org.hibernate.connection包分析-DriverManagerConnectionProvider,DatasourceConnect

org.hibernate.connection包分析--DriverManagerConnectionProvider,DatasourceConnect
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1. //$Id:?DriverManagerConnectionProvider.java?7888?2005-08-12?21:22:38Z?oneovthafew?$????
2. package?org.hibernate.connection;????
3. ????
4. import?java.sql.Connection;????
5. import?java.sql.DriverManager;????
6. import?java.sql.SQLException;????
7. import?java.util.ArrayList;????
8. import?java.util.Iterator;????
9. import?java.util.Properties;????
10. ????
11. import?org.slf4j.Logger;????
12. import?org.slf4j.LoggerFactory;????
13. import?org.hibernate.HibernateException;????
14. import?org.hibernate.cfg.Environment;????
15. import?org.hibernate.util.PropertiesHelper;????
16. import?org.hibernate.util.ReflectHelper;????
17. ????
18. /**??
19. ?*?A?connection?provider?that?uses?<tt>java.sql.DriverManager</tt>.?This?provider??
20. ?*?also?implements?a?very?rudimentary?connection?pool.??
21. ?*?@see?ConnectionProvider??
22. ?*?@author?Gavin?King??
23. ?*/????
24. public?class?DriverManagerConnectionProvider?implements?ConnectionProvider?{????
25. ????
26. ????private?String?url;????
27. ????private?Properties?connectionProps;????
28. ????private?Integer?isolation;????
29. ????private?final?ArrayList?pool?=?new?ArrayList();????
30. ????private?int?poolSize;????
31. ????private?int?checkedOut?=?0;????
32. ????private?boolean?autocommit;????
33. ????
34. ????private?static?final?Logger?log?=?LoggerFactory.getLogger(DriverManagerConnectionProvider.class);????
35. ????
36. ????public?void?configure(Properties?props)?throws?HibernateException?{????
37. ????
38. ????????String?driverClass?=?props.getProperty(Environment.DRIVER);????
39. ????
40. ????????poolSize?=?PropertiesHelper.getInt(Environment.POOL_SIZE,?props,?20);?//default?pool?size?20????
41. ????????log.info("Using?Hibernate?built-in?connection?pool?(not?for?production?use!)");????
42. ????????log.info("Hibernate?connection?pool?size:?"?+?poolSize);????
43. ????????????
44. ????????autocommit?=?PropertiesHelper.getBoolean(Environment.AUTOCOMMIT,?props);????
45. ????????log.info("autocommit?mode:?"?+?autocommit);????
46. ????
47. ????????isolation?=?PropertiesHelper.getInteger(Environment.ISOLATION,?props);????
48. ????????if?(isolation!=null)????
49. ????????log.info(?"JDBC?isolation?level:?"?+?Environment.isolationLevelToString(?isolation.intValue()?)?);????
50. ????
51. ????????if?(driverClass==null)?{????
52. ????????????log.warn("no?JDBC?Driver?class?was?specified?by?property?"?+?Environment.DRIVER);????
53. ????????}????
54. ????????else?{????
55. ????????????try?{????
56. ????????????????//?trying?via?forName()?first?to?be?as?close?to?DriverManager's?semantics????
57. ????????????????Class.forName(driverClass);????
58. ????????????}????
59. ????????????catch?(ClassNotFoundException?cnfe)?{????
60. ????????????????try?{????
61. ????????????????????ReflectHelper.classForName(driverClass);????
62. ????????????????}????
63. ????????????????catch?(ClassNotFoundException?e)?{????
64. ????????????????????String?msg?=?"JDBC?Driver?class?not?found:?"?+?driverClass;????
65. ????????????????????log.error(?msg,?e?);????
66. ????????????????????throw?new?HibernateException(msg,?e);????
67. ????????????????}????
68. ????????????}????
69. ????????}????
70. ????
71. ????????url?=?props.getProperty(?Environment.URL?);????
72. ????????if?(?url?==?null?)?{????
73. ????????????String?msg?=?"JDBC?URL?was?not?specified?by?property?"?+?Environment.URL;????
74. ????????????log.error(?msg?);????
75. ????????????throw?new?HibernateException(?msg?);????
76. ????????}????
77. ????
78. ????????connectionProps?=?ConnectionProviderFactory.getConnectionProperties(?props?);????
79. ????
80. ????????log.info(?"using?driver:?"?+?driverClass?+?"?at?URL:?"?+?url?);????
81. ????????//?if?debug?level?is?enabled,?then?log?the?password,?otherwise?mask?it????
82. ????????if?(?log.isDebugEnabled()?)?{????
83. ????????????log.info(?"connection?properties:?"?+?connectionProps?);????
84. ????????}?????
85. ????????else?if?(?log.isInfoEnabled()?)?{????
86. ????????????log.info(?"connection?properties:?"?+?PropertiesHelper.maskOut(connectionProps,?"password")?);????
87. ????????}????
88. ????
89. ????}????
90. ????
91. ????public?Connection?getConnection()?throws?SQLException?{????
92. ????
93. ????????if?(?log.isTraceEnabled()?)?log.trace(?"total?checked-out?connections:?"?+?checkedOut?);????
94. ????
95. ????????synchronized?(pool)?{????
96. ????????????if?(?!pool.isEmpty()?)?{????
97. ????????????????int?last?=?pool.size()?-?1;????
98. ????????????????if?(?log.isTraceEnabled()?)?{????
99. ????????????????????log.trace("using?pooled?JDBC?connection,?pool?size:?"?+?last);????
100. ????????????????????checkedOut++;????
101. ????????????????}????
102. ????????????????Connection?pooled?=?(Connection)?pool.remove(last);????
103. ????????????????if?(isolation!=null)?pooled.setTransactionIsolation(?isolation.intValue()?);????
104. ????????????????if?(?pooled.getAutoCommit()!=autocommit?)?pooled.setAutoCommit(autocommit);????
105. ????????????????return?pooled;????
106. ????????????}????
107. ????????}????
108. ????
109. ????????log.debug("opening?new?JDBC?connection");????
110. ????????Connection?conn?=?DriverManager.getConnection(url,?connectionProps);????
111. ????????if?(isolation!=null)?conn.setTransactionIsolation(?isolation.intValue()?);????
112. ????????if?(?conn.getAutoCommit()!=autocommit?)?conn.setAutoCommit(autocommit);????
113. ????
114. ????????if?(?log.isDebugEnabled()?)?{????
115. ????????????log.debug(?"created?connection?to:?"?+?url?+?",?Isolation?Level:?"?+?conn.getTransactionIsolation()?);????
116. ????????}????
117. ????????if?(?log.isTraceEnabled()?)?checkedOut++;????
118. ????
119. ????????return?conn;????
120. ????}????
121. ????
122. ????public?void?closeConnection(Connection?conn)?throws?SQLException?{????
123. ????
124. ????????if?(?log.isDebugEnabled()?)?checkedOut--;????
125. ????
126. ????????synchronized?(pool)?{????
127. ????????????int?currentSize?=?pool.size();????
128. ????????????if?(?currentSize?<?poolSize?)?{????
129. ????????????????if?(?log.isTraceEnabled()?)?log.trace("returning?connection?to?pool,?pool?size:?"?+?(currentSize?+?1)?);????
130. ????????????????pool.add(conn);????
131. ????????????????return;????
132. ????????????}????
133. ????????}????
134. ????
135. ????????log.debug("closing?JDBC?connection");????
136. ????
137. ????????conn.close();????
138. ????
139. ????}????
140. ????
141. ????protected?void?finalize()?{????
142. ????????close();????
143. ????}????
144. ????
145. ????public?void?close()?{????
146. ????
147. ????????log.info("cleaning?up?connection?pool:?"?+?url);????
148. ????
149. ????????Iterator?iter?=?pool.iterator();????
150. ????????while?(?iter.hasNext()?)?{????
151. ????????????try?{????
152. ????????????????(?(Connection)?iter.next()?).close();????
153. ????????????}????
154. ????????????catch?(SQLException?sqle)?{????
155. ????????????????log.warn("problem?closing?pooled?connection",?sqle);????
156. ????????????}????
157. ????????}????
158. ????????pool.clear();????
159. ????
160. ????}????
161. ????
162. ????/**??
163. ?????*?@see?ConnectionProvider#supportsAggressiveRelease()??
164. ?????*/????
165. ????public?boolean?supportsAggressiveRelease()?{????
166. ????????return?false;????
167. ????}????
168. ????
169. }??

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1. ???

DriverManagerConnectionProvider类继承了ConnectionProvider接口，主要是使用用户提供的JDBC驱动程序来连接数据库，或者使用连接池的方式来连接数据库。 ?? 一个典型的JDBC驱动连接数据库的方式：

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1. ?<property?name="connection.driver_class">com.mysql.jdbc.Driver</property>????
2. ????
3. ????
4. <!--?连接数据库的URL-->????
5. ????
6. <property?name="connection.url">?????
7. ????
8. jdbc:mysql://localhost:3306/schoolproject????
9. ????
10. </property>????
11. ????
12. <property?name="connection.useUnicode">true</property>????
13. ????
14. <property?name="connection.characterEncoding">UTF-8</property>????
15. ????
16. ????
17. <!--连接的登录名-->????
18. ????
19. <property?name="connection.username">root</property>????
20. ????
21. ????
22. <!—登录密码-->????
23. ????
24. <property?name="connection.password"></property>????
25. ????
26. ????
27. <!--是否将运行期生成的SQL输出到日志以供调试-->????
28. ????
29. <property?name="show_sql">true</property>????
30. ????
31. ????
32. <!--指定连接的语言-->????
33. ????
34. <property?name="dialect">org.hibernate.dialect.MySQLDialect</property>??

?至于连接池，由于在hibernate3.0中，已经不再支持dbcp了，hibernate的作者在hibernate.org中，明确指出在实践中发现dbcp有BUG,在某些种情会产生很多空连接不能释放，所以抛弃了对dbcp的支持。因此官方推荐使用c3p0或Proxool连接池。

? C3P0连接配置

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1. <!—JDBC驱动程序-->????
2. ????
3. <property?name="connection.driver_class">com.mysql.jdbc.Driver</property>????
4. ????
5. <!--?连接数据库的URL-->????
6. ????
7. <property?name="connection.url">?????
8. ????
9. jdbc:mysql://localhost:3306/schoolproject????
10. ????
11. </property>????
12. ????
13. <property?name="connection.useUnicode">true</property>????
14. ????
15. <property?name="connection.characterEncoding">UTF-8</property>????
16. ????
17. <!--连接的登录名-->????
18. ????
19. <property?name="connection.username">root</property>????
20. ????
21. <!--登录密码-->????
22. ????
23. <property?name="connection.password"></property>????
24. ????
25. <!--?C3P0连接池设定-->????
26. ????
27. <property?name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider????
28. </property>????
29. ????
30. <property?name="hibernate.c3p0.max_size">20</property>????
31. ????
32. <property?name="hibernate.c3p0.min_size">5</property>????
33. ????
34. <property?name="hibernate.c3p0.timeout">120</property>????
35. ????
36. <property?name="hibernate.c3p0.max_statements">100</property>????
37. ????
38. <property?name="hibernate.c3p0.idle_test_period">120</property>????
39. ????
40. <property?name="hibernate.c3p0.acquire_increment">2</property>????
41. ????
42. <!--是否将运行期生成的SQL输出到日志以供调试-->????
43. ????
44. <property?name="show_sql">true</property>????
45. ????
46. <!--指定连接的语言-->????
47. ????
48. <property?name="dialect">org.hibernate.dialect.MySQLDialect</property>??

?　　首先看DriverManagerConnectionProvider的configure(Properties props)方法，在这个方法中并没有去判断是否使用了连接池，真正判断使用连接池是在ConnectionProviderFactory这个类中，我们以后会分析。???

　　DriverManagerConnectionProvider这个类只是初始化了最基本的连接配置，有如下几个：hibernate.connection.driver_class(JDBC驱动类)、hibernate.connection.pool_size(连接池容量的上限数目)、hibernate.connection.autocommit(允许被缓存的JDBC连接开启自动自动提交)、hibernate.connection.isolation(设置JDBC事务隔离级别，可查看java.sql.Connection来了解各个值的具体意义，但请注意多数数据库都不支持所有的隔离级别，取值1，2，4，8)。无论你是使用JDBC还是使用连接池方式，这几个最基本的设置都是要先初始化的。其中pool_size的默认值为20。

　　configure(Properties props)方法中的这个语句connectionProps = ConnectionProviderFactory.getConnectionProperties( props );值得注意， ConnectionProviderFactory.getConnectionProperties( props )主要是把HIBERNATE.CFG或者HIBERNATE.PROPERTIES的配置文件中的属性重新封装到另一个Properties 类——connectionProps中，且connectionProps的键值与 HIBERNATE.CFG或者HIBERNATE.PROPERTIES中的键值相比是没有“hibernate.connection”这样的字样的，比如，在HIBERNATE.PROPERTIES中定义的“hibernate.connection.pool_size”属性键，到该Properties 类 中的键就成了“pool_size ”。connectionProps主要是为后面的getConnection()方法而提供的。 ??

　　接下来是getConnection()方法，在这里我们发现了synchronized关键字，这个关键字是加在pool这个对象上的，也就是说某个时刻只有其中的一个线程可以访问这个对象的synchronized数据。每个对象都有一个"锁标志"，当这个对象的一个线程访问这个对象的某个synchronized数据时，这个对象的所有被synchronized修饰的数据将被上锁（因为"锁标志"被当前线程拿走了），只有当前线程访问完它要访问的synchronized数据时，当前线程才会释放"锁标志"，这样同一个对象的其它线程才有机会访问synchronized数据。pool是什么？它是一个ArrayList，也就是连接池，里面都是一个个的Connection对象，这个可以在后面的closeConnection(Connection conn)体现出来，正在pool上加synchronized修饰符就保证了多个线程不能并发访问此ArrayList而生成不正确的结果。当调用getConnection()方法时，我们可以看到连接池就移除了一个连接。

　　Connection conn = DriverManager.getConnection(url, connectionProps)语句中我们可以看到全局变量connectionProps是传入到了这个方法中的，返回了一个Connection 对象。 ??

　　?closeConnection(Connection conn)方法是将连接重新放回到连接池。 ??

　　close()方法清空了连接池，关闭所有连接。 ??

　　supportsAggressiveRelease()方法返回的是false,表示连接释放模式会被设置为hibernate.connection.release_mode.AFTER_TRANSACTION也就是说在org.hibernate.Transaction结束后释放连接。

DatasourceConnectionProvider类分析 ?? DatasourceConnectionProvider类比较简单，不同的是,它通过JNDI的方式来查找数据源来获得连接，这个类中要注意的方法是supportsAggressiveRelease()它返回的是true，表示在使用数据源连接的情况下，支持使用hibernate.connection.release_mode.AFTER_STATEMENT这一个设置。

UserSuppliedConnectionProvider类分析 ?? UserSuppliedConnectionProvider 这个类是留给用户自己扩展的，基本上什么都不干。

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