    001    // Copyright 2011 The Apache Software Foundation
    002    //
    003    // Licensed under the Apache License, Version 2.0 (the "License");
    004    // you may not use this file except in compliance with the License.
    005    // You may obtain a copy of the License at
    006    //
    007    // http://www.apache.org/licenses/LICENSE-2.0
    008    //
    009    // Unless required by applicable law or agreed to in writing, software
    010    // distributed under the License is distributed on an "AS IS" BASIS,
    011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012    // See the License for the specific language governing permissions and
    013    // limitations under the License.
    014
    015    package org.apache.tapestry5.internal.plastic;
    016
    017    /**
    018     * An object that can be locked, at which point most of its functionality is disabled. This conforms to general
    019     * builder approach used throughout Plastic where objects have an active construction phase, but are then locked
    020     * (to encourage user code to discard them after they are no longer of any use).
    021     */
    022    public class Lockable
    023    {
    024        private boolean locked;
    025
    026        /**
    027         * Checks to see if the object has been locked.
    028         *
    029         * @throws IllegalStateException if {@link #lock()} has been invoked.
    030         */
    031        protected void check()
    032        {
    033            if (locked)
    034                throw new IllegalStateException(toString() + " has been locked and can no longer be used.");
    035        }
    036
    037        /**
    038         * Invokes {@link #check()}, then sets the locked flag. Subsequent calls to {@link #check()} will fail.
    039         */
    040        protected void lock()
    041        {
    042            check();
    043
    044            locked = true;
    045        }
    046    }