    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
    015package 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 */
    022public 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}