The ConcurrencyThrottleInterceptor is a great bit of stuff to limit your use of heavy weight resources.
Use it simply by creating the bean:
<bean id="global_concurrency" class="org.springframework.aop.interceptor.ConcurrencyThrottleInterceptor" singleton="false">
<property name="concurrencyLimit" value="5"/>
</bean>
Then weaving an aspect
<bean class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator">
<property name="beanNames">
<value>SomeThing</value>
</property>
<property name="interceptorNames">
<list>
<value>global_concurrency</value>
</list>
</property>
</bean>
However there is an important thing to note, which may-or-may not be completely obvious... the singleton must be set to false, otherwise you are saying that only a certain number of simultaneous invocations are allowed for all the beans you list, not just for each one individually.
