ExtensibleFilter.java

/**
 * Copyright (C) 2009 eXo Platform SAS.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.exoplatform.web.filter;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;


/**
 * This class allows the rest of the platform to define new filters thanks to the external plugins.
 *
 * Created by The eXo Platform SAS Author : Nicolas Filotto nicolas.filotto@exoplatform.com 25 sept. 2009
 */
public class ExtensibleFilter {

    /**
     * List of all the sub filters
     */
    private volatile List<FilterDefinition> filters = Collections.unmodifiableList(new ArrayList<FilterDefinition>());

    /**
     * Adds new {@link FilterDefinition}
     */
    public void addFilterDefinitions(FilterDefinitionPlugin plugin) {
        addFilterDefinitions(plugin.getFilterDefinitions());
    }

    /**
     * Adds new {@link FilterDefinition}
     */
    void addFilterDefinitions(List<FilterDefinition> pluginFilters) {
        if (pluginFilters == null || pluginFilters.isEmpty()) {
            // No filter to add
            return;
        }
        synchronized (this) {
            List<FilterDefinition> result = new ArrayList<FilterDefinition>(filters);
            result.addAll(pluginFilters);
            this.filters = Collections.unmodifiableList(result);
        }
    }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain, String path) throws IOException,
            ServletException {
        ExtensibleFilterChain efChain = new ExtensibleFilterChain(chain, filters, path);
        efChain.doFilter(request, response);
    }

    private static class ExtensibleFilterChain implements FilterChain {

        private final FilterChain parentChain;

        private final Iterator<FilterDefinition> filters;

        private final String path;

        private ExtensibleFilterChain(FilterChain parentChain, List<FilterDefinition> filters, String path_) {
            this.parentChain = parentChain;
            this.filters = filters.iterator();
            this.path = path_;
        }

        public void doFilter(ServletRequest request, ServletResponse response) throws IOException, ServletException {
            while (filters.hasNext()) {
                FilterDefinition filterDef = filters.next();
                if (filterDef.getMapping().match(path)) {
                    filterDef.getFilter().doFilter(request, response, this);
                    return;
                }
            }
            parentChain.doFilter(request, response);
        }
    }
}