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package ca.ubc.cs.spl.aspectPatterns.patternLibrary;
/* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* This file is part of the design patterns project at UBC
*
* The contents of this file are subject to the Mozilla Public License
* Version 1.1 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
* either https://www.mozilla.org/MPL/ or https://aspectj.org/MPL/.
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is ca.ubc.cs.spl.aspectPatterns.
*
* For more details and the latest version of this code, please see:
* https://www.cs.ubc.ca/labs/spl/projects/aodps.html
*
* Contributor(s):
*/
import java.util.Enumeration;
import java.util.WeakHashMap;
import java.util.Vector;
/**
* Defines the abstract Composite design pattern.<p>
*
* It maintains the mapping between composites and their children, defines the
* Component, Composite, and Leaf roles, and implements facilities to
* implements methods that work on the whole aggregate structure.
*
* <p><i>This is the AspectJ version.</i><p>
*
* Each concrete subaspect does the following things: <UL>
* <LI> Defines which classes are Components and Leafs
* <LI> (optional) Defines methods that operate on the whole aggregate
* structure (using visitors)
* </UL>
*
* @author Jan Hannemann
* @author Gregor Kiczales
* @version 1.1, 02/06/04
*/
public abstract aspect CompositeProtocol {
/**
* Defines the Component role. The role is public to allow clients to
* handle objects of that type.
*/
public interface Component {}
/**
* Defines the Composite role. Composites are Components that can have
* children. This role is only used within the pattern context, thus it
* is protected.
*/
protected interface Composite extends Component {}
/**
* Defines the Leaf role. Leafs are Components that can not have
* children. This role is only used within the pattern context, thus it
* is protected.
*/
protected interface Leaf extends Component {}
/**
* stores the mapping between components and their children
*/
private WeakHashMap perComponentChildren = new WeakHashMap();
/**
* Returns a vector of the children of the argument component
*/
private Vector getChildren(Component s) {
Vector children = (Vector)perComponentChildren.get(s);
if ( children == null ) {
children = new Vector();
perComponentChildren.put(s, children);
}
return children;
}
/**
* Client-accessible method to add a new child to a composite
*
* @param composite the composite to add a new child to
* @param component the new child to add
*/
public void addChild(Composite composite, Component component) {
getChildren(composite).add(component);
}
/**
* Client-accessible method to remove a child from a composite
*
* @param composite the composite to remove a child from
* @param component the child to remove
*/
public void removeChild(Composite composite, Component component) {
getChildren(composite).remove(component);
}
/**
* Client-accessible method to get an Enumeration of all children of
* a composite
*
* @param composite the composite to add a new child to
* @param component the new child to add
*/
public Enumeration getAllChildren(Component c) {
return getChildren(c).elements();
}
/**
* Defines an interface for visitors that operate on the composite
* structure. These visitors are implemented by concrete sub-aspects
* and used in the <code>recurseOperation(Component, Visitor)</code>
* method. This construct is needed to allow for method forwarding:
* A composite that receives a method forwards the request to all its
* children.
*/
protected interface Visitor {
/**
* Generic method that performs an unspecified operation on compoennts
*
* @param c the component to perform the operation on
*/
public void doOperation(Component c);
}
/**
* Implements the method-forwarding logic: If a method is to be applied
* to the aggregate structure, each composite forwards it to its children
*
* @param c the current component
* @param v the visitor representing the operation to be performed
*/
public void recurseOperation(Component c, Visitor v) { // This implements the logic that Composites forward
for (Enumeration enum = getAllChildren(c); enum.hasMoreElements(); ) { // method calls to their children
Component child = (Component) enum.nextElement();
v.doOperation(child);
}
}
/**
* Defines an interface for visitors that operate on the composite
* structure. These visitors are implemented by comcrete sub-aspects
* and used in the <code>recurseOperation(Component, Visitor)<>/code>
* method. This construct is needed to allow for method forwarding:
* A composite that receives a method forwards the request to all its
* children. <p>
*
* This version allows for a return value of Object type. For some odd
* reason AJDT complains if this type is declared protected (as it should
* be). Note that Visitor above works fine as protected.
*/
public interface FunctionVisitor {
/**
* Generic method that performs an unspecified operation on components
*
* @param c the component to perform the operation on
*/
public Object doFunction(Component c);
}
/**
* Implements the method-forwarding logic: If a method is to be applied
* to the aggregate structure, each composite forwards it to its children.
* This version allows for a return value of Object type, effectively
* enableing collecting aggregate results on the composite structure.
*
* @param c the current component
* @param fv the visitor representing the operation to be performed
*/
public Enumeration recurseFunction(Component c, FunctionVisitor fv) {
Vector results = new Vector();
for (Enumeration enum = getAllChildren(c); enum.hasMoreElements(); ) { // method calls to their children
Component child = (Component) enum.nextElement();
results.add(fv.doFunction(child));
}
return results.elements();
}
}
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