[jboss-dev-forums] [Design the new POJO MicroContainer] - Lazy bean behaviour

[alesj]

I'm doing (apart from AS5_PS ... no worries ;-)) some GUI example console for MC and was missing the following feature - lazy 'instantiation/install' of the bean.

e.g. I have some service that has many dependencies - many injected beans. One of them is rarely used and/or is fully installed in some later-on deployment unit. But I would still like to have that first service up and running.

So, I hacked a lazy notion to our beans - lazy proxies.

What you can do now is the following XML

  |    <bean name="bean" class="org.jboss.test.kernel.lazy.support.RareBean"/>
  | 
  |    <lazy name="proxy" bean="bean" exposeClass="true">
  |       <interface>org.jboss.test.kernel.lazy.support.IRare</interface>
  |    </lazy>
  | 

or the straight API


  |       AbstractLazyMetaData lazy = new AbstractLazyMetaData("bean");
  |       lazy.setInterfaces(Collections.singleton(IRare.class.getName()));
  | 

And the test to show that lazyness :-)

  |       AbstractBeanMetaData bean = new AbstractBeanMetaData("bean", RareBean.class.getName());
  |       bean.setMode(ControllerMode.MANUAL);
  | 
  |       KernelControllerContext beanContext = controller.install(bean);
  |       controller.change(beanContext, ControllerState.NOT_INSTALLED);
  | 
  |       ModifiedLazyMetaData lazy = new ModifiedLazyMetaData("bean", getFactoryClassName());
  |       lazy.setInterfaces(Collections.singleton(IRare.class.getName()));
  |       KernelControllerContext lazyContext = controller.install(lazy);
  | 
  |       assertNotNull(lazyContext);
  |       assertEquals(ControllerState.DESCRIBED, lazyContext.getState());
  | 
  |       controller.change(beanContext, ControllerState.DESCRIBED);
  |       controller.change(lazyContext, ControllerState.INSTALLED);
  | 
  |       IRare lazyRare = (IRare)lazyContext.getTarget();
  |       assertNotNull(lazyRare);
  | 
  |       try
  |       {
  |          lazyRare.getHits();
  |          throw new RuntimeException("Should not be here.");
  |       }
  |       catch(Throwable t)
  |       {
  |          assertInstanceOf(t, IllegalArgumentException.class);
  |       }
  | 
  |       controller.change(beanContext, ControllerState.INSTALLED);
  | 
  |       assertEquals(0, lazyRare.getHits());
  |       lazyRare.setHits(10);
  |       assertEquals(5, lazyRare.checkHits(15));
  | 

The code checks for the first available proxy generator - Javassist, JBossAOP (wip), JDK, ... (possible additions CGLIB, ASM, ...)

  |    static
  |    {
  |       initializerMap = new LinkedHashMap<String, String>();
  |       // test class name, actual LazyInitializer implementation
  |       initializerMap.put("javassist.util.proxy.ProxyObject", "org.jboss.kernel.plugins.lazy.JavassistLazyInitializer");
  |       initializerMap.put("org.jboss.aop.proxy.container.AOPProxyFactoryParameters", "org.jboss.aop.microcontainer.lazy.JBossAOPLazyInitializer");
  |       initializerMap.put("java.lang.reflect.Proxy", "org.jboss.kernel.plugins.lazy.JDKLazyInitializer");
  |    }
  | 
  |    /**
  |     * Get the LazyInitializater instance.
  |     *
  |     * @param configurator the configurator
  |     * @return initializer instance
  |     */
  |    protected static LazyInitializer getInitializer(KernelConfigurator configurator)
  |    {
  |       if (initializer == null)
  |       {
  |          for(Map.Entry<String, String> entry : initializerMap.entrySet())
  |          {
  |             if (testLibExists(entry.getKey()))
  |             {
  |                initializer = createInitializer(configurator, entry.getValue());
  |                if (initializer != null)
  |                   break;
  |             }
  |          }
  |       }
  |       if (initializer == null)
  |          throw new IllegalArgumentException("Cannot initialize LazyInitializater, check classpath for missing classes.");
  |       return initializer;
  |    }
  | 

The proxies use KernelBus to do the invocation.

Currently you need to specify which interfaces are exposed.
Perhaps this can be done automa(g|t)ically?

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