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。
