PostWorkComparator.java

/*
 * #%L
 * FlatPack serialization code
 * %%
 * Copyright (C) 2012 Perka Inc.
 * %%
 * Licensed 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.
 * #L%
 */
package com.getperka.flatpack.ext;

import static com.getperka.flatpack.util.FlatPackCollections.mapForLookup;

import java.util.Comparator;
import java.util.Map;
import java.util.concurrent.Callable;

/**
 * Used to sort the callables passed into
 * {@link DeserializationContext#addPostWork(java.util.concurrent.Callable)}.
 */
class PostWorkComparator implements Comparator<Callable<?>> {
  private static Map<Class<?>, Integer> order = mapForLookup();

  /**
   * Avoid the overhead of repeated reflection.
   */
  private static synchronized int getOrder(Class<?> clazz) {
    Integer toReturn = order.get(clazz);
    if (toReturn != null) {
      return toReturn;
    }
    PostWorkOrder annotation = clazz.getAnnotation(PostWorkOrder.class);
    int value = annotation == null ? 0 : annotation.value();
    order.put(clazz, value);
    return value;
  }

  @Override
  public int compare(Callable<?> o1, Callable<?> o2) {
    return getOrder(o1.getClass()) - getOrder(o2.getClass());
  }

}