core/api/src/main/java/org/apache/polygene/api/concern/ConcernOf.java

/*
 *  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
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 *
 *
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package org.apache.polygene.api.concern;

import org.apache.polygene.api.concern.internal.ConcernFor;

/**
 * Base class for Concerns. It introduces a typed "next" pointer
 * that Concerns can use to invoke the next Concern (or mixin) in
 * the chain.
 * <p>
 * Generic Concerns should subclass {@link GenericConcern} instead.
 * </p>
 * <p>
 * Concerns implementations must be thread-safe in their implementation,
 * as multiple threads may share instances.
 * </p>
 */
public abstract class ConcernOf<T>
{
    /**
     * The "next" pointer. This points to
     * the next concern in the chain or the mixin
     * to be invoked.
     */
    final
    @ConcernFor
    protected T next = null;
}