Spring中事務管理淺談

Spring中對事務的聲明式管理

拿一個XML舉例

1. <?xml version="1.0" encoding="UTF-8"?>
2. <beans xmlns="http://www.springframework.org/schema/beans"
3. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4. xmlns:aop="http://www.springframework.org/schema/aop"
5. xmlns:tx="http://www.springframework.org/schema/tx"
6. xsi:schemaLocation="
7. http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
8. http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd
9. http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd">
12. 事務管理目標Service
13. <bean id="fooService" class="x.y.service.DefaultFooService"/>
15. 切面配置，配置了切入點是執行FooService下的所有方法 和 切入點調用的通知器為txAdvice
16. <aop:config>
17. <aop:pointcut id="fooServiceOperation" expression="execution(* x.y.service.FooService.*(..))"/>
18. <aop:advisor advice-ref="txAdvice" pointcut-ref="fooServiceOperation"/>
19. </aop:config>
21. 該通知器的具體配置，所使用的事務管理器，所配置的事務規則
22. <tx:advice id="txAdvice" transaction-manager="txManager">
23. <!-- the transactional semantics... -->
25. <tx:attributes>
26. <!-- all methods starting with 'get' are read-only -->
28. <tx:method name="get*" read-only="true"/>
29. <!-- other methods use the default transaction settings (see below) -->
31. <tx:method name="*"/>
32. </tx:attributes>
33. </tx:advice>
35. 所選用的事務管理器，和作為啟動參數塞入的dataSource
36. <bean id="txManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
37. <property name="dataSource" ref="dataSource"/>
38. </bean>
41. 連接數據庫的dataSource
42. <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
43. <property name="driverClassName" value="Oracle.jdbc.driver.OracleDriver"/>
44. <property name="url" value="jdbc:oracle:thin:@rj-t42:1521:elvis"/>
45. <property name="username" value="scott"/>
46. <property name="password" value="tiger"/>
47. </bean>
49. </beans>

Spring中對事務管理的底層實現

以上的方法，選用了Spring本身自帶的JDBC的事務控制器做處理。

相關代碼集中在DataSourceTransactionManager中

比如，事務的取得並且將取得的事務捆綁進當前線程中

1. @Override
2. protected Object doGetTransaction() {
3. DataSourceTransactionObject txObject = new DataSourceTransactionObject();
4. txObject.setSavepointAllowed(isNestedTransactionAllowed());
5. ConnectionHolder conHolder =
6. (ConnectionHolder) TransactionSynchronizationManager.getResource(this.dataSource);
7. txObject.setConnectionHolder(conHolder, false);
8. return txObject;
9. }

在比如事務的開始，

1. /**
2. * This implementation sets the isolation level but ignores the timeout.
3. */
4. @Override
5. protected void doBegin(Object transaction, TransactionDefinition definition) {
6. DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
7. Connection con = null;
9. try {
10. if (txObject.getConnectionHolder() == null ||
11. txObject.getConnectionHolder().isSynchronizedWithTransaction()) {
12. Connection newCon = this.dataSource.getConnection();
13. if (logger.isDebugEnabled()) {
14. logger.debug("Acquired Connection [" + newCon + "] for JDBC transaction");
15. }
16. txObject.setConnectionHolder(new ConnectionHolder(newCon), true);
17. }
19. txObject.getConnectionHolder().setSynchronizedWithTransaction(true);
20. con = txObject.getConnectionHolder().getConnection();
22. Integer previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
23. txObject.setPreviousIsolationLevel(previousIsolationLevel);
25. // Switch to manual commit if necessary. This is very expensive in some JDBC drivers,
26. // so we don't want to do it unnecessarily (for example if we've explicitly
27. // configured the connection pool to set it already).
28. if (con.getAutoCommit()) {
29. txObject.setMustRestoreAutoCommit(true);
30. if (logger.isDebugEnabled()) {
31. logger.debug("Switching JDBC Connection [" + con + "] to manual commit");
32. }
33. con.setAutoCommit(false);
34. }
35. txObject.getConnectionHolder().setTransactionActive(true);
37. int timeout = determineTimeout(definition);
38. if (timeout != TransactionDefinition.TIMEOUT_DEFAULT) {
39. txObject.getConnectionHolder().setTimeoutInSeconds(timeout);
40. }
42. // Bind the session holder to the thread.
43. if (txObject.isNewConnectionHolder()) {
44. TransactionSynchronizationManager.bindResource(getDataSource(), txObject.getConnectionHolder());
45. }
46. }
48. catch (Exception ex) {
49. DataSourceUtils.releaseConnection(con, this.dataSource);
50. throw new CannotCreateTransactionException("Could not open JDBC Connection for transaction", ex);
51. }
52. }

等等這裡就不多說了，起個頭。