global.namespace.neuron.di.java.Neuron Maven / Gradle / Ivy

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/*
 * Copyright © 2016 - 2019 Schlichtherle IT Services
 *
 * 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
 *
 *     https://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 global.namespace.neuron.di.java;

import java.lang.annotation.*;

/**
 * Indicates that the annotated class or interface is a neuron type.
 * A neuron type is supposed to have synapse methods to make contact with its dependencies.
 * All abstract, parameterless methods in a neuron type are synapse methods - there is no need to declare them.
 * The {@link Incubator} implements these methods when breeding a neuron so that its dependencies are resolved
 * lazily, that is, no sooner as the neuron calls a synapse method.
 * In a nutshell, a neuron resolves all its dependencies lazily by calling its synapse methods, so they all have a name
 * and a type.
 * 
 * If this annotation is present on a class, it gets inherited by any subclass.
 * In compliance with the Java Language Specification, this does not apply to interfaces.
 * 

 * This annotation can also be applied to custom annotation types, in which case any class or interface annotated with
 * these is treated as if it's directly annotated with this annotation.
 * For example, the following annotation caches all synapse values using a thread-safe strategy:
 * 
{@code
 *     import global.namespace.neuron.di.java.*;
 *     import java.lang.annotation.*;
 *
 *     @Neuron(cachingStrategy = CachingStrategy.THREAD_SAFE)
 *     @Inherited
 *     @Documented
 *     @Retention(RetentionPolicy.RUNTIME)
 *     @Target(ElementType.TYPE)
 *     public @interface ThreadSafeCachingNeuron {
 *     }
 * }
 *
 * @see Neuron on the English Wikipedia
 */
@Inherited
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface Neuron {

    /**
     * Configures the strategy for caching the return value of synapse methods which are not annotated with
     * {@link Caching}.
     */
    CachingStrategy cachingStrategy() default CachingStrategy.DISABLED;
}