上一篇中：
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：
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：
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。
职责委托给了SessionImpl，打开org.hibernate.impl.SessionImpl.java，看看实现代码：
1
SessionImpl(
2
final
Connectionconnection,
3
final
SessionFactoryImplfactory,
4
final
boolean
autoclose,
5
final
long
timestamp,
6
final
Interceptorinterceptor,
7
final
EntityModeentityMode,
8
final
boolean
flushBeforeCompletionEnabled,
9
final
boolean
autoCloseSessionEnabled,
10
final
ConnectionReleaseModeconnectionReleaseMode)
{
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(
"
openedsessionattimestamp:
"
+
timestamp);
30
}
31
}
SessionImpl(
2
final
Connectionconnection,
3
final
SessionFactoryImplfactory,
4
final
boolean
autoclose,
5
final
long
timestamp,
6
final
Interceptorinterceptor,
7
final
EntityModeentityMode,
8
final
boolean
flushBeforeCompletionEnabled,
9
final
boolean
autoCloseSessionEnabled,
10
final
ConnectionReleaseModeconnectionReleaseMode)
{
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(
"
openedsessionattimestamp:
"
+
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(Contextowner,Connectionconnection,Interceptorinterceptor)
{
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
}
public
JDBCContext(Contextowner,Connectionconnection,Interceptorinterceptor)
{
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(
"
openingJDBCconnection
"
);
7
try
{
8
connection
=
factory.getConnectionProvider().getConnection();
9
}
10
catch
(SQLExceptionsqle)
{
11
throw
JDBCExceptionHelper.convert(
12
factory.getSQLExceptionConverter(),
13
sqle,
14
"
Cannotopenconnection
"
15
);
16
}
17
18
callback.connectionOpened();
//
registersynch;stats.connect()
19
}
private
void
openConnection()
throws
HibernateException
{
2
if
(connection
!=
null
)
{
3
return
;
4
}
5
6
log.debug(
"
openingJDBCconnection
"
);
7
try
{
8
connection
=
factory.getConnectionProvider().getConnection();
9
}
10
catch
(SQLExceptionsqle)
{
11
throw
JDBCExceptionHelper.convert(
12
factory.getSQLExceptionConverter(),
13
sqle,
14
"
Cannotopenconnection
"
15
);
16
}
17
18
callback.connectionOpened();
//
registersynch;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。
