Filter projects based on criteria. Uses a filterable Iterator with custom predicate, regexps and reflection.

filter.java

/**
 * List projects based on criteria.
 * @param action
 * @param user
 */
public Iterable<IProject> executeAction(ListProjectsAction action, IUser user) {
	Iterable<IProject> items = projects.values();
	
	if(action.getParams().containsKey("filter")){
		Pattern pattern = Pattern.compile(Pattern.quote(action.getParam("pattern"))
				.replace("*", "\\E.*\\Q")
				.replace("?", "\\E.?\\Q"));
		IFilterPredicate<IProject> predicate = null;
		try {
			switch (action.getParam("filter")) {
			case "type":
				predicate = new RegexpPropertyGetterPredicate(pattern, AbstractProject.class.getMethod("getType"));
				break;
			case "language":
				predicate = new RegexpPropertyGetterPredicate(pattern, AbstractProject.class.getMethod("getLang"));
				break;
			case "client":
				predicate = new RegexpPropertyGetterPredicate(pattern, AbstractProject.class.getMethod("getClient"));
				break;
			default:
				break;
			}
		} catch (NoSuchMethodException | SecurityException e) {}
		
		items = new FilterIterator<>(items, predicate);
	}
	
	return items;
}


// ............


private class RegexpPropertyGetterPredicate implements IFilterPredicate<IProject> {
		
	private Pattern pattern;
	private Method propertyGetter;
		
	public RegexpPropertyGetterPredicate(Pattern pattern, Method propertyGetter){
		this.pattern = pattern;
		this.propertyGetter = propertyGetter;
	}

	public boolean eval(IProject project) {
		try {
			return pattern.matcher((String) propertyGetter.invoke(project)).matches();
		} catch (InvocationTargetException | IllegalAccessException | IllegalArgumentException e) {
			return false;
		}
	}
		
}