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Hibernate源代码分析(一)：设计属于我的SessionFactory和ConnectionProvider 分析到了SessionFactoryImpl.openSession()方法，该方法将其
职责委托给了SessionImpl，打开org.hibernate.impl.SessionImpl.java，看看实现代码：
1
SessionImpl(
2 final Connection connection,
3 final SessionFactoryImpl factory,
4 final boolean autoclose,
5 final long timestamp,
6 final Interceptor interceptor,
7 final EntityMode entityMode,
8 final boolean flushBeforeCompletionEnabled,
9 final boolean autoCloseSessionEnabled,
10
final ConnectionReleaseMode connectionReleaseMode) 
{
11
super( factory );
12 this.rootSession = null;
13 this.timestamp = timestamp;
14 this.entityMode = entityMode;
15 this.interceptor = interceptor;
16 this.listeners = factory.getEventListeners();
17 this.actionQueue = new ActionQueue( this );
18 this.persistenceContext = new StatefulPersistenceContext( this );
19 this.flushBeforeCompletionEnabled = flushBeforeCompletionEnabled;
20 this.autoCloseSessionEnabled = autoCloseSessionEnabled;
21 this.connectionReleaseMode = connectionReleaseMode;
22 this.jdbcContext = new JDBCContext( this, connection, interceptor );
23
24
if ( factory.getStatistics().isStatisticsEnabled() ) {
25 factory.getStatisticsImplementor().openSession();
26
}
27
28 if ( log.isDebugEnabled() ) {
29 log.debug( "opened session at timestamp: " + timestamp );
30 }
31
}
我们关注的就是数据库连接，重点关注第22行，在该行将Connection对象传递给了JDBCContext,通过观察前面的代码我们可以发现，JTASessionContext.buildOrObtainSession() 方法传递的Connection对象为null，这个可以说，Connection对象的获得将由
ConnectionProvider接口的实现类来完成。
接下来看看JDBCContent类的构造函数，跳转到org.hibernate.jdbc.JDBCContent.java，程序代码如下：
1 public JDBCContext(Context owner, Connection connection, Interceptor interceptor) {
2 this.owner = owner;
3 this.connectionManager = new ConnectionManager(
4 owner.getFactory(),
5 this,
6 owner.getConnectionReleaseMode(),
7 connection,
8 interceptor
9 );
10
11 final boolean registerSynchronization = owner.isAutoCloseSessionEnabled()
12 || owner.isFlushBeforeCompletionEnabled()
13 || owner.getConnectionReleaseMode() == ConnectionReleaseMode.AFTER_TRANSACTION;
14 if ( registerSynchronization ) {
15 registerSynchronizationIfPossible();
16 }
17 }
这段程序代码里创建了一个新的对象connectionManager，我们跟踪一下org.hibernate.jdbc.ConnectionManager.java，在这个文件里可以
发现一个方法openConnection()，代码如下：
1 private void openConnection() throws HibernateException {
2 if ( connection != null ) {
3 return;
4 }
5
6 log.debug("opening JDBC connection");
7 try {
8 connection = factory.getConnectionProvider().getConnection();
9 }
10 catch (SQLException sqle) {
11 throw JDBCExceptionHelper.convert(
12 factory.getSQLExceptionConverter(),
13 sqle,
14 "Cannot open connection"
15 );
16 }
17
18 callback.connectionOpened(); // register synch; stats.connect()
19 }
现在，最有价值的发现出来了，在第8行，这里就是从缓冲池获得数据库连接的代码。
接下来我们可以设计实现ConnectionProvider的具体类了。