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.
/**
 * 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 HystrixRequestVariable which forwards to the wrapped HystrixRequestVariableLifecycle. 
 This implementation also returns null when get() is called while the HystrixRequestContext has not been initialized rather than throwing an exception, allowing for use in a HystrixConcurrencyStrategy which does not depend on an a HystrixRequestContext /**
 * 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 HystrixRequestVariableLifecycle 
Params:
lifecycle – lifecycle used to provide values. Must have the same type parameter as the constructed instance./**
     * 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 HystrixRequestVariableLifecycle 
Returns:
T with initial value or null if none./**
     * 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 HystrixRequestVariableLifecycle 
Params:
value – 
           of request variable to allow cleanup activity.
           

           If nothing needs to be cleaned up then nothing needs to be done in this method./**
     * 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 HystrixRequestContext has not been initialized for the current thread. 
 If HystrixRequestContext has been initialized then call method in superclass: HystrixRequestVariableDefault.get() /**
     * 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();
    }

}