Hibernate在java中的CRUD

package cn.itcast.hibernate;

import java.io.Serializable;

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

public final class HibernateUtil {
private static SessionFactory sessionFactory;
private static ThreadLocal session = new ThreadLocal();

private HibernateUtil() {
}

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

public static Session getThreadLocalSession() {
Session s = (Session) session.get();
if (s == null) {
s = getSession();
session.set(s);
}
return s;
}

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

public static SessionFactory getSessionFactory() {
return sessionFactory;
}

public static Session getSession() {
return sessionFactory.openSession();
}

public static void add(Object entity) {
Session s = null;
Transaction tx = null;
try {
s = HibernateUtil.getSession();
tx = s.beginTransaction();
s.save(entity);
tx.commit();
} finally {
if (s != null)
s.close();
}
}

public static void update(Object entity) {
Session s = null;
Transaction tx = null;
try {
s = HibernateUtil.getSession();
tx = s.beginTransaction();
s.update(entity);
tx.commit();
} finally {
if (s != null)
s.close();
}
}

public static void delete(Object entity) {
Session s = null;
Transaction tx = null;
try {
s = HibernateUtil.getSession();
tx = s.beginTransaction();
s.delete(entity);
tx.commit();
} finally {
if (s != null)
s.close();
}
}

public static Object get(Class clazz, Serializable id) {
Session s = null;
try {
s = HibernateUtil.getSession();
Object obj = s.get(clazz, id);
return obj;
} finally {
if (s != null)
s.close();
}
}
}