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Zodiac Feign Core

There is a newer version: 1.6.8

/**
 * Copyright 2012-2020 The Feign Authors
 *
 * 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 feign.hystrix;

import java.util.Objects;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Used to control the fallback given its cause.
 *
 * Ex.
 * 
 *  * {@code
 * // This instance will be invoked if there are errors of any kind.
 * FallbackFactory fallbackFactory = cause -> (owner, repo) -> {
 *   if (cause instanceof FeignException && ((FeignException) cause).status() == 403) {
 *     return Collections.emptyList();
 *   } else {
 *     return Arrays.asList("yogi");
 *   }
 * };
 *
 * GitHub github = HystrixFeign.builder().target(GitHub.class, "https://api.github.com", fallbackFactory);
 * }
 * 
 *
 * @param the feign interface type
 */
public interface FallbackFactory {

    T create(Throwable cause);

    /** Returns a constant fallback after logging the cause to FINE level. */
    final class Default implements FallbackFactory {
        // jul to not add a dependency
        final Logger logger;
        final T constant;

        public Default(T constant) {
            this(constant, Logger.getLogger(Default.class.getName()));
        }

        Default(T constant, Logger logger) {
            this.constant = Objects.requireNonNull(constant, "fallback");
            this.logger = Objects.requireNonNull(logger, "logger");
        }

        @Override
        public T create(Throwable cause) {
            if (logger.isLoggable(Level.FINE)) {
                logger.log(Level.FINE, "fallback due to: " + cause.getMessage(), cause);
            }
            return constant;
        }

        @Override
        public String toString() {
            return constant.toString();
        }
    }

}