core/src/main/java/org/jclouds/functions/ExceptionToValueOrPropagate.java

/**
 *
 * Copyright (C) 2009 Cloud Conscious, LLC. <info@cloudconscious.com>
 *
 * ====================================================================
 * 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.
 * ====================================================================
 */
package org.jclouds.functions;

import static org.jclouds.util.Utils.propagateOrNull;

import java.util.List;

import javax.annotation.Nullable;

import com.google.common.base.Function;
import com.google.common.base.Throwables;
import com.google.common.collect.Iterables;

/**
 * 
 * @author Adrian Cole
 */
public class ExceptionToValueOrPropagate<E extends Exception, T> implements Function<Exception, T> {

   private final Class<E> matchingClass;
   private final T value;

   public ExceptionToValueOrPropagate(Class<E> matchingClass, @Nullable T value) {
      this.matchingClass = matchingClass;
      this.value = value;
   }

   @SuppressWarnings("unchecked")
   @Override
   public T apply(Exception from) {
      List<Throwable> throwables = Throwables.getCausalChain(from);
      Iterable<E> matchingThrowables = Iterables.filter(throwables, matchingClass);
      if (Iterables.size(matchingThrowables) >= 1)
         return value;
      return (T) propagateOrNull(from);
   }

}