DelegateMethodAdapter (PicoContainer Gems 2.10 API)

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org.picocontainer.gems.adapters
Class DelegateMethodAdapter<T>

java.lang.Object
  org.picocontainer.gems.adapters.DelegateMethodAdapter<T>

All Implemented Interfaces:: ComponentAdapter<T>

public class DelegateMethodAdapter<T>
extends Object
implements ComponentAdapter<T>
extends Object
implements ComponentAdapter<T>

Object construction is sometimes expensive, especially when it is seldom used object. The goal of this adapter is to use the DelegateMethod type to allow delayed construction of objects.

For example, in a web application, to be able to have classes that depend on the HttpSession object, you would have to call HttpServletRequest.getSession(true). This is fine unless you don't want to create a session until you absolutely have to.

Enter DelegateMethodAdapter:

 //Assumed Variables: request == HttpServletRequest.
 //Typical PicoContainer
 MutablePicoContainer pico = new PicoBuilder().withLifecycle().withCaching()
                .build();
 
 //Create a delegate method that will invoke HttpServletRequest.getSession(true) when invoke() is called.
 DelegateMethod delegateMethod = new DelegateMethod(HttpServletRequest.class,
                "getSession", true);
 
 //Create the Adapter wrapping the delegate method.  
 DelegateMethodAdapter methodAdapter = new DelegateMethodAdapter(
                HttpSession.class, request, delegateMethod);
 pico.addAdapter(methodAdapter);
 
 //If only executing this code, the HttpSession should not be created yet.
 assertNull(request.getSession(false));
 
 //Will get the session object by having the delegate method call HttpServletRequest.getSession(true)
 HttpSession session = pico.getComponent(HttpSession.class);
 assertNotNull(session);
 
 //Should demonstrate that the session has now been created.
 assertNotNull(request.getSession(false));

With an adapter like this, you can write classes like:

 public class SessionUser {
        public SessionUser(HttpSession session) {
                //.....
        }
 }

With impunity, and are guaranteed that the session would not be created unless the SessionUser object was constructed.

Author:: Michael Rimov

Nested Class Summary

Nested classes/interfaces inherited from interface org.picocontainer.ComponentAdapter
`ComponentAdapter.NOTHING`

Constructor Summary
`DelegateMethodAdapter(Object componentKey, ComponentMonitor monitor, Object targetInstance, DelegateMethod factoryMethod)`
`DelegateMethodAdapter(Object componentKey, Object targetInstance, DelegateMethod factoryMethod)`

Method Summary
`void`	`accept(PicoVisitor visitor)`
`ComponentAdapter<T>`	`findAdapterOfType(Class adapterType)`
`Class<T>`	`getComponentImplementation()`
`T`	`getComponentInstance(PicoContainer container)` Deprecated.
`T`	`getComponentInstance(PicoContainer container, Type into)` Returns the
`Object`	`getComponentKey()`
`ComponentAdapter<T>`	`getDelegate()` No delegates.
`String`	`getDescriptor()`
`void`	`verify(PicoContainer container)`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail