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}