# SimpleXMLFilteredEventReader.java

    /*
     * Copyright 2011, 2012 Odysseus Software GmbH
     *
     * 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.apache.synapse.commons.staxon.core.event;

    import javax.xml.stream.EventFilter;
    import javax.xml.stream.XMLEventReader;
    import javax.xml.stream.XMLStreamConstants;
    import javax.xml.stream.XMLStreamException;
    import javax.xml.stream.events.EntityReference;
    import javax.xml.stream.events.XMLEvent;
    import javax.xml.stream.util.EventReaderDelegate;

    /**
     * Simple implementation of a filtered {@link XMLEventReader}.
     */
    public class SimpleXMLFilteredEventReader extends EventReaderDelegate {
        private final EventFilter filter;

        private int currentEventType = -1;

        public SimpleXMLFilteredEventReader(XMLEventReader reader, EventFilter filter) {
            super(reader);
            this.filter = filter;
        }

        @Override
        public void setParent(XMLEventReader reader) {
            throw new UnsupportedOperationException();
        }

        @Override
        public boolean hasNext() {
            try {
                while (getParent().hasNext()) {
                    if (filter.accept(getParent().peek())) {
                        return true;
                    }
                    getParent().nextEvent();
                }
                return false;
            } catch (XMLStreamException e) {
                return false;
            }
        }

        @Override
        public XMLEvent peek() throws XMLStreamException {
            return hasNext() ? getParent().peek() : null;
        }

        @Override
        public Object next() {
            try {
                return nextEvent();
            } catch (XMLStreamException e) {
                throw new RuntimeException(e);
            }
        }

        @Override
        public XMLEvent nextEvent() throws XMLStreamException {
            if (hasNext()) {
                XMLEvent event = getParent().nextEvent();
                currentEventType = event.getEventType();
                return event;
            }
            throw new XMLStreamException("no more events");
        }

        @Override
        public String getElementText() throws XMLStreamException {
            if (currentEventType != XMLStreamConstants.START_ELEMENT) {
                throw new XMLStreamException("Expected start element event");
            }
            StringBuilder builder = null;
            String leadText = null;
            while (true) {
                XMLEvent event = nextEvent();
                String data = null;
                switch (event.getEventType()) {
                    case XMLStreamConstants.ENTITY_REFERENCE:
                        data = ((EntityReference) event).getName();
                        break;
                    case XMLStreamConstants.CDATA:
                    case XMLStreamConstants.CHARACTERS:
                        data = event.asCharacters().getData();
                        break;
                    case XMLStreamConstants.COMMENT:
                    case XMLStreamConstants.PROCESSING_INSTRUCTION:
                    case XMLStreamConstants.SPACE:
                        break;
                    case XMLStreamConstants.END_ELEMENT:
                        return builder == null ? (leadText == null ? "" : leadText) : builder.toString();
                    default:
                        throw new XMLStreamException("Unexpected event type " + currentEventType, event.getLocation());
                }
                if (data != null) {
                    if (leadText == null) { // first event?
                        leadText = data;
                    } else {
                        if (builder == null) { // second event?
                            builder = new StringBuilder(leadText);
                        }
                        builder.append(data);
                    }
                }
            }
        }

        @Override
        public XMLEvent nextTag() throws XMLStreamException {
            while (true) {
                XMLEvent event = nextEvent();
                switch (event.getEventType()) {
                    case XMLStreamConstants.START_DOCUMENT:
                        break;
                    case XMLStreamConstants.COMMENT:
                    case XMLStreamConstants.PROCESSING_INSTRUCTION:
                    case XMLStreamConstants.SPACE:
                        break;
                    case XMLStreamConstants.CDATA:
                    case XMLStreamConstants.CHARACTERS:
                        if (!event.asCharacters().isWhiteSpace()) {
                            throw new XMLStreamException("Encountered non-whitespace text");
                        }
                        break;
                    case XMLStreamConstants.START_ELEMENT:
                    case XMLStreamConstants.END_ELEMENT:
                        return event;
                    default:
                        throw new XMLStreamException("Encountered unexpected event: " + event.getEventType());
                }
            }
        }
    }