使用ThreadLocal实现事务的管理
在HibernateSessionFactory类中，我们可以仿照Session的管理方式来实现对Transaction事务的管理！
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package com.hibernate;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
?
public class HibernateSessionFactory {
?private static String CONFIG_FILE_LOCATION = "/com/hibernate/hibernate.cfg.xml";
?
?/**
? *
? * 程序在运行过程中会启动多个线程， threadLocal可以在单个线程内实现线程内部共享数据－－－使用单例模式
? *
? */
?private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
?/**
? * 使用ThreadLocal实现事务的管理
? *
? */
?private static final ThreadLocal<Transaction> txThreadLocal = new ThreadLocal<Transaction>();
//配置文件节点<hibernate-configuration>对应读取的对象
?private static Configuration configuration = new Configuration();
//配置文件<session-factory>节点对应读取的对象
?private static org.hibernate.SessionFactory sessionFactory;
//配置文件hibernate.cfg.xml配置文件所在的路径
?private static String configFile = CONFIG_FILE_LOCATION;
?
//静态块，会早于构造函数执行
?static {
??try {
???configuration.configure(configFile);
???sessionFactory = configuration.buildSessionFactory();
??} catch (Exception e) {
???System.err.println("%%%% Error Creating SessionFactory %%%%");
???e.printStackTrace();
??}
?}
?
?
?private HibernateSessionFactory() {
?}
?/**
? * Returns the ThreadLocal Session instance. Lazy initialize the
? * <code>SessionFactory</code> if needed.
? *
? * @return Session
? * @throws HibernateException
? */
?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;
?}
?public static void beginTransaction() throws HibernateException {
??//取得已经绑定的事务
??Transaction tx = (Transaction) txThreadLocal.get();
??
??//如果事务为空，或已经提交或已经回滚，则开启一个新的事务
??if (tx == null || tx.wasCommitted() || tx.wasRolledBack()) {
???tx = getSession().beginTransaction();
???//把事务绑定的本地线程中，供提交会回滚使用
???txThreadLocal.set(tx);
??}
?}
?
?public static void commitTransaction() throws HibernateException {
??//取得已经绑定的事务
??Transaction tx = (Transaction) txThreadLocal.get();
??//如果事务不等于空，并没有提交或回滚。则提交事务
??if (tx != null && !tx.wasCommitted() && !tx.wasRolledBack()) {
???tx.commit();
??}
??//清空当前线程事务，确保下个操作取得新的事务
??txThreadLocal.set(null);
?}
?public static void rollbackTransaction() throws HibernateException {
??Transaction tx = (Transaction) txThreadLocal.get();
??if (tx != null && !tx.wasCommitted() && !tx.wasRolledBack()) {
???tx.rollback();
??}
?
??txThreadLocal.set(null);
?}
?
?
?/**
? * 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;
?}
?/**
? * return session factory
? *
? * session factory will be rebuilded in the next call
? */
?public static void setConfigFile(String configFile) {
??HibernateSessionFactory.configFile = configFile;
??sessionFactory = null;
?}
?/**
? * return hibernate configuration
? *
? */
?public static Configuration getConfiguration() {
??return configuration;
?}
}
