正确决解Hibernate4.*中：Connection cannot be null when 'hibernate.dialect' not set

http://www.cnblogs.com/cnscoo/archive/2012/09/17/2689021.html

今天在做Hibernate4.*的项目中，使用了以下的配置：

hibernate.cfg.xml

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

 2  <!DOCTYPE hibernate-configuration PUBLIC

 3      "-//Hibernate/Hibernate Configuration DTD 3.0//EN"

 4      "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

 5  <hibernate-configuration>

 6      <session-factory>

 7          <property name="show_sql">true</property>

 8          <property name="format_sql">true</property>

 9          <property name="dialect">org.hibernate.dialect.SQLiteDialect</property>

10          <property name="connection.driver_class">org.sqlite.JDBC</property>

11          <property name="connection.url">jdbc:sqlite:D:\Documents\Dbs\test.db</property>

12          <property name="connection.username"></property>

13          <property name="connection.password"></property>

14  

15          <mapping resource="test/model/Blackey.hbm.xml" />

16      </session-factory>

17  </hibernate-configuration>    

然后在Text.java中测试：

 import org.hibernate.Session;

 import org.hibernate.SessionFactory;

 import org.hibernate.cfg.Configuration;

 import org.hibernate.service.ServiceRegistryBuilder;

 import test.model.Blackey;

 public class Test {

 	public static void main(String [] args){

 		Blackey bk = new Blackey();

 		bk.setName("测试");

 		bk.setVersion("1.0.4");

 		bk.setUid("Test");

 		bk.setKey("1fD46a709C920a01477632");

 		bk.setDescribe("该注册码只能用于该版本！");

 		

 		Configuration cfg = new Configuration().configure();

 		SessionFactory sf = cfg.buildSessionFactory(new ServiceRegistryBuilder().buildServiceRegistry());　　//以前的cfg.buildSessionFactory()方法被废弃，查网上大多使用该方法

 		Session session = sf.openSession();

 		session.beginTransaction();

 		session.save(bk);

 		session.getTransaction().commit();

 		session.close();

 		sf.close();

 		

 	}

 }

　　结果显示报错：

Exception in thread "main" org.hibernate.HibernateException: Connection cannot be null when 'hibernate.dialect' not set

 	at org.hibernate.service.jdbc.dialect.internal.DialectFactoryImpl.determineDialect(DialectFactoryImpl.java:97)

 	at org.hibernate.service.jdbc.dialect.internal.DialectFactoryImpl.buildDialect(DialectFactoryImpl.java:67)

 	at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.configure(JdbcServicesImpl.java:174)

 	at org.hibernate.service.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:75)

 	at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:159)

 	at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:131)

 	at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:73)

 	at org.hibernate.cfg.Configuration.buildSettingsInternal(Configuration.java:2283)

 	at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:2279)

 	at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1748)

 	at Test.main(Test.java:19)

　　一直让人很费解，因为显而易见，我的dialect是明确定义了的（说明一下：我个人已经把org.hibernate.dialect.SQLiteDialect文件打包到了hibernate-core-4.1.*.jar中，所以不会有此类不存在的可能），但为什么说我的dialect未定义呢？

　　在网上找相关资料，发现很多人都存在这个问题，可惜没有发现很好的解决办法，有人只是测试使用 hibernate.properties来进行配置，则可以成功。个人还是觉得使用xml配置好，转向国外网站查看，终于看到了一个老外的解决办法：

将

SessionFactory sf = cfg.buildSessionFactory(new ServiceRegistryBuilder().buildServiceRegistry());

替换成

SessionFactory sf = cfg.buildSessionFactory(new ServiceRegistryBuilder().applySettings(cfg.getProperties()).buildServiceRegistry());

表示应用hibernate.cfg.xml中的属性配置，接着运行，发现又错了：

 Exception in thread "main" org.hibernate.HibernateException: Error applying BeanValidation relational constraints

 	at org.hibernate.cfg.beanvalidation.BeanValidationIntegrator.applyRelationalConstraints(BeanValidationIntegrator.java:219)

 	at org.hibernate.cfg.beanvalidation.BeanValidationIntegrator.integrate(BeanValidationIntegrator.java:126)

 	at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:301)

 	at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1750)

 	at Test.main(Test.java:19)

 Caused by: java.lang.reflect.InvocationTargetException

 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

 	at java.lang.reflect.Method.invoke(Method.java:597)

 	at org.hibernate.cfg.beanvalidation.BeanValidationIntegrator.applyRelationalConstraints(BeanValidationIntegrator.java:208)

 	... 4 more

 Caused by: org.hibernate.HibernateException: Unable to build the default ValidatorFactory

 	at org.hibernate.cfg.beanvalidation.TypeSafeActivator.getValidatorFactory(TypeSafeActivator.java:524)

 	at org.hibernate.cfg.beanvalidation.TypeSafeActivator.applyDDL(TypeSafeActivator.java:119)

 	... 9 more

 Caused by: javax.validation.ValidationException: Unable to instantiate Configuration.

 	at javax.validation.Validation$GenericBootstrapImpl.configure(Validation.java:272)

 	at javax.validation.Validation.buildDefaultValidatorFactory(Validation.java:111)

 	at org.hibernate.cfg.beanvalidation.TypeSafeActivator.getValidatorFactory(TypeSafeActivator.java:521)

 	... 10 more

 Caused by: java.lang.NullPointerException

 	at java.util.ResourceBundle.getBundle(ResourceBundle.java:960)

 	at org.hibernate.validator.engine.ResourceBundleMessageInterpolator.loadBundle(ResourceBundleMessageInterpolator.java:202)

 	at org.hibernate.validator.engine.ResourceBundleMessageInterpolator.getFileBasedResourceBundle(ResourceBundleMessageInterpolator.java:182)

 	at org.hibernate.validator.engine.ResourceBundleMessageInterpolator.<init>(ResourceBundleMessageInterpolator.java:81)

 	at org.hibernate.validator.engine.ResourceBundleMessageInterpolator.<init>(ResourceBundleMessageInterpolator.java:73)

 	at org.hibernate.validator.engine.ConfigurationImpl.<init>(ConfigurationImpl.java:57)

 	at org.hibernate.validator.HibernateValidator.createGenericConfiguration(HibernateValidator.java:43)

 	at javax.validation.Validation$GenericBootstrapImpl.configure(Validation.java:269)

 	... 12 more

从网上搜了一下，发现还需要在hibernate.cfg.xml中加入一条配置：

<property name="javax.persistence.validation.mode">none</property>

关键在于Unable to instantiate Configuration， 如不添加默认会要求Validation provider。

做完这些，然后运行Test.java，一切正常。 OK，问题解决。