问题描述

SSH-hibernate4.3.8-HibernateSessionFactory.java

---

初学者问题：
1）web开发，哪里有靠谱的HibernateSessionFactory.java 及其对应的hibernate.cfg.xml？感觉自己手上的这两个文件的问题多多，各种debug，很耗时间
2） hibernate的jar包要放WEB-INF/lib目录下？又或者跟hibernate.cfg.xml里面的某个property的设置有关？

sever一开始起不来，网上搜了下，把hibernate的jar包要放WEB-INF/lib目录下，server就可以起来了。奇怪，struts的jar放WEB-INF/lib目录下可以理解，怎么hibernate的也要放在这个目录下？

开发环境
eclipse: Luna Service Release 1a (4.4.1)
mysql: 5.6
struts: 2.3.20

hibernate: 4.3.8

现象：
第一次从web访问，正常。说明struts, mysql工作都是正常的。
第二次起从web访问，报下面的错误。
将下面的代码注释掉后，再从web访问，每次正常了。问题是：一直不close SessionFactory 不会有问题吗？ 是否要优化HibernateSessionFactory.java？

HibernateTestAction.java

 //sf.close();  即SessionFactory一直不close

 Debug - execute - after getSessionFactory
Debug - execute - throw exception
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:201)
    at org.hibernate.internal.AbstractSessionImpl.getJdbcConnectionAccess(AbstractSessionImpl.java:341)
    at org.hibernate.engine.jdbc.internal.JdbcCoordinatorImpl.<init>(JdbcCoordinatorImpl.java:114)
    at org.hibernate.engine.transaction.internal.TransactionCoordinatorImpl.<init>(TransactionCoordinatorImpl.java:89)
    at org.hibernate.internal.SessionImpl.<init>(SessionImpl.java:258)

---

代码：
HibernateSessionFactory.java

 package hibernate;

import org.hibernate.HibernateException;
import org.hibernate.Interceptor;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;

/**
 * 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 {
    private static final SessionFactory sessionFactory = buildSessionFactory();

    private static SessionFactory buildSessionFactory() {
        System.out.println("sessionFactory - on buildSessionFactory");
        try {
            Configuration cfg = new Configuration().configure();
            StandardServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
                                .applySettings(cfg.getProperties()).build();
            SessionFactory sessionFactory = cfg.buildSessionFactory(serviceRegistry);

            return sessionFactory;
        }
        catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.out.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        System.out.println("sessionFactory - on getSessionFactory");
        if (sessionFactory == null)
            System.out.println("build sessionFactory - fail");
        else
            System.out.println("build sessionFactory - succe");
        return sessionFactory;
    }

}

hibernate.cfg.xml

 <?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
          "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
          "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<!-- Generated by MyEclipse Hibernate Tools.                   -->
<hibernate-configuration>
    <session-factory>
        <!--
        <property name="hibernate.transaction.factory_class">
        org.hibernate.transaction.JTATransactionFactory
        </property>
        <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>
        -->        

        <property name="cache.use_query_cache">true</property>
        <property name="cache.provider_class">org.hibernate.cache.HashtableCacheProvider</property>
        <property name="cache.region.factory_class">org.hibernate.cache.ehcache.EhCacheRegionFactory</property>

        <property name="connection.username">root</property>
        <property name="connection.password">admin</property>

        <property name="connection.url">
            jdbc:mysql://localhost:3306/db_database10
        </property>
        <property name="dialect">
            org.hibernate.dialect.MySQLDialect
        </property>
        <property name="cache.use_query_cache">true</property>
        <property name="cache.provider_class">
            org.hibernate.cache.HashtableCacheProvider
        </property>
        <property name="show_sql">true</property>
        <property name="connection.driver_class">
            com.mysql.jdbc.Driver
        </property>
        <mapping resource="mapping.xml" />
    </session-factory>
</hibernate-configuration>

HibernateTestAction.java

 public class HibernateTestAction extends ActionSupport implements ModelDriven<Book> {
...
    public String execute() {
        SessionFactory sf =  HibernateSessionFactory.getSessionFactory();

        try {
            System.out.println("Debug - execute - after getSessionFactory ");

            Session s = sf.openSession();
            s.beginTransaction();
            System.out.println("Debug - execute - after beginTransaction ");

            String hql = "from Book";
            Query query;
            query = s.createQuery(hql);
            List<Book> books = query.list();
            dataMap.put("data", books);

            System.out.println("Debug - execute - query.list ");

            for(Book bookTemp: books)
            {
               System.out.println(bookTemp.toString());
            }
            s.getTransaction().commit();
            System.out.println("Debug - execute - after commit");
            s.close();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            System.out.println("Debug - execute - throw exception ");
            e.printStackTrace();
        }
        sf.close();

        dataMap.put("status", "SUCCESS");

        return SUCCESS;
    }
...
}

---

解决方案

我们一般采用spring来管理sessionFactory，如果用hibernate自己管理的话开发最好用单例模式创建sessionFactory，
sessionFactory只创建一次就可以，是不需要关闭的。因为session是线程不安全的，所以每次用hibenate的时候记得要
及时关闭session，即每次查询操作数据库的时候需要sessionFactory来openSession，每次操作完数据库或者查询完数据库
要记得及时close掉session就可以了。

如果你看过你的server的文件结构你就明白为什么所有jar包都放在WEB-INF/lib下，WEB-INF下放着你的所有的代码， 你的所有Java代码被编译成
classes文件放在了WEB-INF/classes中相当于src，所有jar包放在WEB-INF/jar下，WEB-INF中还有web.xml配置文件，WEB-INF外面放页面，相当于webroot

如果你觉得DEBUG多多，一个是删掉你的代码中的sysout，一个不显示你的sql语句，从hibernate.cfg.xml中
true中true改成false，一个是你是不是放hibernate包放进去日志包log4j系列，如果是就修改你的
log4j.properties文件，把里面的log4j.rootLogger=DEBUG改成log4j.rootLogger=info就可以大大减少你的DEBUG输出了。

解决方案二：

谢谢 kunkunqianqian。

用下面的HibernateSessionFactoryV1.java，问题解决了

package hibernate;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.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 HibernateSessionFactoryV1 {
    /**
     * Location of hibernate.cfg.xml file.
     * Location should be on the classpath as Hibernate uses
     * #resourceAsStream style lookup for its configuration file.
     * The default classpath location of the hibernate config file is
     * in the default package. Use #setConfigFile() to update
     * the location of the configuration file for the current session.
     */
    private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
    private static org.hibernate.SessionFactory sessionFactory;
    private static Configuration configuration = new Configuration();
    private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";
    private static String configFile = CONFIG_FILE_LOCATION;

    static {
        try {
            configuration.configure(configFile);
            StandardServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
                                                            .applySettings(configuration.getProperties()).build();
            sessionFactory = configuration.buildSessionFactory(serviceRegistry);
        } catch (Exception e) {
            System.err.println("%%%% Error Creating SessionFactory %%%%");
            e.printStackTrace();
        }
    }

    private HibernateSessionFactoryV1() {
    }

    /**
    * Returns the ThreadLocal Session instance.  Lazy initialize
    * the <code>SessionFactory</code> if needed.
    *
    *  @return Session
    *  @throws HibernateException
    */
    public static Session getSession() throws HibernateException {
        System.out.println("Debug - on HibernateSessionFactoryV1.getSession ");
        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;
    }

    /**
    *  Rebuild hibernate session factory
    *
    */
    public static void rebuildSessionFactory() {
        try {
            configuration.configure(configFile);
            StandardServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
                                                            .applySettings(configuration.getProperties()).build();
            sessionFactory = configuration.buildSessionFactory(serviceRegistry);

        } 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) {
        HibernateSessionFactoryV1.configFile = configFile;
        sessionFactory = null;
    }

    /**
    *  return hibernate configuration
    *
    */
    public static Configuration getConfiguration() {
        return configuration;
    }
}