找不到休眠数据库驱动程序类

Question

我对Hibernate还不是很有经验，并且在尝试使用Hibernate 4.3和PostgreSQL为我的本地数据库创建测试数据时遇到了问题。

我有另一个项目，我以完全相同

的方式执行此操作并且在那里工作，所以我做了完全相同的设置，但使用了另一个数据库，但现在在我当前的项目中，我得到以下异常：

exception.DBException: Could not configure Hibernate!
    at dao.BenutzerDAO.<init>(BenutzerDAO.java:48)
    at export.ExportDBSchema.main(ExportDBSchema.java:16)
Caused by: org.hibernate.boot.registry.classloading.spi.ClassLoadingException: Unable to load class [org.postgresql.Driver]
    at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java:245)
    at org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl.loadDriverIfPossible(DriverManagerConnectionProviderImpl.java:200)
    at org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl.buildCreator(DriverManagerConnectionProviderImpl.java:156)
    at org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl.configure(DriverManagerConnectionProviderImpl.java:95)
    at org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:89)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:206)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:178)
    at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.buildJdbcConnectionAccess(JdbcServicesImpl.java:260)
    at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.configure(JdbcServicesImpl.java:94)
    at org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:89)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:206)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:178)
    at org.hibernate.cfg.Configuration.buildTypeRegistrations(Configuration.java:1885)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1843)
    at dao.BenutzerDAO.<init>(BenutzerDAO.java:45)
    ... 1 more
Caused by: java.lang.ClassNotFoundException: Could not load requested class : org.postgresql.Driver
    at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl$AggregatedClassLoader.findClass(ClassLoaderServiceImpl.java:230)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:340)
    at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java:242)
    ... 15 more

我

寻找了可能的解决方案，但没有一个对我有用：

-）在 Manifest.mf 中指定 jar 的类路径 -> 不起作用
-）将 postgresql-9.4.1208.jre6.jar 放在 WEB-INF 下的 lib 文件夹中 -> 不起作用
-）在 Configuration（）.configure（） 中指定 hibernate.cfg.xml 文件;-> 不起作用

我使用 Glassfish 4.1 并且 org.postgres.Driver.class 存在，为什么找不到它？

我的冬眠.cfg.xml：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
  <session-factory>
    <property name="hibernate.dialect">org.hibernate.dialect.PostgreSQLDialect</property>
    <property name="hibernate.connection.driver_class">org.postgresql.Driver</property>
    <property name="hibernate.connection.url">jdbc:postgresql://localhost:5432/Testdb</property>
    <property name="hibernate.connection.username">username</property>
    <property name="hibernate.hbm2ddl.auto">create-drop</property>
    <property name="hibernate.connection.password">password</property>
    <mapping class="entity.Benutzer"/>
  </session-factory>
</hibernate-configuration>

BenutzerDAO中的方法.java发生异常的地方：

try {
            if (sessionFactory == null) {
                Configuration conf = new Configuration().configure();
                StandardServiceRegistryBuilder builder
                        = new StandardServiceRegistryBuilder();
                builder.applySettings(conf.getProperties());
                sessionFactory = conf.buildSessionFactory(builder.build());
            }
        } catch (Throwable ex) {
            throw new DBException("Could not configure Hibernate!", ex);
        }

我将非常感谢每一个答案。

Answer 1

try
{
    Configuration cfg =new Configuration();
    cfg.configure("hibernate.cfg.xml");
    SessionFactory sf=cfg.buildSessionFactory();
    Session sess=sf.openSession();
    ----------------------------------
your code
------------------------------
Transaction tx=sess.beginTransaction();
sess.save(e);
tx.commit();
sess.flush();
sess.close();
sf.close();

}
catch(Exception e)
{
System.out.println("e="+e.getMessage());
}