by this DAO. * Will automatically create a HibernateTemplate for the given SessionFactory. * @see #createHibernateTemplate * @see #setHibernateTemplate */public final void setSessionFactory(SessionFactory sessionFactory) {if (this.hibernateTemplate == null || sessionFactory != this.hibernateTemplate.getSessionFactory()) {this.hibernateTemplate = createHibernateTemplate(sessionFactory);}}/** * Create a HibernateTemplate for the given SessionFactory. * Only invoked if populating the DAO with a SessionFactory reference! * <p>Can be overridden in subclasses to provide a HibernateTemplate instance * with different configuration, or a custom HibernateTemplate subclass. * @param sessionFactory the Hibernate SessionFactory to create a HibernateTemplate for * @return the new HibernateTemplate instance * @see #setSessionFactory */protected HibernateTemplate createHibernateTemplate(SessionFactory sessionFactory) {return new HibernateTemplate(sessionFactory);}/** * Return the Hibernate SessionFactory used by this DAO. */public final SessionFactory getSessionFactory() {return (this.hibernateTemplate != null ? this.hibernateTemplate.getSessionFactory() : null);}/** * Set the HibernateTemplate for this DAO explicitly, * as an alternative to specifying a SessionFactory. * @see #setSessionFactory */public final void setHibernateTemplate(HibernateTemplate hibernateTemplate) {this.hibernateTemplate = hibernateTemplate;}/** * Return the HibernateTemplate for this DAO, * pre-initialized with the SessionFactory or set explicitly. * <p><b>Note: The returned HibernateTemplate is a shared instance.</b> * You may introspect its configuration, but not modify the configuration * (other than from within an {@link #initDao} implementation). * Consider creating a custom HibernateTemplate instance via * <code>new HibernateTemplate(getSessionFactory())</code>, in which * case you're allowed to customize the settings on the resulting instance. */public final HibernateTemplate getHibernateTemplate() {  return this.hibernateTemplate;}protected final void checkDaoConfig() {if (this.hibernateTemplate == null) {throw new IllegalArgumentException("'sessionFactory' or 'hibernateTemplate' is required");}}/** * Obtain a Hibernate Session, either from the current transaction or * a new one. The latter is only allowed if the * {@link org.springframework.orm.hibernate3.HibernateTemplate#setAllowCreate "allowCreate"} * setting of this bean's {@link #setHibernateTemplate HibernateTemplate} is "true". * <p><b>Note that this is not meant to be invoked from HibernateTemplate code * but rather just in plain Hibernate code.</b> Either rely on a thread-bound * Session or use it in combination with {@link #releaseSession}. * <p>In general, it is recommended to use HibernateTemplate, either with * the provided convenience operations or with a custom HibernateCallback * that provides you with a Session to work on. HibernateTemplate will care * for all resource management and for proper exception conversion. * @return the Hibernate Session * @throws DataAccessResourceFailureException if the Session couldn't be created * @throws IllegalStateException if no thread-bound Session found and allowCreate=false * @see org.springframework.orm.hibernate3.SessionFactoryUtils#getSession(SessionFactory, boolean) */protected final Session getSession()    throws DataAccessResourceFailureException, IllegalStateException {return getSession(this.hibernateTemplate.isAllowCreate());}/** * Obtain a Hibernate Session, either from the current transaction or * a new one. The latter is only allowed if "allowCreate" is true. * <p><b>Note that this is not meant to be invoked from HibernateTemplate code * but rather just in plain Hibernate code.</b> Either rely on a thread-bound * Session or use it in combination with {@link #releaseSession}. * <p>In general, it is recommended to use * {@link #getHibernateTemplate() HibernateTemplate}, either with * the provided convenience operations or with a custom * {@link org.springframework.orm.hibernate3.HibernateCallback} that * provides you with a Session to work on. HibernateTemplate will care * for all resource management and for proper exception conversion. * @param allowCreate if a non-transactional Session should be created when no * transactional Session can be found for the current thread * @return the Hibernate Session * @throws DataAccessResourceFailureException if the Session couldn't be created * @throws IllegalStateException if no thread-bound Session found and allowCreate=false * @see org.springframework.orm.hibernate3.SessionFactoryUtils#getSession(SessionFactory, boolean) */protected final Session getSession(boolean allowCreate)    throws DataAccessResourceFailureException, IllegalStateException {return (!allowCreate ?    SessionFactoryUtils.getSession(getSessionFactory(), false) :SessionFactoryUtils.getSession(getSessionFactory(),this.hibernateTemplate.getEntityInterceptor(),this.hibernateTemplate.getJdbcExceptionTranslator()));}/** * Convert the given HibernateException to an appropriate exception from the * <code>org.springframework.dao</code> hierarchy. Will automatically detect * wrapped SQLExceptions and convert them accordingly. * <p>Delegates to the * {@link org.springframework.orm.hibernate3.HibernateTemplate#convertHibernateAccessException} * method of this DAO's HibernateTemplate. * <p>Typically used in plain Hibernate code, in combination with * {@link #getSession} and {@link #releaseSession}. * @param ex HibernateException that occured * @return the corresponding DataAccessException instance * @see org.springframework.orm.hibernate3.SessionFactoryUtils#convertHibernateAccessException */protected final DataAccessException convertHibernateAccessException(HibernateException ex) {return this.hibernateTemplate.convertHibernateAccessException(ex);}/** * Close the given Hibernate Session, created via this DAO's SessionFactory, * if it isn't bound to the thread (i.e. isn't a transactional Session). * <p>Typically used in plain Hibernate code, in combination with * {@link #getSession} and {@link #convertHibernateAccessException}. * @param session the Session to close * @see org.springframework.orm.hibernate3.SessionFactoryUtils#releaseSession */protected final void releaseSession(Session session) {SessionFactoryUtils.releaseSession(session, getSessionFactory());}}

Of course, you can continue to look at the source code of the hibernatetemplate class ~ But that makes no sense to me now ~.

So far, why does spring inherit the hibernatedaosupport class and how to inject sessionfactory injection?

Ii. hql

The methods used by hibernatedaosupport to operate databases are basically the above, and hql,

Object operations have great limitations ~~ Hql is very convenient, but the syntax is different from that of common SQL.

//-------------------------------------------------------------------------// Convenience finder methods for HQL strings//-------------------------------------------------------------------------public List find(String queryString) throws DataAccessException {return find(queryString, (Object[]) null);}

It's just today ~