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

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

All Implemented Interfaces:
  org.picocontainer.ComponentAdapter<T>

    public class DelegateMethodAdapter<T>

extends Object
implements org.picocontainer.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
`org.picocontainer.ComponentAdapter.NOTHING`

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

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

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

Constructor Detail

### DelegateMethodAdapter

    public DelegateMethodAdapter(Object componentKey,
                                 Object targetInstance,
                                 DelegateMethod factoryMethod)

Parameters:
  `componentKey` -
  `Component` - Implementation will be the expected return type of the factory method.

### DelegateMethodAdapter

    public DelegateMethodAdapter(Object componentKey,
                                 org.picocontainer.ComponentMonitor monitor,
                                 Object targetInstance,
                                 DelegateMethod factoryMethod)

Parameters:
  `componentKey` -
  `componentImplementation` -
  `monitor` -

Method Detail

### getComponentInstance

    public T getComponentInstance(org.picocontainer.PicoContainer container,
                                  Type into)
                           throws org.picocontainer.PicoCompositionException

  Returns the

  Specified by:
    `getComponentInstance` in interface `org.picocontainer.ComponentAdapter<T>`
  Throws:
    `org.picocontainer.PicoCompositionException`

### getDescriptor

    public String getDescriptor()

  Specified by:
    `getDescriptor` in interface `org.picocontainer.ComponentAdapter<T>`
  See Also:
    `ComponentAdapter.getDescriptor()`

### verify

    public void verify(org.picocontainer.PicoContainer container)
                throws org.picocontainer.PicoCompositionException

  Specified by:
    `verify` in interface `org.picocontainer.ComponentAdapter<T>`
  Throws:
    `org.picocontainer.PicoCompositionException`

### accept

    public void accept(org.picocontainer.PicoVisitor visitor)

  Specified by:
    `accept` in interface `org.picocontainer.ComponentAdapter<T>`

### findAdapterOfType

    public org.picocontainer.ComponentAdapter<T> findAdapterOfType(Class adapterType)

  Specified by:
    `findAdapterOfType` in interface `org.picocontainer.ComponentAdapter<T>`

### getComponentImplementation

    public Class<T> getComponentImplementation()

  Specified by:
    `getComponentImplementation` in interface `org.picocontainer.ComponentAdapter<T>`

### getComponentInstance

    @Deprecated
    public T getComponentInstance(org.picocontainer.PicoContainer container)
                           throws org.picocontainer.PicoCompositionException

  Deprecated.

  Specified by:
    `getComponentInstance` in interface `org.picocontainer.ComponentAdapter<T>`
  Throws:
    `org.picocontainer.PicoCompositionException`

### getComponentKey

    public Object getComponentKey()

  Specified by:
    `getComponentKey` in interface `org.picocontainer.ComponentAdapter<T>`

### getDelegate

    public org.picocontainer.ComponentAdapter<T> getDelegate()

  No delegates.

  Specified by:
    `getDelegate` in interface `org.picocontainer.ComponentAdapter<T>`

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