com.itextpdf.kernel.pdf.canvas.parser.listener.FilteredEventListener Maven / Gradle / Ivy

/*

    This file is part of the iText (R) project.
    Copyright (c) 1998-2018 iText Group NV
    Authors: Bruno Lowagie, Paulo Soares, et al.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License version 3
    as published by the Free Software Foundation with the addition of the
    following permission added to Section 15 as permitted in Section 7(a):
    FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
    ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
    OF THIRD PARTY RIGHTS

    This program is distributed in the hope that it will be useful, but
    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    or FITNESS FOR A PARTICULAR PURPOSE.
    See the GNU Affero General Public License for more details.
    You should have received a copy of the GNU Affero General Public License
    along with this program; if not, see http://www.gnu.org/licenses or write to
    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA, 02110-1301 USA, or download the license from the following URL:
    http://itextpdf.com/terms-of-use/

    The interactive user interfaces in modified source and object code versions
    of this program must display Appropriate Legal Notices, as required under
    Section 5 of the GNU Affero General Public License.

    In accordance with Section 7(b) of the GNU Affero General Public License,
    a covered work must retain the producer line in every PDF that is created
    or manipulated using iText.

    You can be released from the requirements of the license by purchasing
    a commercial license. Buying such a license is mandatory as soon as you
    develop commercial activities involving the iText software without
    disclosing the source code of your own applications.
    These activities include: offering paid services to customers as an ASP,
    serving PDFs on the fly in a web application, shipping iText with a closed
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    For more information, please contact iText Software Corp. at this
    address: [email protected]
 */
package com.itextpdf.kernel.pdf.canvas.parser.listener;

import com.itextpdf.kernel.pdf.canvas.parser.data.IEventData;
import com.itextpdf.kernel.pdf.canvas.parser.filter.IEventFilter;
import com.itextpdf.kernel.pdf.canvas.parser.EventType;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;

/**
 * An event listener which filters events on the fly before passing them on to the delegate.
 */
public class FilteredEventListener implements IEventListener {

    protected final List delegates;
    protected final List filters;

    /**
     * Constructs a {@link FilteredEventListener} empty instance.
     * Use {@link #attachEventListener(IEventListener, IEventFilter...)} to add an event listener along with its filters.
     */
    public FilteredEventListener() {
        this.delegates = new ArrayList<>();
        this.filters = new ArrayList<>();
    }

    /**
     * Constructs a {@link FilteredEventListener} instance with one delegate.
     * Use {@link #attachEventListener(IEventListener, IEventFilter...)} to add more {@link IEventListener} delegates
     * along with their filters.
     * @param delegate a delegate that fill be called when all the corresponding filters for an event pass
     * @param filterSet filters attached to the delegate that will be tested before passing an event on to the delegate
     */
    public FilteredEventListener(IEventListener delegate, IEventFilter... filterSet) {
        this();
        attachEventListener(delegate, filterSet);
    }

    /**
     * Attaches another {@link IEventListener} delegate with its filters.
     * When all the filters attached to the delegate for an event accept the event, the event will be passed on to
     * the delegate.
     * You can attach multiple delegates to this {@link FilteredEventListener} instance. The content stream will
     * be parsed just once, so it is better for performance than creating multiple {@link FilteredEventListener}
     * instances and parsing the content stream multiple times. This is useful, for instance, when you want
     * to extract content from multiple regions of a page.
     * @param delegate a delegate that fill be called when all the corresponding filters for an event pass
     * @param filterSet filters attached to the delegate that will be tested before passing an event on to the delegate
     * @return delegate that has been passed to the method, used for convenient call chaining
     */
    public  T attachEventListener(T delegate, IEventFilter... filterSet) {
        delegates.add(delegate);
        filters.add(filterSet);

        return delegate;
    }

    @Override
    public void eventOccurred(IEventData data, EventType type) {
        for (int i = 0; i < delegates.size(); i++) {
            IEventListener delegate = delegates.get(i);
            boolean filtersPassed = delegate.getSupportedEvents() == null || delegate.getSupportedEvents().contains(type);
            for (IEventFilter filter : filters.get(i)) {
                if (!filter.accept(data, type)) {
                    filtersPassed = false;
                    break;
                }
            }
            if (filtersPassed) {
                delegate.eventOccurred(data, type);
            }
        }
    }

    @Override
    public Set getSupportedEvents() {
        return null;
    }
}