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XMLTooling-J is a low-level library that may be used to construct libraries that allow developers to work with XML in a Java beans manner.
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/*
 * Licensed to the University Corporation for Advanced Internet Development, 
 * Inc. (UCAID) under one or more contributor license agreements.  See the 
 * NOTICE file distributed with this work for additional information regarding
 * copyright ownership. The UCAID licenses this file to You under the Apache 
 * License, Version 2.0 (the "License"); you may not use this file except in 
 * compliance with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.opensaml.xml.io;

import java.util.Collections;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import javax.xml.namespace.QName;

import org.opensaml.xml.util.XMLHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.w3c.dom.Element;

/**
 * This thread-safe factory creates {@link org.opensaml.xml.io.Unmarshaller}s that can be used to convert W3C DOM
 * elements into {@link org.opensaml.xml.XMLObject}s. Unmarshallers are stored and retrieved by a
 * {@link javax.xml.namespace.QName} key. This key is either the XML Schema Type or element QName of the XML element
 * being unmarshalled.
 */
public class UnmarshallerFactory {

    /** Class logger. */
    private final Logger log = LoggerFactory.getLogger(UnmarshallerFactory.class);

    /** Map of unmarshallers to the elements they are for. */
    private Map unmarshallers;

    /**
     * Constructor.
     */
    public UnmarshallerFactory() {
        unmarshallers = new ConcurrentHashMap();
    }

    /**
     * Gets the Unmarshaller for a particular element or null if no unmarshaller is registered for an element.
     * 
     * @param key the key the unmarshaller was registered under
     * 
     * @return the Unmarshaller
     */
    public Unmarshaller getUnmarshaller(QName key) {
        if (key == null) {
            return null;
        }

        return unmarshallers.get(key);
    }

    /**
     * Retrieves the unmarshaller for the given element. The schema type, if present, is tried first as the key with the
     * element QName used if no schema type is present or does not have a unmarshaller registered under it.
     * 
     * @param domElement the element to retrieve the unmarshaller for
     * 
     * @return the unmarshaller for the XMLObject the given element can be unmarshalled into
     */
    public Unmarshaller getUnmarshaller(Element domElement) {
        Unmarshaller unmarshaller;

        unmarshaller = getUnmarshaller(XMLHelper.getXSIType(domElement));

        if (unmarshaller == null) {
            unmarshaller = getUnmarshaller(XMLHelper.getNodeQName(domElement));
        }

        return unmarshaller;
    }

    /**
     * Gets an immutable listing of all the Unarshallers currently registered.
     * 
     * @return a listing of all the Unmarshallers currently registered
     */
    public Map getUnmarshallers() {
        return Collections.unmodifiableMap(unmarshallers);
    }

    /**
     * Registers an Unmarshaller with this factory. If an Unmarshaller exist for the Qname given it is replaced with the
     * given unmarshaller.
     * 
     * @param key the key the unmarshaller was registered under
     * @param unmarshaller the Unmarshaller
     */
    public void registerUnmarshaller(QName key, Unmarshaller unmarshaller) {
        log.debug("Registering unmarshaller, {}, for object type, {}", unmarshaller.getClass().getName(), key);
        if (key == null) {
            throw new IllegalArgumentException("Unmarshaller key may not be null");
        }
        unmarshallers.put(key, unmarshaller);
    }

    /**
     * Deregisters the unmarshaller for the given element.
     * 
     * @param key the key the unmarshaller was registered under
     * 
     * @return the Unmarshaller previously registered or null
     */
    public Unmarshaller deregisterUnmarshaller(QName key) {
        log.debug("Deregistering marshaller for object type {}", key);
        if (key != null) {
            return unmarshallers.remove(key);
        }

        return null;
    }
}