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// $Id: CrConsiderSingleton.java,v 1.20 2004/09/21 19:03:29 mvw Exp $
// Copyright (c) 1996-2003 The Regents of the University of California. All
// Rights Reserved. Permission to use, copy, modify, and distribute this
// software and its documentation without fee, and without a written
// agreement is hereby granted, provided that the above copyright notice
// and this paragraph appear in all copies.  This software program and
// documentation are copyrighted by The Regents of the University of
// California. The software program and documentation are supplied "AS
// IS", without any accompanying services from The Regents. The Regents
// does not warrant that the operation of the program will be
// uninterrupted or error-free. The end-user understands that the program
// was developed for research purposes and is advised not to rely
// exclusively on the program for any reason.  IN NO EVENT SHALL THE
// UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT,
// SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS,
// ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
// THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE. THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY
// WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
// PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
// CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT,
// UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

// File: CrConsiderSingleton.java
// Classes: CrConsiderSingleton
// Original Author: jrobbins@ics.uci.edu

package org.argouml.pattern.cognitive.critics;

import java.util.Iterator;
import org.argouml.cognitive.Designer;
import org.argouml.cognitive.ToDoItem;
import org.argouml.model.ModelFacade;


// Use Model through ModelFacade.
import org.argouml.uml.cognitive.critics.CrUML;

/**
 * 

A critic to detect when a class can never have more than one instance (of * itself of any subclasses), and thus whether it is suitable for declaration * as a Singleton (with stereotype «Singleton».

* * @see * ArgoUML User Manual: Singleton Violated */ public class CrConsiderSingleton extends CrUML { /** *

Constructor for the critic.

* *

Sets up the resource name, which will allow headline and description * to be found for the current locale. Provides a design issue category * (PATTERNS), sets a priority for any to-do items (LOW) and adds triggers * for metaclasses "stereotype", "structuralFeature" and * "associationEnd".

*/ public CrConsiderSingleton() { setResource("CrConsiderSingleton"); addSupportedDecision(CrUML.DEC_PATTERNS); setPriority(ToDoItem.LOW_PRIORITY); // These may not actually make any difference at present (the code // behind addTrigger needs more work). addTrigger("stereotype"); addTrigger("structuralFeature"); addTrigger("associationEnd"); } /** *

The trigger for the critic.

* *

First check we are already a Singleton.

* *

Otherwise plausible candidates for the Singleton design pattern are * classes with no instance variables (i.e. non-static attributes) and no * outgoing associations.

* * @param dm the {@link java.lang.Object Object} to be checked against * the critic. * * @param dsgr the {@link org.argouml.cognitive.Designer Designer} * creating the model. Not used, this is for future * development of ArgoUML. * * @return {@link #PROBLEM_FOUND PROBLEM_FOUND} if the critic is * triggered, otherwise {@link #NO_PROBLEM NO_PROBLEM}. */ public boolean predicate2(Object dm, Designer dsgr) { // Only look at classes... if (!(ModelFacade.isAClass(dm))) { return NO_PROBLEM; } // with a name... if (ModelFacade.getName(dm) == null || "".equals(ModelFacade.getName(dm))) { return NO_PROBLEM; } // ... and not incompletely imported if (!(ModelFacade.isPrimaryObject(dm))) return NO_PROBLEM; // abstract classes are hardly ever singletons if (ModelFacade.isAbstract(dm)) return NO_PROBLEM; // Check for Singleton stereotype, uninitialised instance variables and // outgoing associations, as per JavaDoc above. if (ModelFacade.isSingleton(dm)) { return NO_PROBLEM; } if (ModelFacade.isUtility(dm)) { return NO_PROBLEM; } // If there is an attribute with instance scope => no problem Iterator iter = ModelFacade.getAttributes(dm).iterator(); while (iter.hasNext()) { if (ModelFacade.isInstanceScope(iter.next())) return NO_PROBLEM; } // If there is an outgoing association => no problem Iterator ends = ModelFacade.getAssociationEnds(dm).iterator(); while (ends.hasNext()) { Iterator otherends = ModelFacade.getOtherAssociationEnds(ends.next()).iterator(); while (otherends.hasNext()) { if (ModelFacade.isNavigable(otherends.next())) return NO_PROBLEM; } } return PROBLEM_FOUND; } } /* end class CrConsiderSingleton */

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