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PicketLink Common Code
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/*
 * JBoss, Home of Professional Open Source
 *
 * Copyright 2013 Red Hat, Inc. and/or its affiliates.
 *
 * Licensed 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.picketlink.common.parsers;

import java.io.InputStream;

import javax.xml.stream.EventFilter;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.Characters;
import javax.xml.stream.events.XMLEvent;

import org.picketlink.common.PicketLinkLogger;
import org.picketlink.common.PicketLinkLoggerFactory;
import org.picketlink.common.exceptions.ParsingException;
import org.picketlink.common.util.StaxParserUtil;

/**
 * Base class for parsers
 *
 * @author [email protected]
 * @since Oct 12, 2010
 */
public abstract class AbstractParser implements ParserNamespaceSupport {
    
    protected static final PicketLinkLogger logger = PicketLinkLoggerFactory.getLogger();
    
    /**
     * Parse an InputStream for payload
     *
     * @param configStream
     * @return
     * @throws {@link IllegalArgumentException}
     * @throws {@link IllegalArgumentException} when the configStream is null
     */
    public Object parse(InputStream configStream) throws ParsingException {
        if (configStream == null)
            throw logger.nullArgumentError("InputStream");

        XMLInputFactory xmlInputFactory = XMLInputFactory.newInstance();

        XMLEventReader xmlEventReader = StaxParserUtil.getXMLEventReader(configStream);

        try {
            xmlEventReader = xmlInputFactory.createFilteredReader(xmlEventReader, new EventFilter() {
                public boolean accept(XMLEvent xmlEvent) {
                    // We are going to disregard characters that are new line and whitespace
                    if (xmlEvent.isCharacters()) {
                        Characters chars = xmlEvent.asCharacters();
                        String data = chars.getData();
                        data = valid(data) ? data.trim() : null;
                        return valid(data);
                    } else {
                        return xmlEvent.isStartElement() || xmlEvent.isEndElement();
                    }
                }

                private boolean valid(String str) {
                    return str != null && str.length() > 0;
                }
            });
        } catch (XMLStreamException e) {
            throw logger.parserException(e);
        }

        return parse(xmlEventReader);
    }

}