Speedup development by making spring beans lazy

In the Spring Framework you can specify on a bean level, or on a bean xml, that a bean must be instantiated lazily.

Of course you do not want to this in production, because the beans should be instantiated at deploy time, not slow down the requests of an innocent end user.

But it can be a handy feature when you use it for deployment time: it speeds up your build cycle, because beans you don't touch by your request, aren't instantiated at all.
Now we do have a problem: how can we set all beans to lazy-init="true" without doing this in production.
You can alter all context files and add the lazy-init="true" to all bean definitions, or even add the default-lazy-init="true" on the outer beans XML element. But when you go into production mode you have to change everything back which can be a pain in the **s.

I found a little solution which programmatically marks all beans as lazy. This is done by a subclass of the normal XmlWebApplicationContext, which overrides the loadBeanDefinitions method. It also has an attribute to specify beans which we do want to preinstantiate: e.g. the SessionFactory because we always need that one.

public class LazyXmlWebApplicationContext extends XmlWebApplicationContext {

 private List<String> preInstantiableBeans = Arrays.asList(new String[] {"sessFactory"});
   

 /**
  * @see org.springframework.web.context.support.XmlWebApplicationContext
  */
 protected void loadBeanDefinitions(XmlBeanDefinitionReader aReader)
   throws IOException {
  super.loadBeanDefinitions(aReader);
   
  String[] beanDefinitionNames =
    aReader.getBeanFactory().getBeanDefinitionNames();
  for (int i = 0; i < beanDefinitionNames.length; i++) {
   String name = beanDefinitionNames[i];
   
   AbstractBeanDefinition beanDefinition =
     (AbstractBeanDefinition) aReader.getBeanFactory()
       .getBeanDefinition(name);
   
   if (!this.preInstantiableBeans.contains(name)) {
    beanDefinition.setLazyInit(true);
   }
   
  }
 }
}

You can register this webapplication context in the web.xml (again, only development time!):

<context-param>
<param-name>contextClass</param-name>
<param-value>mypackage.LazyXmlWebApplicationContext</param-value>
</context-param>

Startup performance now increases with about 25% (avg application), have Fun!