/*
* 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 freemarker.ext.beans;
import freemarker.template.ObjectWrapper;
/**
* Marker interface useful when used together with {@link MethodAppearanceFineTuner} and such customizer objects, to
* indicate that it <b>doesn't contain reference to the {@link ObjectWrapper}</b> (so beware with non-static inner
* classes) and can be and should be used in call introspection cache keys. This also implies that you won't
* create many instances of the class, rather just reuse the same (or same few) instances over and over. Furthermore,
* the instances must be thread-safe. The typical pattern in which this instance should be used is like this:
*
* <pre>static class MyMethodAppearanceFineTuner implements MethodAppearanceFineTuner, SingletonCustomizer {
*
* // This is the singleton:
* static final MyMethodAppearanceFineTuner INSTANCE = new MyMethodAppearanceFineTuner();
*
* // Private, so it can't be constructed from outside this class.
* private MyMethodAppearanceFineTuner() { }
*
* @Override
* public void fineTuneMethodAppearance(...) {
* // Do something here, only using the parameters and maybe some other singletons.
* ...
* }
*
* }</pre>
*
* @since 2.3.21
*/
public interface SingletonCustomizer {
}