J2SE综合:关于private构造函数Java认证考试

文章作者 100test 发表时间 2009:04:10 00:45:33
来源 100Test.Com百考试题网

　　看下面的类:
　　HibernateSessionFactory.java
　　package zy.pro.wd.util.
　　import net.sf.hibernate.HibernateException.
　　import net.sf.hibernate.Session.
　　import net.sf.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.
　　* NOTICE: Location should be on the classpath as Hibernate uses
　　* #resourceAsStream style lookup for its configuration file. That
　　* is place the config file in a Java package - the default location
　　* is the default Java package.
　　* Examples:
　　* CONFIG_FILE_LOCATION = "/hibernate.conf.xml".
　　* CONFIG_FILE_LOCATION = "/com/foo/bar/myhiberstuff.conf.xml".
　　*/
　　private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml".
　　/** Holds a single instance of Session */
　　private static final ThreadLocal threadLocal = new ThreadLocal().
　　/** The single instance of hibernate configuration */
　　private static final Configuration cfg = new Configuration().
　　/** The single instance of hibernate SessionFactory */
　　private static net.sf.hibernate.SessionFactory sessionFactory.
　　/**
　　* Returns the ThreadLocal Session instance.　Lazy initialize
　　* the SessionFactory if needed.
　　*
　　*　@return Session
　　*　@throws HibernateException
　　*/
　　public static Session currentSession() throws HibernateException {
　　Session session = (Session) threadLocal.get().
　　if (session == null) {
　　if (sessionFactory == null) {
　　try {
　　cfg.configure(CONFIG_FILE_LOCATION).
　　sessionFactory = cfg.buildSessionFactory().
　　}
　　catch (Exception e) {
　　System.err.println("%%%% Error Creating SessionFactory %%%%").
　　e.printStackTrace().
　　}
　　}
　　session = sessionFactory.openSession().
　　threadLocal.set(session).
　　}
　　return session.
　　}
　　/**
　　*　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().
　　}
　　}
　　/**
　　* Default constructor.
　　*/