相关疑难解决方法(0)

我需要确保许多并发用户能够访问数据库.虽然在每次提交后我都会关闭会话,但有时我的代码会遇到以下错误,但是当我执行相同的操作几次时,它会超过错误并起作用.

我的休眠是4.2.1.Final

Messages:   
nested transactions not supported
File:   org/hibernate/engine/transaction/spi/AbstractTransactionImpl.java
Line number:    152

我的守则

session = HibernateUtil.getSession();
session.getTransaction().begin();       OR session.beginTransaction();
       ...   to do ....
session.getTransaction().commit();
session.close();                        OR HibernateUtil.closeSession();

的HibernateUtil

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

public class HibernateUtil {

   private static ServiceRegistry serviceRegistry;
   private static final ThreadLocal<Session> threadLocal = new ThreadLocal();
   private static SessionFactory sessionFactory;
    private static SessionFactory configureSessionFactory() {
        try {

            Configuration configuration = new Configuration();
            configuration.configure();
            serviceRegistry = new ServiceRegistryBuilder()
                                 .applySettings(configuration.getProperties())
                                 .buildServiceRegistry();
            sessionFactory …

为什么JTA不支持嵌套事务？是因为实施它们的复杂性(我怀疑)还是一些设计原则？

我刚刚设置了一个目前为止仍然非常小的项目maven/jpa/hibernate项目,我试图坚持一个对象.

我的课很简单:

@Entity
public class Person {
    @Id @GeneratedValue
    private int id;
    private String name;
}

我的persistence.xml也是非常基本的:

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
    version="2.0">
    <persistence-unit name="Fahrplan_v2">
        <class>model.Person</class>
        <properties>
            <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver" />
            <property name="hibernate.connection.url" value="jdbc:hsqldb:file:data/db/db" />
            <property name="hibernate.connection.username" value="sa" />
            <property name="hibernate.connection.password" value="" />
            <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect" />
            <property name="hibernate.hbm2ddl.auto" value="update" />
        </properties>
    </persistence-unit>
</persistence>

最后这是我用来持久保存对象的代码:

EntityManager em = entityManagerFactory.createEntityManager();
em.getTransaction().begin();
em.persist(person);
// em.flush(); <- does not effect outcome.
em.getTransaction().commit();
em.close();

现在我希望在这里发生两件事:首先,我希望创建Person表(由于hibernate.hbm2ddl.auto = update).这已经发生了一次,它正确地写出来了

CREATE MEMORY TABLE PUBLIC.PERSON(
    ID INTEGER GENERATED …