作为简单的一个单件模式，

getSessionFactory()函数返回null是一个不合理的决定，可以返回一个没有初始化的SessionFactory对象，但是返回null就和这种模式的语意有冲突了。

 

以下是用myeclipse5自动生成的代码：

 

package model.sessionfatory;

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

public class HibernateSessionFactory {

   
    private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";
 private static final ThreadLocal threadLocal = new ThreadLocal();
    private  static Configuration configuration = new Configuration();
    private static org.hibernate.SessionFactory sessionFactory;
    private static String configFile = CONFIG_FILE_LOCATION;

    private HibernateSessionFactory() {
    }
 
 
    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 rebuildSessionFactory() {
  try {
   configuration.configure(configFile);
   sessionFactory = configuration.buildSessionFactory();
  } catch (Exception e) {
   System.err
     .println("%%%% Error Creating SessionFactory %%%%");
   e.printStackTrace();
  }
 }

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

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

 
 public static org.hibernate.SessionFactory getSessionFactory() {
  return sessionFactory;
 }

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

 
 public static Configuration getConfiguration() {
  return configuration;
 }

}

 

里边的这个函数：

 public static org.hibernate.SessionFactory getSessionFactory() {
  return sessionFactory;
 }

 

是否应该修改为：

 public static org.hibernate.SessionFactory getSessionFactory() {

  rebuildSessionFactory();
  return sessionFactory;
 }

 

这样调用代码：

  dao.setSessionFactory(HibernateSessionFactory.getSessionFactory());

会报错误：

java.lang.IllegalArgumentException: sessionFactory is required
 at org.springframework.orm.hibernate3.HibernateAccessor.afterPropertiesSet(HibernateAccessor.java:318)
 at org.springframework.orm.hibernate3.HibernateTemplate.<init>(HibernateTemplate.java:147)
 at org.springframework.orm.hibernate3.support.HibernateDaoSupport.createHibernateTemplate(HibernateDaoSupport.java:83)
 at org.springframework.orm.hibernate3.support.HibernateDaoSupport.setSessionFactory(HibernateDaoSupport.java:70)
 at test.TestOrgTypeDAO.testFindById(TestOrgTypeDAO.java:66)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
 at java.lang.reflect.Method.invoke(Unknown Source)
 at junit.framework.TestCase.runTest(TestCase.java:154)
 at junit.framework.TestCase.runBare(TestCase.java:127)
 at junit.framework.TestResult$1.protect(TestResult.java:106)
 at junit.framework.TestResult.runProtected(TestResult.java:124)
 at junit.framework.TestResult.run(TestResult.java:109)
 at junit.framework.TestCase.run(TestCase.java:118)
 at junit.framework.TestSuite.runTest(TestSuite.java:208)
 at junit.framework.TestSuite.run(TestSuite.java:203)
 at org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestReference.run(JUnit3TestReference.java:128)
 at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)

 

而这样调用却不会错误：

  HibernateSessionFactory.rebuildSessionFactory();
  dao.setSessionFactory(HibernateSessionFactory.getSessionFactory());