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/**
 * SCA4J
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 * Licensed to you under the Apache License, Version 2.0 (the "License"); you may
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 * is included in this distrubtion or you may obtain a copy at
 *
 *    http://www.opensource.org/licenses/apache2.0.php
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 * Unless required by applicable law or agreed to in writing, software distributed
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 * CONDITIONS OF ANY KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations under the License.
 *
 * This project contains code licensed from the Apache Software Foundation under
 * the Apache License, Version 2.0 and original code from project contributors.
 *
 *
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 * Copyright (c) 2007 - 2008 fabric3 project contributors
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 * Licensed to you under the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.  A copy of the license
 * is included in this distrubtion or you may obtain a copy at
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 *    http://www.opensource.org/licenses/apache2.0.php
 *
 * 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.
 *
 * This project contains code licensed from the Apache Software Foundation under
 * the Apache License, Version 2.0 and original code from project contributors.
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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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
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 *   http://www.apache.org/licenses/LICENSE-2.0
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 * Unless required by applicable law or agreed to in writing,
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package org.sca4j.loader.impl;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;

import javax.xml.namespace.QName;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;

import org.oasisopen.sca.annotation.EagerInit;
import org.oasisopen.sca.annotation.Reference;
import org.sca4j.introspection.IntrospectionContext;
import org.sca4j.introspection.xml.LoaderException;
import org.sca4j.introspection.xml.LoaderRegistry;
import org.sca4j.introspection.xml.TypeLoader;
import org.sca4j.introspection.xml.UnrecognizedElementException;
import org.sca4j.services.xmlfactory.XMLFactory;

/**
 * The default implementation of a loader registry
 *
 * @version $Rev: 4301 $ $Date: 2008-05-23 06:33:58 +0100 (Fri, 23 May 2008) $
 */
@EagerInit
public class LoaderRegistryImpl implements LoaderRegistry {
    private Monitor monitor;
    private final XMLInputFactory xmlFactory;
    private Map> mappedLoaders;
    private final Map> loaders = new HashMap>();

    public LoaderRegistryImpl(@org.sca4j.api.annotation.Monitor Monitor monitor, @Reference XMLFactory factory) {
        this.monitor = monitor;
        this.xmlFactory = factory.newInputFactoryInstance();
    }

    @Reference(required = false)
    public void setLoaders(Map> mappedLoaders) {
        this.mappedLoaders = mappedLoaders;
    }

    public void registerLoader(QName element, TypeLoader loader) {
        if (loaders.containsKey(element)) {
            throw new IllegalStateException("Loader already registered for " + element);
        }
        monitor.registeringLoader(element);
        loaders.put(element, loader);
    }

    public void unregisterLoader(QName element) {
        monitor.unregisteringLoader(element);
        loaders.remove(element);
    }

    public  O load(XMLStreamReader reader, Class type, IntrospectionContext introspectionContext)
            throws XMLStreamException, UnrecognizedElementException {
        QName name = reader.getName();
        monitor.elementLoad(name);
        TypeLoader loader = loaders.get(name);
        if (loader == null) {
            loader = mappedLoaders.get(name);
        }
        if (loader == null) {
            throw new UnrecognizedElementException(reader);
        }
        return type.cast(loader.load(reader, introspectionContext));
    }

    public  O load(URL url, Class type, IntrospectionContext ctx) throws LoaderException {
        InputStream stream;
        try {
            stream = url.openStream();
        } catch (IOException e) {
            throw new LoaderException("Invalid URL: " + url.toString(), e);
        }
        try {
            try {
                return load(url, stream, type, ctx);
            } catch (XMLStreamException e) {
                throw new LoaderException("Invalid URL: " + url.toString(), e);
            }
        } finally {
            try {
                stream.close();
            } catch (IOException e) {
                // ignore
            }
        }
    }

    private  O load(URL url, InputStream stream, Class type, IntrospectionContext ctx) throws XMLStreamException, UnrecognizedElementException {
        XMLStreamReader reader;
        reader = xmlFactory.createXMLStreamReader(url.toString(), stream);

        try {
            reader.nextTag();
            return load(reader, type, ctx);
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (XMLStreamException e) {
                    // ignore
                }
            }
        }
    }

    public static interface Monitor {
        /**
         * Event emitted when a StAX element loader is registered.
         *
         * @param xmlType the QName of the element the loader will handle
         */
        void registeringLoader(QName xmlType);

        /**
         * Event emitted when a StAX element loader is unregistered.
         *
         * @param xmlType the QName of the element the loader will handle
         */
        void unregisteringLoader(QName xmlType);

        /**
         * Event emitted when a request is made to load an element.
         *
         * @param xmlType the QName of the element that should be loaded
         */
        void elementLoad(QName xmlType);
    }
}