Question

我有一个简单的类，它启动3个线程并在每个线程中保存一个新对象。但我得到了一些我无法理解的异常。任何人都可以帮助我理解为什么例外吗？

package test;

import java.util.Date;

import org.hibernate.Session;

import domain.Event;

import util.HibernateUtil;

public class EventBeanTest {

    public static void main(String [] args) {

        Event e1 = new Event();
        e1.setTitle("111");
        e1.setDate(new Date());

        Event e2 = new Event();
        e2.setTitle("222");
        e2.setDate(new Date());

        Event e3 = new Event();
        e3.setTitle("333");
        e3.setDate(new Date());


        Thread t1 = new Thread(new EventRunnable(e1));
        Thread t2 = new Thread(new EventRunnable(e2));
        Thread t3 = new Thread(new EventRunnable(e3));

        t1.setName("event - 111");
        t2.setName("event - 222");
        t3.setName("event - 333");

        t1.start();
        t2.start();
        t3.start();

    }

}

class EventRunnable implements Runnable {
    private Event event;

    public EventRunnable(Event event) {
        this.event = event;
    }

    public void run() {

        System.out.println("Starting thread : " + Thread.currentThread().getName());

        Session session = HibernateUtil.getSessionFactory().getCurrentSession();

        session.beginTransaction();

        session.saveOrUpdate(event);
        session.getTransaction().commit();

        HibernateUtil.getSessionFactory().close();

        System.out.println("Finishing thread : " + Thread.currentThread().getName());

    }
}

这是显示异常的日志文件的相关部分：

Hibernate: select max(EVENT_ID) from test.EVENTS
Hibernate: insert into test.EVENTS (EVENT_DATE, TITLE, EVENT_ID) values (?, ?, ?)
Hibernate: insert into test.EVENTS (EVENT_DATE, TITLE, EVENT_ID) values (?, ?, ?)
Hibernate: insert into test.EVENTS (EVENT_DATE, TITLE, EVENT_ID) values (?, ?, ?)
Apr 22, 2012 2:46:55 PM org.hibernate.service.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop
INFO: HHH000030: Cleaning up connection pool [jdbc:mysql://localhost:3306/test]
Finishing thread : event - 333
Apr 22, 2012 2:46:55 PM org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction afterAfterCompletion
INFO: HHH000425: Could not close session; swallowing exception[org.hibernate.service.UnknownServiceException: Unknown service requested [org.hibernate.stat.spi.StatisticsImplementor]] as transaction completed
Exception in thread "event - 222" org.hibernate.service.UnknownServiceException: Unknown service requested [org.hibernate.stat.spi.StatisticsImplementor]
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:126)
    at org.hibernate.internal.SessionFactoryImpl.getStatisticsImplementor(SessionFactoryImpl.java:1708)
    at org.hibernate.internal.SessionFactoryImpl.getStatistics(SessionFactoryImpl.java:1704)
    at org.hibernate.engine.transaction.internal.TransactionCoordinatorImpl.afterTransaction(TransactionCoordinatorImpl.java:140)
    at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.afterTransactionCompletion(JdbcTransaction.java:138)
    at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.commit(AbstractTransactionImpl.java:184)
    at test.EventRunnable.run(EventBeanTest.java:60)
    at java.lang.Thread.run(Thread.java:722)
Apr 22, 2012 2:46:55 PM org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction afterAfterCompletion
INFO: HHH000425: Could not close session; swallowing exception[org.hibernate.service.UnknownServiceException: Unknown service requested [org.hibernate.stat.spi.StatisticsImplementor]] as transaction completed
Exception in thread "event - 111" org.hibernate.service.UnknownServiceException: Unknown service requested [org.hibernate.stat.spi.StatisticsImplementor]
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:126)
    at org.hibernate.internal.SessionFactoryImpl.getStatisticsImplementor(SessionFactoryImpl.java:1708)
    at org.hibernate.internal.SessionFactoryImpl.getStatistics(SessionFactoryImpl.java:1704)
    at org.hibernate.engine.transaction.internal.TransactionCoordinatorImpl.afterTransaction(TransactionCoordinatorImpl.java:140)
    at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.afterTransactionCompletion(JdbcTransaction.java:138)
    at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.commit(AbstractTransactionImpl.java:184)
    at test.EventRunnable.run(EventBeanTest.java:60)
    at java.lang.Thread.run(Thread.java:722)

编辑1

<?xml version='1.0' encoding='utf-8'?>

<session-factory>

    <!-- Database connection settings -->
    <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="connection.url">jdbc:mysql://localhost:3306/test</property>
    <property name="connection.username">vishnu</property>
    <property name="connection.password">con02305</property>

    <!-- JDBC connection pool (use the built-in) -->
    <property name="connection.pool_size">1</property>

    <!-- SQL dialect -->
    <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>

    <!-- Enable Hibernate's automatic session context management -->
    <property name="current_session_context_class">thread</property>

    <!-- Disable the second-level cache  -->
    <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>

    <!-- Echo all executed SQL to stdout -->
    <property name="show_sql">true</property>

    <!-- Drop and re-create the database schema on startup 
    <property name="hbm2ddl.auto">update</property> -->

    <property name="default_schema">test</property>
    <property name="show_sql">true</property>

    <mapping resource="domain/Event.hbm.xml"/>

</session-factory>

Answer 1

Hibernate中的Session对象不是线程安全的，除非您同步访问Session对象，否则不应在不同的线程中使用相同的会话。

Answer 2

在.openSession()之后致电.getCurrentSession()而不是getSessionFactory()。
sessionFactory对象是线程安全的，但每个Session对象应该是单线程的。

Answer 3

会话实际上是一个Unit of Work，它应绑定到当前正在执行的Thread。单个事务中的多个DML操作的工作组，只有在所有操作都成功时才能成功。因此会话是原子的，而原子性意味着一个操作线程。

Session也是第一级缓存，因此在当前Session中，无论您调用session.get（）或session.load（）多少次，您都将获得相同的Entity对象引用。如果会话是线程安全的而不是刷新时间，则可以执行其他事务中介更改。因此，Session必须与其他正在执行的Session隔离，而隔离意味着单个操作线程。

因此，会话并不意味着保持原子性和隔离要求的线程安全。

Answer 4

如果它对其他人有帮助，对我来说，这意味着“你在之前的单元测试中做了一个模拟间谍（数据库）”，它以某种方式进行了休眠。去图。

Hibernate UnknownServiceException：在事务完成时请求未知服务

4 个答案: