一、SessionFactory.openSession()
1、获取Connection
这里会通过调用hibernate的ConnectionProvider接口的getConnection()获取Connection,而实际执行的有三个类继承ConnectionProvider:
1、DatasourceConnectionProviderImpl通过数据源获取:dataSource.getConnection();
2、DriverManagerConnectionProviderImpl通过ConnectionCreator获取:connectionCreator.createConnection();
3、UserSuppliedConnectionProviderImpl仅仅是抛出异常;
这里详细说明一下第一种:hibernate和各种连接池的联系是通过java的DateSource,hibernate使用DateSource的接口,各种连接池提供DateSource的实现类。而我们则是把该实现类定义为Bean。比如在tomcat.jdbc.pool中,dataSource.getConnection()这个方法实际上是通过连接池的ConnectionPool的ProxyClassConstructor.newInstance()获取Connection。
2、openSession()的实现代码(hibernate),简略:
package org.hibernate.internal;
import java.sql.Connection;
import org.hibernate.Interceptor;
import org.hibernate.Session;
import org.hibernate.SessionEventListener;
import org.hibernate.engine.spi.SessionBuilderImplementor;
import org.hibernate.engine.spi.SessionFactoryImplementor;
import org.hibernate.engine.spi.SessionOwner;
import org.hibernate.internal.SessionImpl;
public final class SessionFactoryImpl implements SessionFactoryImplementor {
static class SessionBuilderImpl implements SessionBuilderImplementor {
private final SessionFactoryImpl sessionFactory;
private Connection connection;
@Override
public Session openSession() {
final SessionImpl session = new SessionImpl(
connection,
sessionFactory,
sessionOwner,
getTransactionCoordinator(),
getTransactionCompletionProcesses(),
autoJoinTransactions,
sessionFactory.settings.getRegionFactory().nextTimestamp(),
interceptor,
flushBeforeCompletion,
autoClose,
connectionReleaseMode,
tenantIdentifier
);
for ( SessionEventListener listener : listeners ) {
session.getEventListenerManager().addListener( listener );
}
return session;
}
}
}
因此有时候我们说:Hibernate session就是java.sql.Connection的一层高级封装,一个session对应了一个Connection。