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/*
 * 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.gh.bmd.jrt.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * This annotation is used to decorate methods that are to be invoked in an asynchronous way.
* Note that the piece of code inside such methods will be automatically protected so to avoid * concurrency issues. Though, other parts of the code inside the same class will be not.
* In order to prevent unexpected behaviors, it is advisable to avoid using the same class fields * (unless immutable) in protected and non-protected code, or to call synchronous methods through * the framework as well. *

* The only use case in which this annotation is useful, is when an interface is used as a mirror * of another class methods. The interface can take some input parameters or return an output in an * asynchronous way. In such cases, the value specified in the annotation will indicate the type of * the parameter or the return type expected by the target method. *

* For example, a method taking two integers: *

*

 *     
 *
 *         public int sum(int i1, int i2);
 *     
 * 
* can be mirrored by a method defined as: *

*

 *     
 *
 *         public int sum(@Pass(int.class) OutputChannel<Integer> i1, int i2);
 *     
 * 
*

* Additionally, the interface can return the result as an output channel whose output data will be * passed only when available. *

* For example, a method returning an integer: *

*

 *     
 *
 *         public int sum(int i1, int i2);
 *     
 * 
* can be mirrored by a method defined as: *

*

 *     
 *
 *         @Pass(int.class)
 *         public OutputChannel<Integer> sum(int i1, int i2);
 *     
 * 
*

* The interface can also return an array or list of outputs: *

*

 *     
 *
 *         @Pass(int.class)
 *         public List<Integer> sum(int i1, int i2);
 *     
 * 
*

* Note that the type of asynchronicity is automatically inferred by the mirror and the target type, * unless specifically chosen through the annotation mode attribute. *

* Remember also that, in order for the annotation to properly work at run time, you will need to * add the following rules to your Proguard file (if employing it for shrinking or obfuscation): *

 *     
 *
 *         -keepattributes RuntimeVisibleAnnotations
 *
 *         -keepclassmembers class ** {
 *              @com.gh.bmd.jrt.annotation.Pass *;
 *         }
 *     
 * 
*

* Created by davide on 1/31/15. */ @Inherited @Target({ElementType.PARAMETER, ElementType.METHOD}) @Retention(RetentionPolicy.RUNTIME) public @interface Pass { /** * The asynchronous passing mode. * * @return the mode. */ PassMode mode() default PassMode.AUTO; /** * The bound class. * * @return the class. */ Class value(); /** * Asynchronous pass mode.
* The type indicates in which way a parameter is passed to the wrapped method or the result * is passed outside. */ enum PassMode { /** * Object mode.
* The variable is just read from or passed to an output channel. *

* The annotated parameter must extends an {@link com.gh.bmd.jrt.channel.OutputChannel}, * while an annotated method must return a superclass of it. */ OBJECT, /** * Collection mode.
* The inputs are collected from the channel and passed as an array or collection to the * wrapped method. In a dual way, the element of the result array or collection are passed * one by one to the output channel. *

* The annotated parameter must extends an {@link com.gh.bmd.jrt.channel.OutputChannel} and * must be the only parameter accepted by the method, while an annotated method must return * a superclass of it. */ COLLECTION, /** * Parallel mode.
* Each input is passed to a different parallel invocation of the wrapped method. *

* The annotated parameter must be an array or implement an {@link java.lang.Iterable} and * must be the only parameter accepted by the method, while an annotated method must return * an array or a superclass of a {@link java.util.List}. */ PARALLEL, /** * Automatic mode.
* The mode is automatically assigned based to the parameter or return type. Namely: if the * parameters match the COLLECTION pass mode, they are assigned it; if they match the OBJECT * mode, they are assigned the latter; finally the PARALLEL conditions are checked. *

* Dually, if the return type matches the PARALLEL pass mode, it is assigned it; if it * matches the COLLECTION mode, it is assigned the latter; finally the OBJECT conditions are * checked. */ AUTO } }





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