hibernate系列三:hibernate工具类及使用

在项目开发过程中，通常使用工具类来管理SessionFactory和Session，代码如下所示。

package com.obtk.utils;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
	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 = "/hibernate.cfg.xml";

	static {
    	try {
			configuration.configure(configFile);
			sessionFactory = configuration.buildSessionFactory();
		} catch (Exception e) {
			System.err
					.println("%%%% Error Creating SessionFactory %%%%");
			e.printStackTrace();
		}
    }
    private HibernateUtil() {
    }
	
    //获得session对象
    public static Session getSession() throws HibernateException {
        Session session = (Session) threadLocal.get();

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

        return session;
    }

    //重新建立session工厂
	public static void rebuildSessionFactory() {
		try {
			configuration.configure(configFile);
			sessionFactory = configuration.buildSessionFactory();
		} catch (Exception e) {
			System.err
					.println("%%%% Error Creating SessionFactory %%%%");
			e.printStackTrace();
		}
	}

	//关闭session
    public static void closeSession() throws HibernateException {
        Session session = (Session) threadLocal.get();
        threadLocal.set(null);

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

	public static SessionFactory getSessionFactory() {
		return sessionFactory;
	}

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

	public static Configuration getConfiguration() {
		return configuration;
	}

}

==========================================

用hibernateUtil工具类改造前面的程序如下：

package com.obtk.test;

import java.util.List;

import org.hibernate.HibernateException;
import org.hibernate.Query;
import org.hibernate.Session;

import com.obtk.entitys.UserEntity;
import com.obtk.utils.HibernateUtil;

public class TestHql01 {
	public static void main(String[] args) {
		Session session=null;
		String hqlSql="from UserEntity";
		try {
			//获得数据库链接
			session=HibernateUtil.getSession();
			//获得一个查询接口
			Query qy=session.createQuery(hqlSql);
			//得到结果
			List<UserEntity> userList=qy.list();
			for(UserEntity user : userList){
				System.out.println(user.getUserName()+","+user.getEmail());
			}
		} catch (HibernateException e) {
			e.printStackTrace();
		}finally{
			HibernateUtil.closeSession();
		}
	}
}