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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;
 
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.

public @interface Pass {

    
The asynchronous passing mode.

Returns:
the mode.
    PassingMode mode() default .;

    
The bound class.

Returns:
the class.
    Class<?> value();

    
Asynchronous passing mode.
The type indicates in which way a parameter is passed to the wrapped method or the result is passed outside.
    enum PassingMode {

        
Object mode.
The variable is just read from or passed to an output channel.

The annotated parameter must extends an 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 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 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 java.util.List.

        PARALLEL,
        
Automatic mode.
The mode is automatically assigned based on the parameter or return type. Namely: if the parameters match the COLLECTION async 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 async 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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