原理
Spring是基于proxy方式的事务实现机制。如果你的target实现了某个接口，那么Spring可以根据这个接口动态生成一个proxy，在你的service方法前后进行如下事务管理：
tx.begin();
try{
target.service();
}catch(Exception e){
tx.rollback();
}
tx.commit();
而动态代理的生成方式，Spring支持两种：
- 如果target有实现接口，那么使用JDK动态代理
- 否则使用CGLIB Proxy
Creates a JDK proxy when proxy interfaces are given, and a CGLIB proxy for the actual target class if not. Note that the latter will only work if the target class does not have final methods, as a dynamic subclass will be created at runtime.
当然，你可以通过配置强制Spring使用CGLIB Proxy方式。具体参考笔者的另一篇文章：Spring AOP internal
配置
使用TransactionProxyFactoryBean配置方式(老的方式)
There are three main properties that need to be specified:
- “transactionManager”: the PlatformTransactionManager implementation to use (for example, a JtaTransactionManager instance)
- “target”: the target object that a transactional proxy should be created for
- “transactionAttributes”: the transaction attributes (for example, propagation behavior and “readOnly” flag) per target method name (or method name pattern)
示例配置：
<?xml version= "1.0" encoding ="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<!-- PlatformTransactionManager，为了让Spring @SpringJUnit4ClassRunner @Transactional生效，id必须是transactionManager -->
<bean id="transactionManager"
class= "org.springframework.jdbc.datasource.DataSourceTransactionManager" >
<property name= "dataSource" ref ="dataSource" />
</bean>
<bean id="fooTransactionDefinition" abstract="true"
class= "org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
<property name="transactionManager" ref="transactionManager" />
<property name="transactionAttributes" >
<props>
<prop key="get*">PROPAGATION_SUPPORTS,readOnly</prop>
<prop key="find*">PROPAGATION_SUPPORTS,readOnly</prop>
<prop key="is*">PROPAGATION_SUPPORTS,readOnly</prop>
<prop key="list*">PROPAGATION_SUPPORTS,readOnly</prop>
<prop key="query*">PROPAGATION_SUPPORTS,readOnly</prop>
<prop key="*">PROPAGATION_REQUIRED </prop>
</props>
</property>
</bean>
<bean id="fooService" parent="fooTransactionDefinition">
<property name= "target">
<bean class="me.arganzheng.study.transaction.service.FooService">
...
</bean>
</property>
</bean>
<bean class= "org.springframework.beans.factory.config.PropertyPlaceholderConfigurer" >
<property name="location">
<value>classpath:db.properties</value>
</property>
</bean>
<bean id="dataSource" destroy-method="close"
class= "org.apache.commons.dbcp.BasicDataSource" >
<property name= "driverClassName" value="${jdbc.driverClassName}" />
<property name= "url" value ="${jdbc.url}" />
<property name= "username" value="${jdbc.username}" />
<property name= "password" value="${jdbc.password}" />
</bean>
</beans>
使用AOP配置方式
<?xml version= "1.0" encoding ="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:tx= "http://www.springframework.org/schema/tx"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">
<!-- 事务配置 -->
<tx:advice id="txAdvice" transaction-manager="transactionManager" >
<tx:attributes>
<tx:method name="get*" propagation="SUPPORTS" read-only="true"/>
<tx:method name="find*" propagation="SUPPORTS" read-only="true"/>
<tx:method name="is*" propagation="SUPPORTS" read-only="true"/>
<tx:method name="list*" propagation="SUPPORTS" read-only="true"/>
<tx:method name="query*" propagation="SUPPORTS" read-only="true"/>
<tx:method name="*" />
</tx:attributes>
</tx:advice>
<aop:config proxy-target-class="true">
<aop:pointcut id="serviceOperation" expression="execution(* me.arganzheng.study.transaction.service.*.*(..))" />
<aop:advisor advice-ref="txAdvice" pointcut-ref="serviceOperation" />
</aop:config>
<!-- PlatformTransactionManager，为了让Spring @SpringJUnit4ClassRunner @Transactional生效，id必须是transactionManager -->
<bean id="transactionManager"
class= "org.springframework.jdbc.datasource.DataSourceTransactionManager" >
<property name= "dataSource" ref ="dataSource" />
</bean>
<bean id="fooService" parent="fooTransactionDefinition">
<property name= "target">
<bean class="me.arganzheng.study.transaction.service.FooService">
...
</bean>
</property>
</bean>
<bean class= "org.springframework.beans.factory.config.PropertyPlaceholderConfigurer" >
<property name="location">
<value>classpath:db.properties</value>
</property>
</bean>
<bean id="dataSource" destroy-method="close"
class= "org.apache.commons.dbcp.BasicDataSource" >
<property name= "driverClassName" value="${jdbc.driverClassName}" />
<property name= "url" value ="${jdbc.url}" />
<property name= "username" value="${jdbc.username}" />
<property name= "password" value="${jdbc.password}" />
</bean>
</beans>
注意 Spring默认会将propagation设置为REQUIRED，将readOnly设置为false，并且rollback only for unchecked exceptions。另外，isolation level设置为底层数据库的default值。如果是使用JPA，isolation level 是底层的persistence provider。如果是Hibernate，所有事务的isolation level应该设置为REPEATABLE_READ。如果你没有配置propagation="SUPPORTS"而只是配置了read-only="true"，你会看到一个Spring对一个readOnly的事务也是起一个事务，并且成功后会commit改事务的哦！
[12-10 14:04:40.202][DEBUG][Thread-14] C2CTcpIoHandler:41 : (0x00497E4B: nio socket, server, /172.xxx.xxx.xxx:35216 => /10.191.xxx.xxx:xxxx) sessionOpened。
[12-10 14:04:40.206][DEBUG][Thread-14] DefaultListableBeanFactory:244 : Returning cached instance of singleton bean 'lotteryAO'
[12-10 14:04:40.206][DEBUG][Thread-14] DataSourceTransactionManager:365 : Creating new transaction with name [com.ecc.victor.buyer.activity.lottery.service.LotteryRecordService.getRecordList4o2o]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT,readOnly
[12-10 14:04:40.269][DEBUG][Thread-14] DataSourceTransactionManager:204 : Acquired Connection [jdbc:mysql://xxx.xxx.xxx.xxx:xxxxx/xxxxx?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull, UserName=xxxx@xxx.xxx.xxx.xxx, MySQL-AB JDBC Driver] for JDBC transaction
[12-10 14:04:40.299][DEBUG][Thread-14] DataSourceUtils:153 : Setting JDBC Connection [jdbc:mysql://xxx.xxx.xxx.xxx:xxxx/xxx?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull, UserName=xxx@xxx.xxx.xxx.xxx, MySQL-AB JDBC Driver] read-only
[12-10 14:04:40.330][DEBUG][Thread-14] DataSourceTransactionManager:221 : Switching JDBC Connection [jdbc:mysql://xxx.xxx.xxx.xxx:xxxx/xxxx?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull, UserName=xxxx@xxx.xxx.xxx.xxx, MySQL-AB JDBC Driver] to manual commit
[12-10 14:04:40.360][DEBUG][Thread-14] SqlMapClientTemplate:168 : Opened SqlMapSession [com.ibatis.sqlmap.engine.impl.SqlMapSessionImpl@547aaf5a] for iBATIS operation
[12-10 14:04:40.360][DEBUG][Thread-14] Connection:27 : {conn-100627} Connection
[12-10 14:04:40.360][DEBUG][Thread-14] SqlMapClientTemplate:185 : Obtained JDBC Connection [Transaction-aware proxy for target Connection from DataSource [org.apache.commons.dbcp.BasicDataSource@277889e9]] for iBATIS operation
[12-10 14:04:40.361][DEBUG][Thread-14] Connection:27 : {conn-100627} Preparing Statement: select * from xxxxxx where user_id=? and (status='xxx' or status='xxxx' or status='xxxx') and activity_id in (select id from xxxx where seller_uin=? and type='xxx')
[12-10 14:04:40.361][DEBUG][Thread-14] PreparedStatement:27 : {pstm-100628} Executing Statement: select * from xxxxx where user_id=? and (status='Hit' or status='xxxx' or status='xxx') and activity_id in (select id from t_victor_activity where seller_uin=? and type='xxxx')
[12-10 14:04:40.361][DEBUG][Thread-14] PreparedStatement:27 : {pstm-100628} Parameters: [xxx, xxxx]
[12-10 14:04:40.361][DEBUG][Thread-14] PreparedStatement:27 : {pstm-100628} Types: [java.lang.String, java.lang.Long]
[12-10 14:04:40.392][DEBUG][Thread-14] ResultSet:27 : {rset-100629} ResultSet
...
[12-10 14:04:40.395][DEBUG][Thread-14] DataSourceTransactionManager:752 : Initiating transaction commit
[12-10 14:04:40.426][DEBUG][Thread-14] DataSourceTransactionManager:264 : Committing JDBC transaction on Connection [jdbc:mysql://xxx.xxx.xxx.xxx:xxx/xxxx?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull, UserName=xxx@xxx.xxx.xxx.xxx, MySQL-AB JDBC Driver]
[12-10 14:04:40.517][DEBUG][Thread-14] DataSourceUtils:222 : Resetting read-only flag of JDBC Connection [jdbc:mysql://xxx.xxx.xxx.xxx:xxx/xxx?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull, UserName=xxx@xxx.xxx.xxx.xxx, MySQL-AB JDBC Driver]
[12-10 14:04:40.547][DEBUG][Thread-14] DataSourceTransactionManager:322 : Releasing JDBC Connection [jdbc:mysql://xxx.xxx.xxx.xxx:xxx/xxxx?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull, UserName=xxxx@xxx.xxx.xxx.xxx, MySQL-AB JDBC Driver] after transaction
[12-10 14:04:40.547][DEBUG][Thread-14] DataSourceUtils:332 : Returning JDBC Connection to DataSource
[12-10 14:04:40.547][DEBUG][Thread-14] LotteryActivityService:128 : LotteryAO getLotteryRecord getRecordList4o2o cost[341]ms
[12-10 14:04:40.548][DEBUG][Thread-14] LotteryActivityService:142 : LotteryAO getLotteryRecord cost[342]ms
使用@Transactional注解配置方式
其实从Spring2.x就开始支持Anotation方式进行事务配置了。不过相对于XML配置，粒度比较细。
package org.springframework.transaction.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.springframework.transaction.TransactionDefinition;
@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface Transactional {
/**
* A qualifier value for the specified transaction.
* <p>May be used to determine the target transaction manager,
* matching the qualifier value (or the bean name) of a specific
* {@link org.springframework.transaction.PlatformTransactionManager}
* bean definition.
*/
String value() default "";
/**
* The transaction propagation type.
* Defaults to {@link Propagation#REQUIRED}.
* @see org.springframework.transaction.interceptor.TransactionAttribute#getPropagationBehavior()
*/
Propagation propagation() default Propagation.REQUIRED;
/**
* The transaction isolation level.
* Defaults to {@link Isolation#DEFAULT}.
* @see org.springframework.transaction.interceptor.TransactionAttribute#getIsolationLevel()
*/
Isolation isolation() default Isolation.DEFAULT;
/**
* The timeout for this transaction.
* Defaults to the default timeout of the underlying transaction system.
* @see org.springframework.transaction.interceptor.TransactionAttribute#getTimeout()
*/
int timeout() default TransactionDefinition.TIMEOUT_DEFAULT;
/**
* {@code true} if the transaction is read-only.
* Defaults to {@code false}.
* <p>This just serves as a hint for the actual transaction subsystem;
* it will <i>not necessarily</i> cause failure of write access attempts.
* A transaction manager which cannot interpret the read-only hint will
* <i>not</i> throw an exception when asked for a read-only transaction.
* @see org.springframework.transaction.interceptor.TransactionAttribute#isReadOnly()
*/
boolean readOnly() default false;
/**
* Defines zero (0) or more exception {@link Class classes}, which must be a
* subclass of {@link Throwable}, indicating which exception types must cause
* a transaction rollback.
* <p>This is the preferred way to construct a rollback rule, matching the
* exception class and subclasses.
* <p>Similar to {@link org.springframework.transaction.interceptor.RollbackRuleAttribute#RollbackRuleAttribute(Class clazz)}
*/
Class<? extends Throwable>[] rollbackFor() default {};
/**
* Defines zero (0) or more exception names (for exceptions which must be a
* subclass of {@link Throwable}), indicating which exception types must cause
* a transaction rollback.
* <p>This can be a substring, with no wildcard support at present.
* A value of "ServletException" would match
* {@link javax.servlet.ServletException} and subclasses, for example.
* <p><b>NB: </b>Consider carefully how specific the pattern is, and whether
* to include package information (which isn't mandatory). For example,
* "Exception" will match nearly anything, and will probably hide other rules.
* "java.lang.Exception" would be correct if "Exception" was meant to define
* a rule for all checked exceptions. With more unusual {@link Exception}
* names such as "BaseBusinessException" there is no need to use a FQN.
* <p>Similar to {@link org.springframework.transaction.interceptor.RollbackRuleAttribute#RollbackRuleAttribute(String exceptionName)}
*/
String[] rollbackForClassName() default {};
/**
* Defines zero (0) or more exception {@link Class Classes}, which must be a
* subclass of {@link Throwable}, indicating which exception types must <b>not</b>
* cause a transaction rollback.
* <p>This is the preferred way to construct a rollback rule, matching the
* exception class and subclasses.
* <p>Similar to {@link org.springframework.transaction.interceptor.NoRollbackRuleAttribute#NoRollbackRuleAttribute(Class clazz)}
*/
Class<? extends Throwable>[] noRollbackFor() default {};
/**
* Defines zero (0) or more exception names (for exceptions which must be a
* subclass of {@link Throwable}) indicating which exception types must <b>not</b>
* cause a transaction rollback.
* <p>See the description of {@link #rollbackForClassName()} for more info on how
* the specified names are treated.
* <p>Similar to {@link org.springframework.transaction.interceptor.NoRollbackRuleAttribute#NoRollbackRuleAttribute(String exceptionName)}
*/
String[] noRollbackForClassName() default {};
}
可以注在方法或者类上，基本是跟XML配置的<tx:method/>标签对应。
参考文档
- 官方文档永远都是值得一看的：10. Transaction Management
- 关于AOP编程方式实现事务：7. Aspect Oriented Programming with Spring
- 这里有个非常详细的例子：Declaring Transaction Attributes on Spring’s TransactionProxyFactoryBean
- 结合这篇文章就可以搞定了：Basic transactions in Spring using TransactionProxyFactoryBean。基本是step-by-step，还有说明。
