Pre-loading and lazy loading in spring with tomcat

Question

I have used Pre-loading in spring framework,so my beans are created when loaded in container. My beans instances are singleton. But I want to use lazy loading. To my understanding, when using lazy loading beans' instances are created when the bean is requested, but is not present in the container.

But my requirement is when the operation on that bean finishes, I want to garbage collect that bean instance. And again, when that bean is requested I want to create the bean again in lazy loading way.

So, as far as I know when beans are deployed in container again to create beans instance after bean instance is garbage collected, we have to redeploy it in the container. I want to garbage collect bean instance at runtime after it is used, and create its instance again when it is requested. Is it possible using spring and tomcat without redeploying?

I am not sure that lazy loading is usable at all - for example I know a near realtime trading system of a famous bank where all the beans are configured on the start(and container starts several minutes). Also I'm almost sure tha the beans you lazily load are singletons, it's unlikely they eat up more than several mibs of the memory, turning on lazy load is fhe last thing to do. If you have classloader memory leaks in tomcat then search how to fix them. If you run out of heap space then use special tools described in Java Performance book. — Boris Treukhov
– Boris Treukhov, Commented Jan 30, 2013 at 12:52

jmruc · Accepted Answer · 2013-01-30 12:42:31Z

2

You need to use prototype scoped beans - these are beans that are created when requested, and are garbage collected like regular objects.

Take a look at the documentation page. You can declare a bean as prototype be setting the scope to prototype:

<bean id="accountService" class="com.foo.DefaultAccountService" scope="prototype"/>

answered Jan 30, 2013 at 12:42

jmruc

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2 Comments

abishkar bhattarai Over a year ago

My one confusion. suppose if for accountService i have declared destroy-method="cleanResource"> in scope prototype .So,when the requested operation on this bean finishes ,then it goes for garbage collection.If i declare destroy-method="cleanResource"> then does it call cleanResource method on that bean and it is garbaged collected Or it is directly garbaged collected without calling cleanResource method .Suppose that resource is some Input/output and i want to release that resource before it is garbaged.OR we should close the application context to call this method cleanResource on this bean.

jmruc Over a year ago

@abishkar Spring only creates prototype beans, but does not call the destroy method. If using such a bean, you are responsible for manually cleaning after your bean. Closing the application context won't help, you have to call whatever destroy methods you have on that object.

ach · Accepted Answer · 2013-01-30 16:07:32Z

2

Bean scoping is probably the most straightforward way to do it. You'll probably want "prototype", but "session" and "request" are also available inside of a web container.

If you're using "session" or "request" and are injecting the bean into a singleton bean, you'll need to use <aop:scoped-proxy/>:

<bean id="userPreferences" class="com.foo.UserPreferences" scope="session">
    <aop:scoped-proxy/>
</bean>

edited Jan 30, 2013 at 16:07

answered Jan 30, 2013 at 13:58

ach

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