Question

前几天已经开始阅读有关Hibernate的书（Manning Java Persistance with Hibernate）。

在第一个示例中，作者展示了在尝试使用hibernate映射和SessionFactory时Hibernate的工作原理。在下一个示例中，作者用javax.persistence注释替换了hibernate映射。下一步 - 作者用EntityManagerFactory替换SessionFactory。在这里，我有一个问题。

我设法在我的计算机上重现所有示例，除了最后一个。在执行期间，我收到下一个错误：

Exception in thread "main" javax.persistence.PersistenceException: Unable to build entity manager factory
    at org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:83)
    at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:54)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:39)
    at hello.HelloWorld.main(Unknown Source)
Caused by: org.hibernate.boot.registry.classloading.spi.ClassLoadingException: HHH010003: JDBC Driver class not found: 
            org.hsqldb.jdbcDriver

    at org.hibernate.c3p0.internal.C3P0ConnectionProvider.configure(C3P0ConnectionProvider.java:148)
    at org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:111)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:234)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:206)
    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:111)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:234)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:206)
    at org.hibernate.cfg.Configuration.buildTypeRegistrations(Configuration.java:1887)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1845)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:857)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:850)
    at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.withTccl(ClassLoaderServiceImpl.java:425)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:849)
    at org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:75)
    ... 4 more
Caused by: org.hibernate.boot.registry.classloading.spi.ClassLoadingException: Unable to load class [
            org.hsqldb.jdbcDriver
        ]
    at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java:245)
    at org.hibernate.c3p0.internal.C3P0ConnectionProvider.configure(C3P0ConnectionProvider.java:145)
    ... 19 more
Caused by: java.lang.ClassNotFoundException: Could not load requested class : 
            org.hsqldb.jdbcDriver

    at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl$AggregatedClassLoader.findClass(ClassLoaderServiceImpl.java:230)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:274)
    at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java:242)
    ... 20 more
Java Result: 1

我已经检查了几次。我的lib目录中有一个hsqldb.jar（甚至是这个jar文件中的jdbcDriver.class），但程序不起作用。 Libs与之前的例子相同（一切都在以前工作）。

PS：Standallone应用程序。这里的文件内容：等/ persistence.xml中：

<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_1_0.xsd"
             version="1.0">
    <persistence-unit name="helloworld">

        <properties>
            <property name="hibernate.ejb.cfgfile"
                      value="/hibernate.cfg.xml"/>
        </properties>
    </persistence-unit>
</persistence>

等/ HelloWorld.java：

package hello;

import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

public class HelloWorld {
  public static void main(String[] args) throws ClassNotFoundException {
    // Start EntityManagerFactory
    EntityManagerFactory emf =
        Persistence.createEntityManagerFactory("helloworld");

    emf.close();
  }
}

hibernate.cfg.xml中：

<!DOCTYPE hibernate-configuration SYSTEM
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">
            org.hsqldb.jdbcDriver
        </property>
        <property name="hibernate.connection.url">
            jdbc:hsqldb:hsql://localhost
        </property>
        <property name="hibernate.connection.username">
            sa
        </property>
        <property name="hibernate.dialect">
            org.hibernate.dialect.HSQLDialect
        </property>
        <!-- Use the C3P0 connection pool provider -->
        <property name="hibernate.c3p0.min_size">5</property>
        <property name="hibernate.c3p0.max_size">20</property>
        <property name="hibernate.c3p0.timeout">300</property>
        <property name="hibernate.c3p0.max_statements">50</property>
        <property name="hibernate.c3p0.idle_test_period">3000</property>
        <!-- Show and print nice SQL on stdout -->
        <property name="show_sql">true</property>
        <property name="format_sql">true</property>
        <!-- List of XML mapping files -->
    </session-factory>
</hibernate-configuration>

PS2：删除其他空格后，看起来它无法连接到db。我仍然可以看到有关缺少驱动程序的错误：

Exception in thread "main" javax.persistence.PersistenceException: org.hibernate.exception.GenericJDBCException: Could not open connection
    at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1763)
    at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1677)
    at org.hibernate.jpa.spi.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:1771)
    at org.hibernate.jpa.internal.TransactionImpl.begin(TransactionImpl.java:64)
    at hello.HelloWorld.main(Unknown Source)
Caused by: org.hibernate.exception.GenericJDBCException: Could not open connection
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:54)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:112)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:235)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:171)
    at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.doBegin(JdbcTransaction.java:67)
    at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.begin(AbstractTransactionImpl.java:162)
    at org.hibernate.internal.SessionImpl.beginTransaction(SessionImpl.java:1471)
    at org.hibernate.jpa.internal.TransactionImpl.begin(TransactionImpl.java:61)
    ... 1 more
Caused by: java.sql.SQLException: Connections could not be acquired from the underlying database!
    at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:118)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:689)
    at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:140)
    at org.hibernate.c3p0.internal.C3P0ConnectionProvider.getConnection(C3P0ConnectionProvider.java:90)
    at org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection(AbstractSessionImpl.java:380)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:228)
    ... 6 more
Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.
    at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1418)
    at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:606)
    at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:526)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutAndMarkConnectionInUse(C3P0PooledConnectionPool.java:755)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:682)
    ... 10 more
Java Result: 1

WARNING: com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@4b76d64a -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception: 
java.sql.SQLException: No suitable driver
    at java.sql.DriverManager.getDriver(DriverManager.java:278)
    at com.mchange.v2.c3p0.DriverManagerDataSource.driver(DriverManagerDataSource.java:240)
    at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:146)
    at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:195)
    at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:184)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:200)
    at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1086)
    at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1073)
    at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:44)
    at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1810)
    at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:648)

Answer 1

看起来你的hibernate.cfg.xml文件中的驱动程序类属性周围有一些额外的空格。尝试更改以下行

<property name="hibernate.connection.driver_class">
  org.hsqldb.jdbcDriver
</property>

删除额外的空格，如下所示：

<property name="hibernate.connection.driver_class">org.hsqldb.jdbcDriver</property>

修改您还需要从其他XML标记中删除空格，因此您应该最终得到：

<!DOCTYPE hibernate-configuration SYSTEM "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="hibernate.connection.driver_class">org.hsqldb.jdbcDriver</property> <property name="hibernate.connection.url">jdbc:hsqldb:hsql://localhost</property> <property name="hibernate.connection.username">sa</property> <property name="hibernate.dialect">org.hibernate.dialect.HSQLDialect</property>  <property name="hibernate.c3p0.min_size">5</property> <property name="hibernate.c3p0.max_size">20</property> <property name="hibernate.c3p0.timeout">300</property> <property name="hibernate.c3p0.max_statements">50</property> <property name="hibernate.c3p0.idle_test_period">3000</property>  <property name="show_sql">true</property> <property name="format_sql">true</property>  </session-factory> </hibernate-configuration>

虽然您当前的网址jdbc:hsqldb:hsql://localhost假设您的计算机上已经运行了hsql数据库。如果您希望java启动内存数据库，可以将URL更改为jdbc:hsqldb:mem://localhost。

无法加载请求的类org.hsqldb.jdbcDriver

1 个答案: