HUDFactory.java

package games.fighter.davidalan.util;

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;
import java.util.Observable;

import vooga.fighter.view.HUDElement;

/**
 * Contains a single static method to reflect on Observable objects and produce
 * HUDElements in conjunction with HUDVariable annotations on class members.
 * This class should not require instantiation.
 * 
 * @author Wayne You
 * 
 */
public class HUDFactory {
    private static final String DEFAULT_PACKAGE = "vooga.fighter.view";
    
    /**
     * Generate a list of HUDElements based off of annotations of member
     * variables in the
     * given Observable object. Assumes vooga.fighter.view package.
     * 
     * @param gameObject
     *            The Observable object with potentially annotated member
     *            variables.
     * @return A List of HUDElements
     * @throws InstantiationException
     * @throws IllegalAccessException
     * @throws ClassNotFoundException
     */
    public static List<HUDElement> getHUDElements(Observable gameObject)
            throws InstantiationException, IllegalAccessException,
            ClassNotFoundException {
        return getHUDElements(gameObject, DEFAULT_PACKAGE);
    }
    
    /**
     * Generate a list of HUDElements based off of annotations of member
     * variables in the
     * given Observable object. Defaults to vooga package on failure.
     * 
     * @param gameObject
     *            The Observable object with potentially annotated member
     *            variables.
     * @param packageName
     *            The name of the package with the HUDElements in use.
     * @return A List of HUDElements
     * @throws InstantiationException
     * @throws IllegalAccessException
     * @throws ClassNotFoundException
     */
    public static List<HUDElement> getHUDElements(Observable gameObject,
            String packageName) throws InstantiationException,
            IllegalAccessException, ClassNotFoundException {
        @SuppressWarnings("rawtypes")
        Class objectClass = gameObject.getClass();
        
        ArrayList<HUDElement> elements = new ArrayList<HUDElement>();
        
        for (Field member : objectClass.getDeclaredFields()) {
            for (Annotation a : member.getAnnotations()) {
                if (a instanceof HUDVariable) {
                    HUDVariable varAnnotation = (HUDVariable) a;
                    member.setAccessible(true);
                    if (member.get(gameObject) == null) {
                        continue;
                    }
                    HUDElement newElement;
                    try {
                        String subclass = packageName + ".HUD"
                                + varAnnotation.HUDElementClass();
                        newElement = (HUDElement) Class.forName(subclass)
                                .newInstance();
                    }
                    catch (InstantiationException e) {
                        // Attempt to default to the vooga package if the given
                        // package fails.
                        String subclass = DEFAULT_PACKAGE + ".HUD"
                                + varAnnotation.HUDElementClass();
                        newElement = (HUDElement) Class.forName(subclass)
                                .newInstance();
                    }
                    newElement.setName(varAnnotation.name());
                    newElement.setObservedValue(member.getName());
                    gameObject.addObserver(newElement);
                    elements.add(newElement);
                    newElement.update(gameObject, null);
                }
            }
        }
        
        return elements;
    }
}