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    }