68 lines
1.9 KiB
Java
68 lines
1.9 KiB
Java
package dev.kske.eventbus.core;
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import static java.lang.annotation.ElementType.METHOD;
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import static java.lang.annotation.RetentionPolicy.RUNTIME;
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import java.lang.annotation.*;
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/**
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* Indicates that a method is an event handler. To be successfully used as such, the method has to
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* comply with the following specifications:
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* <ul>
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* <li>Declared inside a class that implements {@link EventListener}</li>
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* <li>Specifying an event type by either
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* <ul>
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* <li>Declaring one parameter of a type that implements {@link IEvent}</li>
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* <li>Defining the class of the event using the {@link Event#eventType()} value</li>
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* </ul>
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* </li>
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* <li>Return type of {@code void}</li>
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* </ul>
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*
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* @author Kai S. K. Engelbart
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* @since 0.0.1
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*/
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@Documented
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@Retention(RUNTIME)
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@Target(METHOD)
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public @interface Event {
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/**
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* Defines the priority of the event handler. Handlers are executed in descending order of their
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* priority.
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* <p>
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* The execution order of handlers with the same priority is undefined.
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*
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* @return the priority of the event handler
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* @since 0.0.1
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*/
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int priority() default 100;
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/**
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* Defines whether instances of subtypes of the event type are dispatched to the event handler.
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*
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* @return whether the event handler includes subtypes
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* @since 0.0.4
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*/
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boolean includeSubtypes() default false;
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/**
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* Defines the event type the handler listens to. If this value is set, the handler is not
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* allowed to declare parameters.
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* <p>
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* This is useful when the event handler does not utilize the event instance.
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*
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* @return the event type accepted by the handler
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* @since 0.0.3
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*/
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Class<? extends IEvent> eventType() default USE_PARAMETER.class;
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/**
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* Signifies that the event type the handler listens to is determined by the type of its only
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* parameter.
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*
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* @since 0.0.3
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*/
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static final class USE_PARAMETER implements IEvent {}
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}
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