<tx:annotation-driven/>

<bean id="transactionManager1" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
  <property name="dataSource" ref="datasource1"></property>
  <qualifier value="datasource1Tx"/>
</bean>

<bean id="transactionManager2" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
  <property name="dataSource" ref="datasource2"></property>
  <qualifier value="datasource2Tx"/>
</bean>

public class TransactionalService {

  @Transactional("datasource1Tx")
  public void setSomethingInDatasource1() { ... }

  @Transactional("datasource2Tx")
  public void doSomethingInDatasource2() { ... }
}