event-bus/event-bus-core/src/main/java/dev/kske/eventbus/core/Event.java

50 lines
1.2 KiB
Java

package dev.kske.eventbus.core;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.*;
/**
* Indicates that a method is an event handler. To be successfully used as such, the method has to
* comply with the following specifications:
* <ul>
* <li>Specifying an event type by either
* <ul>
* <li>Declaring one object parameter</li>
* <li>Defining the class of the event using the annotation value</li>
* </ul>
* </li>
* <li>Return type of {@code void}</li>
* </ul>
*
* @author Kai S. K. Engelbart
* @since 0.0.1
* @see Polymorphic
* @see Priority
*/
@Documented
@Retention(RUNTIME)
@Target(METHOD)
public @interface Event {
/**
* Defines the event type the handler listens to. If this value is set, the handler is not
* allowed to declare parameters.
* <p>
* This is useful when the event handler does not utilize the event instance.
*
* @return the event type accepted by the handler
* @since 1.0.0
*/
Class<?> value() default USE_PARAMETER.class;
/**
* Signifies that the event type the handler listens to is determined by the type of its only
* parameter.
*
* @since 0.0.3
*/
static final class USE_PARAMETER {}
}