// $Id: CrConsiderSingleton.java 14127 2008-02-18 18:37:28Z tfmorris $
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package org.argouml.pattern.cognitive.critics;
import java.util.Iterator;
import org.argouml.cognitive.Designer;
import org.argouml.cognitive.ToDoItem;
import org.argouml.model.Model;
import org.argouml.uml.cognitive.UMLDecision;
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».<p>
* <p>
* see the ArgoUML User Manual: Consider Using Singleton Pattern for Class
*
* @author jrobbins
*/
public class CrConsiderSingleton extends CrUML {
/**
* Constructor for the critic.<p>
*
* 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() {
setupHeadAndDesc();
addSupportedDecision(UMLDecision.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.<p>
*
* First check we are already a Singleton.<p>
*
* Otherwise plausible candidates for the Singleton design pattern are
* classes with no instance variables (i.e. non-static attributes) and no
* outgoing associations.<p>
*
* @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}.
*/
@Override
public boolean predicate2(Object dm, Designer dsgr) {
// Only look at classes...
if (!(Model.getFacade().isAClass(dm))) {
return NO_PROBLEM;
}
// and not association classes
if (Model.getFacade().isAAssociationClass(dm)) {
return NO_PROBLEM;
}
// with a name...
if (Model.getFacade().getName(dm) == null
|| "".equals(Model.getFacade().getName(dm))) {
return NO_PROBLEM;
}
// ... and not incompletely imported
if (!(Model.getFacade().isPrimaryObject(dm))) {
return NO_PROBLEM;
}
// abstract classes are hardly ever singletons
if (Model.getFacade().isAbstract(dm)) {
return NO_PROBLEM;
}
// Check for Singleton stereotype, uninitialised instance variables and
// outgoing associations, as per JavaDoc above.
if (Model.getFacade().isSingleton(dm)) {
return NO_PROBLEM;
}
if (Model.getFacade().isUtility(dm)) {
return NO_PROBLEM;
}
// If there is an attribute which is not static => no problem
Iterator iter = Model.getFacade().getAttributes(dm).iterator();
while (iter.hasNext()) {
if (!Model.getFacade().isStatic(iter.next())) {
return NO_PROBLEM;
}
}
// If there is an outgoing association => no problem
Iterator ends = Model.getFacade().getAssociationEnds(dm).iterator();
while (ends.hasNext()) {
Iterator otherends =
Model.getFacade()
.getOtherAssociationEnds(ends.next()).iterator();
while (otherends.hasNext()) {
if (Model.getFacade().isNavigable(otherends.next())) {
return NO_PROBLEM;
}
}
}
return PROBLEM_FOUND;
}
/**
* The UID.
*/
private static final long serialVersionUID = -178026888698499288L;
}