# FileCleanerCleanup.java

    /*
     * 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
     *
     *      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.commons.fileupload.servlet;

    import javax.servlet.ServletContext;
    import javax.servlet.ServletContextEvent;
    import javax.servlet.ServletContextListener;

    import org.apache.commons.io.FileCleaningTracker;

    /**
     * A servlet context listener, which ensures that the
     * {@link FileCleaningTracker}'s reaper thread is terminated,
     * when the web application is destroyed.
     */
    public class FileCleanerCleanup implements ServletContextListener {

        /**
         * Attribute name, which is used for storing an instance of
         * {@link FileCleaningTracker} in the web application.
         */
        public static final String FILE_CLEANING_TRACKER_ATTRIBUTE
            = FileCleanerCleanup.class.getName() + ".FileCleaningTracker";

        /**
         * Returns the instance of {@link FileCleaningTracker}, which is
         * associated with the given {@link ServletContext}.
         *
         * @param servletContext The servlet context to query
         * @return The contexts tracker
         */
        public static FileCleaningTracker getFileCleaningTracker(final ServletContext servletContext) {
            return (FileCleaningTracker) servletContext.getAttribute(FILE_CLEANING_TRACKER_ATTRIBUTE);
        }

        /**
         * Sets the instance of {@link FileCleaningTracker}, which is
         * associated with the given {@link ServletContext}.
         *
         * @param servletContext The servlet context to modify
         * @param tracker The tracker to set
         */
        public static void setFileCleaningTracker(final ServletContext servletContext, final FileCleaningTracker tracker) {
            servletContext.setAttribute(FILE_CLEANING_TRACKER_ATTRIBUTE, tracker);
        }

        /**
         * Constructs a new instance.
         */
        public FileCleanerCleanup() {
            // empty
        }

        /**
         * Called when the web application is being destroyed.
         * Calls {@link FileCleaningTracker#exitWhenFinished()}.
         *
         * @param sce The servlet context, used for calling
         *     {@link #getFileCleaningTracker(ServletContext)}.
         */
        @Override
        public void contextDestroyed(final ServletContextEvent sce) {
            getFileCleaningTracker(sce.getServletContext()).exitWhenFinished();
        }

        /**
         * Called when the web application is initialized. Does
         * nothing.
         *
         * @param sce The servlet context, used for calling
         *   {@link #setFileCleaningTracker(ServletContext, FileCleaningTracker)}.
         */
        @Override
        public void contextInitialized(final ServletContextEvent sce) {
            setFileCleaningTracker(sce.getServletContext(),
                    new FileCleaningTracker());
        }

    }