我知道已经有类似的问题,但那里的答案对我没有帮助。那么请您介意一下我的特定问题吗?
我对Hibernate不是很熟悉,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完成它并且它工作,所以我做了完全相同的设置但使用另一个数据库,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
我搜索了可能的解决方案,但没有一个能为我工作:
- )在Manifest.mf中指定jar的Classpath - &gt;不工作 - )将postgresql-9.4.1208.jre6.jar放在WEB-INF下的lib文件夹中 - &gt;不工作 - )在Configuration()中指定hibernate.cfg.xml文件.configure(); - &GT;没工作
我使用Glassfish 4.1并且org.postgres.Driver.class已经存在,那么为什么找不到它?
我的hibernate.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>
发生异常的DAO类中的方法:
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);
}
我会非常感谢每一个答案。
答案 0 :(得分:3)
你很亲密!
您需要将postgresql-<version>.jar
直接放在 servlet容器的lib
文件夹中。
例如,如果你正在使用 Apache Tomcat ,只需将你的 jar 放在<TOMCAT_ROOT>/lib
下,你应该全部设置好。
答案 1 :(得分:3)
如果您正在使用Maven或Gradle。
您可以将其添加到ur pom.xml中进行Maven操作
<!-- https://mvnrepository.com/artifact/org.postgresql/postgresql -->
<dependency>
<groupId>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<version>42.2.4</version>
</dependency>
这对于gradle
// https://mvnrepository.com/artifact/org.postgresql/postgresql
compile group: 'org.postgresql', name: 'postgresql', version: '42.2.4'