NameSpaceTranslatorFactory.java

/* (c) 2014 Open Source Geospatial Foundation - all rights reserved
 * (c) 2001 - 2013 OpenPlans
 * This code is licensed under the GPL 2.0 license, available at the root
 * application directory.
 */
package org.geoserver.wfs.xml;

import java.lang.reflect.Constructor;
import java.util.HashMap;
import java.util.Map;


/**
 * NameSpaceTranslatorFactory purpose.
 * <p>
 * Follows the factory pattern. Creates and stores a list of name space translators.
 * </p>
 * @see NameSpaceTranslator
 * @author dzwiers, Refractions Research, Inc.
 * @author $Author: dmzwiers $ (last modification)
 * @version $Id$
 */
public class NameSpaceTranslatorFactory {
    /** map of namespace names as Strings -> Class representations of NameSpaceTranslators */
    private Map namespaceTranslators;

    /** map of prefixs as String -> Instances of NameSpaceTranslators */
    private Map namespaceTranslatorInstances;

    /** the only instance */
    private final static NameSpaceTranslatorFactory instance = new NameSpaceTranslatorFactory();

    /**
     * NameSpaceTranslatorFactory constructor.
     * <p>
     * Loads some default prefixes into memory when the class is first loaded.
     * </p>
     *
     */
    private NameSpaceTranslatorFactory() {
        namespaceTranslators = new HashMap();
        namespaceTranslatorInstances = new HashMap();

        //TODO replace null for these default namespaces.
        namespaceTranslators.put("http://www.w3.org/2001/XMLSchema", XMLSchemaTranslator.class);
        namespaceTranslators.put("http://www.opengis.net/gml", GMLSchemaTranslator.class);

        addNameSpaceTranslator("xs", "http://www.w3.org/2001/XMLSchema");
        addNameSpaceTranslator("xsd", "http://www.w3.org/2001/XMLSchema");
        addNameSpaceTranslator("gml", "http://www.opengis.net/gml");
    }

    /**
     * getInstance purpose.
     * <p>
     * Completes the singleton pattern of this factory class.
     * </p>
     * @return NameSpaceTranslatorFactory The instance.
     */
    public static NameSpaceTranslatorFactory getInstance() {
        return instance;
    }

    /**
     * addNameSpaceTranslator purpose.
     * <p>
     * Adds a new translator for the namespace specified if a
     * NameSpaceTranslator was registered for that namespace.
     * </p>
     * <p>
     * Some the magic for creating instances using the classloader occurs here
     * (ie. the translators are not loaded lazily)
     * </p>
     * @param prefix The desired namespace prefix
     * @param namespace The desired namespace.
     */
    public void addNameSpaceTranslator(String prefix, String namespace) {
        if ((prefix == null) || (namespace == null)) {
            throw new NullPointerException();
        }

        try {
            Class nstClass = (Class) namespaceTranslators.get(namespace);

            if (nstClass == null) {
                return;
            }

            Constructor nstConstructor = nstClass.getConstructor(new Class[] { String.class, });
            NameSpaceTranslator nst = (NameSpaceTranslator) nstConstructor.newInstance(new Object[] {
                        prefix,
                    });
            namespaceTranslatorInstances.put(prefix, nst);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * getNameSpaceTranslator purpose.
     * <p>
     * Description ...
     * </p>
     * @param prefix the prefix of the translator to get.
     * @return the translator, or null if it was not found
     */
    public NameSpaceTranslator getNameSpaceTranslator(String prefix) {
        return (NameSpaceTranslator) namespaceTranslatorInstances.get(prefix);
    }

    /**
     * registerNameSpaceTranslator purpose.
     * <p>
     * Registers a namespace and it's translator with the factory. good for adding additional namespaces :)
     * </p>
     * @param namespace The namespace.
     * @param nameSpaceTranslator The translator class for this namespace.
     */
    public void registerNameSpaceTranslator(String namespace, Class nameSpaceTranslator) {
        if ((nameSpaceTranslator != null)
                && NameSpaceTranslator.class.isAssignableFrom(nameSpaceTranslator)) {
            namespaceTranslators.put(namespace, nameSpaceTranslator);
        }
    }
}