<tx:annotation-driven />
Additionally ensure that the tx namespace is defined as per the xsi:schemaLocation
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.1.xsd"
default-lazy-init="true" />
And now to the fun part! Add annotations to your code. I prefer to apply annotations to interfaces. That way all implementations of the interface are transactional.

...and Bob's your uncle!