co.codewizards.cloudstore.core.objectfactory

Interface ClassExtension<T>

Type Parameters:

T - the type of the base-class to be extended (i.e. replaced in all instantiations) by a certain sub-class.

All Known Implementing Classes:

AbstractClassExtension

public interface ClassExtension<T>

A ClassExtension declares that a sub-class must be instantiated instead of a certain base-class.

In order to register a sub-class as replacement for a certain base-class, implementors have to provide a ClassExtension and register it using the ServiceLoader-mechanism. This means, they must place a file named co.codewizards.cloudstore.core.objectfactory.ClassExtension into src/main/resources/META-INF/services/ in their extension-project and enlist their ClassExtension-implementation there.

Important: It is recommended not to directly implement this interface, but to sub-class AbstractClassExtension instead.

Important 2: If a certain base-class should be replaceable using this mechanism, all occurrences of new MyBaseClass(...) in the entire code-base must be replaced by createObject(MyBaseClass.class, ...).

Important 3: It is urgently recommended not to use this approach, whenever it is possible to use a better solution, preferably a well-defined service (=> ServiceLoader). There are situations, though, e.g. data-model-classes (a.k.a. entities), where services are not possible and ObjectFactoryUtil + ClassExtension is the perfect solution.

Author:

Marco หงุ่ยตระกูล-Schulze - marco at codewizards dot co

Method Summary

Modifier and Type	Method and Description
Class<T>	getBaseClass() Gets the base-class to be extended by instantiating a sub-class instead.
Class<? extends T>	getExtendingClass() Gets the sub-class extending the baseClass to be instantiated whenever a new instance of the base-class is requested.
int	getPriority() Gets the priority of this extension.

Method Detail

getPriority

int getPriority()

Gets the priority of this extension.

If there are multiple ClassExtension-implementations for the same baseClass, the extension with the highest priority (i.e the greatest number returned here) is chosen.

Returns:

the priority of this extension. Might be negative, 0 or positive.

getBaseClass

Class<T> getBaseClass()

Gets the base-class to be extended by instantiating a sub-class instead.

Returns:

the base-class to be replaced in all instantiations. Never null.

getExtendingClass

Class<? extends T> getExtendingClass()

Gets the sub-class extending the baseClass to be instantiated whenever a new instance of the base-class is requested.

Returns:

the sub-class to be instantiated instead of the baseClass. Never null.