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Resilience4j is a lightweight, easy-to-use fault tolerance library designed for Java8 and functional programming

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/*
 * Copyright 2019 Mahmoud Romeh
 *
 * 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 io.github.resilience4j.circuitbreaker.configure;

import io.github.resilience4j.circuitbreaker.CircuitBreaker;
import io.github.resilience4j.reactor.circuitbreaker.operator.CircuitBreakerOperator;
import org.aspectj.lang.ProceedingJoinPoint;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

/**
 * the Reactor breaker logic support for the spring AOP Conditional on Reactor class existence on
 * spring class loader
 */
public class ReactorCircuitBreakerAspectExt implements CircuitBreakerAspectExt {

    private static final Logger logger = LoggerFactory
        .getLogger(ReactorCircuitBreakerAspectExt.class);

    /**
     * @param returnType the AOP method return type class
     * @return boolean if the method has Reactor return type
     */
    @Override
    public boolean canHandleReturnType(Class returnType) {
        return (Flux.class.isAssignableFrom(returnType)) || (Mono.class
            .isAssignableFrom(returnType));
    }

    /**
     * handle the Spring web flux (Flux /Mono) return types AOP based into reactor circuit-breaker
     * See {@link io.github.resilience4j.reactor.circuitbreaker.operator.CircuitBreakerOperator} for
     * details.
     *
     * @param proceedingJoinPoint Spring AOP proceedingJoinPoint
     * @param circuitBreaker      the configured circuitBreaker
     * @param methodName          the method name
     * @return the result object
     * @throws Throwable exception in case of faulty flow
     */
    @Override
    public Object handle(ProceedingJoinPoint proceedingJoinPoint, CircuitBreaker circuitBreaker,
        String methodName) throws Throwable {
        Object returnValue = proceedingJoinPoint.proceed();
        if (Flux.class.isAssignableFrom(returnValue.getClass())) {
            Flux fluxReturnValue = (Flux) returnValue;
            return fluxReturnValue.transformDeferred(
                io.github.resilience4j.reactor.circuitbreaker.operator.CircuitBreakerOperator
                    .of(circuitBreaker));
        } else if (Mono.class.isAssignableFrom(returnValue.getClass())) {
            Mono monoReturnValue = (Mono) returnValue;
            return monoReturnValue.transformDeferred(CircuitBreakerOperator.of(circuitBreaker));
        } else {
            logger.error("Unsupported type for Reactor circuit breaker {}",
                returnValue.getClass().getTypeName());
            throw new IllegalArgumentException(
                "Not Supported type for the circuit breaker in Reactor:" + returnValue.getClass()
                    .getName());

        }
    }
}