/**
* Copyright 2015 Netflix, 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.
*/
package com.netflix.hystrix.strategy.concurrency;
/**
* Implementation of {@link HystrixRequestVariable} which forwards to the wrapped
* {@link HystrixRequestVariableLifecycle}.
* <p>
* This implementation also returns null when {@link #get()} is called while the {@link HystrixRequestContext} has not
* been initialized rather than throwing an exception, allowing for use in a {@link HystrixConcurrencyStrategy} which
* does not depend on an a HystrixRequestContext
*/
public class HystrixLifecycleForwardingRequestVariable<T> extends HystrixRequestVariableDefault<T> {
private final HystrixRequestVariableLifecycle<T> lifecycle;
/**
* Creates a HystrixRequestVariable which will return data as provided by the {@link HystrixRequestVariableLifecycle}
* @param lifecycle lifecycle used to provide values. Must have the same type parameter as the constructed instance.
*/
public HystrixLifecycleForwardingRequestVariable(HystrixRequestVariableLifecycle<T> lifecycle) {
this.lifecycle = lifecycle;
}
/**
* Delegates to the wrapped {@link HystrixRequestVariableLifecycle}
* @return T with initial value or null if none.
*/
@Override
public T initialValue() {
return lifecycle.initialValue();
}
/**
* Delegates to the wrapped {@link HystrixRequestVariableLifecycle}
* @param value
* of request variable to allow cleanup activity.
* <p>
* If nothing needs to be cleaned up then nothing needs to be done in this method.
*/
@Override
public void shutdown(T value) {
lifecycle.shutdown(value);
}
/**
* Return null if the {@link HystrixRequestContext} has not been initialized for the current thread.
* <p>
* If {@link HystrixRequestContext} has been initialized then call method in superclass:
* {@link HystrixRequestVariableDefault#get()}
*/
@Override
public T get() {
if (!HystrixRequestContext.isCurrentThreadInitialized()) {
return null;
}
return super.get();
}
}