刚学的Hibernate求解session的关闭问题

Question

[code="java"]package com.pb.hibernate.util;

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

public class HibernateUtil {
private static Session session;

private HibernateUtil(){}

static{
    buildSession();
}

private static void buildSession(){
    Configuration config=new Configuration().configure();
    SessionFactory sf=config.buildSessionFactory();
    session=sf.openSession();
}

public static Session getSession(){
    if (session==null) {
        buildSession();
    }
    return session;
}

public static void closeSession(){
    if (session!=null) {
        session.close();
    }
}

}[/code] 这是我们老师写的代码，一个Hibernate的工具类，23行好像有问题，session关闭后不为空，就不会执行buildSession()这个方法，然后就一直报session is closed，求修正

Answer 1

建议使用ThreadLocal 来编写hibernate的Session初始化 这也是hibernate官方建议的
[code="java"]
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateFactory {
private static Configuration cfg;
private static SessionFactory sf;
private static ThreadLocal th = new ThreadLocal();

static {
    cfg = new Configuration();
    cfg.configure();
    sf = cfg.buildSessionFactory();
}

public static Session getSession() {
    Session session = th.get();
    if (session == null) {
        session = sf.openSession();
        th.set(session);
    }
    return session;
}

public static void closeSession() {
    Session session = th.get();
    if (session != null) {
        session.close();
        th.set(null);
    }
}

}
[/code]