hibernate中使用原生sql查询

hibernate使用hql查询有诸多不便，比如无法在from后面使用select子查询，（貌似可以解决但是挺麻烦）

所以这里记录下自己找到的一些写法

首先拿到session对象：

  |-  HibernateSessionFactory.getSession();

这个类是我找的一个工具类，下面会附上工具代码，直接丢里面用就好了

最后在执行sql的时候有些不同

要使用

session.createSQLQuery 而不是session.createQuery

返回一个list的集合：

|-  List list = session.createSQLQuery(sql.toString()).list();

注意： 

这里的list集合是Object类型，如果想要其返回指定的类型需要做一些变动

返回指定类型的list集合

List list = session.createSQLQuery(sql.toString())
.addScalar("name")
.addScalar("amount",Hibernate.DOUBLE)
.addScalar("sum",Hibernate.INTEGER)
.setResultTransformer(Transformers.aliasToBean(实体.class)).list();
如果你要返回的数据并不多的话，直接addScalar 添加字段的名称和类型进去 ，String类型的数据是不需要加入类型参数的，最后将你需要得到的实体类型加进去

(感谢贡献者！)

package com.ap.batch.util;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;

/**
* Configures and provides access to Hibernate sessions, tied to the
* current thread of execution. Follows the Thread Local Session
* pattern, see {@link http://hibernate.org/42.html }.
*/
public class HibernateSessionFactory {

/**
* Location of hibernate.cfg.xml file.
* Location should be on the classpath as Hibernate uses
* #resourceAsStream style lookup for its configuration file.
* The default classpath location of the hibernate config file is
* in the default package. Use #setConfigFile() to update
* the location of the configuration file for the current session.
*/
private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";
private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
private static Configuration configuration = new Configuration();
private static org.hibernate.SessionFactory sessionFactory;
private static String configFile = CONFIG_FILE_LOCATION;

public HibernateSessionFactory() {
}

/**
* Returns the ThreadLocal Session instance. Lazy initialize
* the <code>SessionFactory</code> if needed.
*
* @return Session
* @throws HibernateException
*/

public static Session getAnotherSession() throws HibernateException{
if (sessionFactory == null) {
rebuildSessionFactory();
}
return sessionFactory.openSession();

}

public static Session getSession() throws HibernateException {
Session session = (Session) threadLocal.get();

if (session == null || !session.isOpen()) {
if (sessionFactory == null) {
rebuildSessionFactory();
}
session = (sessionFactory != null) ? sessionFactory.openSession()
: null;
threadLocal.set(session);
}

return session;
}

/**
* Rebuild hibernate session factory
*
*/
public static void rebuildSessionFactory() {
try {
configuration.configure(configFile);
sessionFactory = configuration.buildSessionFactory();
} catch (Exception e) {
System.err
.println("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}

/**
* Close the single hibernate session instance.
*
* @throws HibernateException
*/
public static void closeSession() throws HibernateException {
Session session = (Session) threadLocal.get();
threadLocal.set(null);

if (session != null) {
session.close();
}
}

/**
* return session factory
*
*/
public static org.hibernate.SessionFactory getSessionFactory() {
return sessionFactory;
}

public static void setConfigFile(String configFile) {
HibernateSessionFactory.configFile = configFile;
sessionFactory = null;
}

/**
* return hibernate configuration
*
*/
public static Configuration getConfiguration() {
return configuration;
}
}