Spring HibernateTemplate详解

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1：get/load存取单条数据

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public Teacher getTeacherById(Long id) {
return (Teacher)this.hibernateTemplate.get(Teacher.class, id);
}
public Teacher getTeacherById(Long id) {
return (Teacher)this.hibernateTemplate.load(Teacher.class, id);
}

                public Teacher getTeacherById(Long id) {            return (Teacher)this.hibernateTemplate.get(Teacher.class, id);        }        public Teacher getTeacherById(Long id) {            return (Teacher)this.hibernateTemplate.load(Teacher.class, id);        }

2：find/iterate查询操作

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public Iterator getTeachersByAge(int age) {
Iterator iterator = null;
//使用find方法
List list = (List)this.hibernateTemplate().find(“from Teacher t where t.age>?”, new Integer(age));
iterator = list.iterator();
//使用iterator方法
iterator = this.hibernateTemplate().iterate(“from Teacher t where t.age>?”, new Integer(age));
return iterator;
}

               public Iterator getTeachersByAge(int age) {            Iterator iterator = null;            //使用find方法            List list = (List)this.hibernateTemplate().find("from Teacher t where t.age>?", new Integer(age));            iterator = list.iterator();            //使用iterator方法            iterator = this.hibernateTemplate().iterate("from Teacher t where t.age>?", new Integer(age));            return iterator;        }

find和iterato的区别主要是iterate采用了N+1次查询，对于大批量查询，比如查询10000条记录，那么iterate就要执行10000+1次查询，find和iterate应根据具体的实际

情况来使用，对于频繁的写操作对象，应使用find查询，而对于一些只读的数据对象，应使用iterate操作，因为iterate操作使用了hibernate的缓存机制

3：save/update/saveOrUpdate/delete 保存/更新/删除操作

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public void save(Teacher teacher) {
this.hibernateTemplate.save(teacher);
}

        public void save(Teacher teacher) {        this.hibernateTemplate.save(teacher);    }

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public void update(Teacher teacher) {
this.hibernateTemplate.update(teacher);
}

        public void update(Teacher teacher) {        this.hibernateTemplate.update(teacher);    }

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public void update(Teacher teacher) {
this.hibernateTemplate.saveOrUpdate(teacher);
}

       public void update(Teacher teacher) {        this.hibernateTemplate.saveOrUpdate(teacher);    }

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public void update(Teacher teacher) {
this.hibernateTemplate.delete(teacher);
}

        public void update(Teacher teacher) {        this.hibernateTemplate.delete(teacher);    }

4：bulkUpdate批量删除或者更新

bulkUpdate提供了批量删除和更新，直接转换为相应的update/delete SQL进行批量删除和更新

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public void batchDelete(String name, int age) {
this.hibernateTemplate.bulkUpdate(“delete Teacher where name=? and age = ?”, new Object[]{name, age});
}

        public void batchDelete(String name, int age) {        this.hibernateTemplate.bulkUpdate("delete Teacher where name=? and age = ?", new Object[]{name, age});    }

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public void batchDelete(String name, String newName) {
this.hibernateTemplate.bulkUpdate(“update Teacher set name=? where name=?”, new Object[]{newName, name});
}

        public void batchDelete(String name, String newName) {        this.hibernateTemplate.bulkUpdate("update Teacher set name=? where name=?", new Object[]{newName, name});    }

此时要注意的一个问题是，使用bulkUpdate操作，必须手工清除相关对象在Hibernate中的缓存(包括一级缓存和二级缓存)

5：execute核心方法

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public Object execute(HibernateCallBack action, boolean exposeNativeSession) throws DataAccessException {
//获取一个Session
Session session = getSession();
//当前session是否在事务中
boolean existingTransaction = SessionFactoryUtils.isSessionTransactional(session, getSessionFactory());
FlushMode previousFlushMode = null;
try {
previousFlushMode = applyFlushMode(session, existingTransaction); //应用flush模式
enableFilters(session);
//暴露给action的session
Session sessionToExpose = (exposeNativeSession? session: createSessionProxy(session));
//执行action
Object result = action.doInHibernate(sessionToExpose);
flushIfNecessary(session, existingTransaction);
return result;
} catch(HibernateException ex) {
throw convertHibernateAccessException(ex);
} catch(SQLException ex) {
throw convertJdbcAccessException(ex);
} catch(RuntimeException ex) {
throw ex;
} finally {
//如果session在事务中，则不关闭session
if(existingTransaction) {
disableFilters(session);
if(previousFlushMode != null) {
session.setFlushMode(previousFlushMode);
}
} else {
//释放session
SessionFactoryUtils.releaseSession(session, getSessionFactory());
}
}
}

public Object execute(HibernateCallBack action, boolean exposeNativeSession) throws DataAccessException {        //获取一个Session        Session session = getSession();        //当前session是否在事务中        boolean existingTransaction = SessionFactoryUtils.isSessionTransactional(session, getSessionFactory());        FlushMode previousFlushMode = null;        try {            previousFlushMode = applyFlushMode(session, existingTransaction); //应用flush模式            enableFilters(session);            //暴露给action的session            Session sessionToExpose = (exposeNativeSession? session: createSessionProxy(session));            //执行action            Object result = action.doInHibernate(sessionToExpose);            flushIfNecessary(session, existingTransaction);            return result;        } catch(HibernateException ex) {            throw convertHibernateAccessException(ex);        } catch(SQLException ex) {            throw convertJdbcAccessException(ex);        } catch(RuntimeException ex) {            throw ex;        } finally {            //如果session在事务中，则不关闭session            if(existingTransaction) {                disableFilters(session);                if(previousFlushMode != null) {                    session.setFlushMode(previousFlushMode);                }            } else {                //释放session                SessionFactoryUtils.releaseSession(session, getSessionFactory());            }        }    }

*HibernateCallBack，一般用来实现特定的业务逻辑

*exposeNativeSession：是一个布尔值，要暴露给HibernateCallBack实际的session对象，而不是一个代理过的对象

6：一般情况下，只有HIberateTemplate提供的方法不能满足要求时才使用execute方法，它的使用情况如下所示，

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public void createDatabaseSchema() throws DataAccessException {
HibernateTemplate hibernateTemplate = new HibernateTemplate(this.sessionFactory);
//调用HibernateTempalte的execute方法
hibernateTemplate.execute(new HibernateCallback() {
public Object doInHibernate(Session session) throws HibernateException, SQLException { //实现HibernateCallback的doInHibernate方法
//具体实现
Connection conn = session.connection();
final Dialect dialect = Dialect.getDialect(configuration.getProperties);
String[] sql = configuration.generateSchemaCreationScript(dialect);
executeSchemaScript(conn, sql);
}
});
}

        public void createDatabaseSchema() throws DataAccessException {        HibernateTemplate hibernateTemplate = new HibernateTemplate(this.sessionFactory);        //调用HibernateTempalte的execute方法        hibernateTemplate.execute(new HibernateCallback() {            public Object doInHibernate(Session session) throws HibernateException, SQLException {  //实现HibernateCallback的doInHibernate方法                //具体实现                Connection conn = session.connection();                final Dialect dialect = Dialect.getDialect(configuration.getProperties);                String[] sql = configuration.generateSchemaCreationScript(dialect);                executeSchemaScript(conn, sql);            }        });    }

使用execute方法的重点是实现HibernateCallback的doInHibernate方法，它会传递一个Session实例，可以使用此Session实例操作数据库，由此看出execute方法的好处是应用程序不用关心session的创建和释放，只需要处理关心的业务逻辑即可。

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