[Feature Request] 新增观察者事件功能

unknowIfGuestInDream commented 1 year ago

Checklist

[X] I searched exising issues and no one else requests similar feature.
[X] I think that 25%+ users are positive towards this feature.

Describe the feature

计划新增 EventListener 注解，可以参照hutool是否有相应封装

Additional context

https://blog.csdn.net/qq_28051649/article/details/62216648

unknowIfGuestInDream commented 1 year ago

参考SpringBoot event的实现

unknowIfGuestInDream commented 1 year ago

考虑调用者通过线程池来执行

unknowIfGuestInDream commented 1 year ago

考虑给InterfaceScanner 中加缓存来优化启动时初始化性能

unknowIfGuestInDream commented 1 year ago

参考: https://www.hangge.com/blog/cache/detail_3259.html https://github.com/unknowIfGuestInDream/DesignpatternTest/blob/master/src/%E8%A7%82%E5%AF%9F%E8%80%85%E6%A8%A1%E5%BC%8F/%E5%9F%BA%E4%BA%8EJavaAPI%E5%AE%9E%E7%8E%B0%E9%80%9A%E7%9F%A5%E6%9C%BA%E5%88%B6/Test.java

Java - 使用Observer实现观察者模式、EventListener实现监听器模式详解
JDK 不仅提供了 Observable 类、Observer 接口用来支持观察者模式，而且也提供了 EventObject、EventListener 接口来支持事件监听模式。虽然两者属于同一类型模式，都属于回调机制、主动推送消息，但使用场景有些区别，或者说监听器模式是观察者模式在特定场景下的一种改造和应用......

GitHub
DesignpatternTest/Test.java at master · unknowIfGuestInDream/DesignpatternTest
设计模式练习. Contribute to unknowIfGuestInDream/DesignpatternTest development by creating an account on GitHub.

unknowIfGuestInDream commented 1 year ago

/**
 * Class to be extended by all application events. Abstract as it
 * doesn't make sense for generic events to be published directly.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see org.springframework.context.ApplicationListener
 * @see org.springframework.context.event.EventListener
 */
public abstract class ApplicationEvent extends EventObject {

    /** use serialVersionUID from Spring 1.2 for interoperability. */
    private static final long serialVersionUID = 7099057708183571937L;

    /** System time when the event happened. */
    private final long timestamp;

    /**
     * Create a new {@code ApplicationEvent} with its {@link #getTimestamp() timestamp}
     * set to {@link System#currentTimeMillis()}.
     * @param source the object on which the event initially occurred or with
     * which the event is associated (never {@code null})
     * @see #ApplicationEvent(Object, Clock)
     */
    public ApplicationEvent(Object source) {
        super(source);
        this.timestamp = System.currentTimeMillis();
    }

    /**
     * Create a new {@code ApplicationEvent} with its {@link #getTimestamp() timestamp}
     * set to the value returned by {@link Clock#millis()} in the provided {@link Clock}.
     * <p>This constructor is typically used in testing scenarios.
     * @param source the object on which the event initially occurred or with
     * which the event is associated (never {@code null})
     * @param clock a clock which will provide the timestamp
     * @since 5.3.8
     * @see #ApplicationEvent(Object)
     */
    public ApplicationEvent(Object source, Clock clock) {
        super(source);
        this.timestamp = clock.millis();
    }

    /**
     * Return the time in milliseconds when the event occurred.
     * @see #ApplicationEvent(Object)
     * @see #ApplicationEvent(Object, Clock)
     */
    public final long getTimestamp() {
        return this.timestamp;
    }

}

unknowIfGuestInDream commented 1 year ago

/**
 * Annotation that marks a method as a listener for application events.
 *
 * <p>If an annotated method supports a single event type, the method may
 * declare a single parameter that reflects the event type to listen to.
 * If an annotated method supports multiple event types, this annotation
 * may refer to one or more supported event types using the {@code classes}
 * attribute. See the {@link #classes} javadoc for further details.
 *
 * <p>Events can be {@link ApplicationEvent} instances as well as arbitrary
 * objects.
 *
 * <p>Processing of {@code @EventListener} annotations is performed via
 * the internal {@link EventListenerMethodProcessor} bean which gets
 * registered automatically when using Java config or manually via the
 * {@code <context:annotation-config/>} or {@code <context:component-scan/>}
 * element when using XML config.
 *
 * <p>Annotated methods may have a non-{@code void} return type. When they
 * do, the result of the method invocation is sent as a new event. If the
 * return type is either an array or a collection, each element is sent
 * as a new individual event.
 *
 * <p>This annotation may be used as a <em>meta-annotation</em> to create custom
 * <em>composed annotations</em>.
 *
 * <h3>Exception Handling</h3>
 * <p>While it is possible for an event listener to declare that it
 * throws arbitrary exception types, any checked exceptions thrown
 * from an event listener will be wrapped in an
 * {@link java.lang.reflect.UndeclaredThrowableException UndeclaredThrowableException}
 * since the event publisher can only handle runtime exceptions.
 *
 * <h3>Asynchronous Listeners</h3>
 * <p>If you want a particular listener to process events asynchronously, you
 * can use Spring's {@link org.springframework.scheduling.annotation.Async @Async}
 * support, but be aware of the following limitations when using asynchronous events.
 *
 * <ul>
 * <li>If an asynchronous event listener throws an exception, it is not propagated
 * to the caller. See {@link org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler
 * AsyncUncaughtExceptionHandler} for more details.</li>
 * <li>Asynchronous event listener methods cannot publish a subsequent event by returning a
 * value. If you need to publish another event as the result of the processing, inject an
 * {@link org.springframework.context.ApplicationEventPublisher ApplicationEventPublisher}
 * to publish the event manually.</li>
 * </ul>
 *
 * <h3>Ordering Listeners</h3>
 * <p>It is also possible to define the order in which listeners for a
 * certain event are to be invoked. To do so, add Spring's common
 * {@link org.springframework.core.annotation.Order @Order} annotation
 * alongside this event listener annotation.
 *
 * @author Stephane Nicoll
 * @author Sam Brannen
 * @since 4.2
 * @see EventListenerMethodProcessor
 * @see org.springframework.transaction.event.TransactionalEventListener
 */
@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface EventListener {

    /**
     * Alias for {@link #classes}.
     */
    @AliasFor("classes")
    Class<?>[] value() default {};

    /**
     * The event classes that this listener handles.
     * <p>If this attribute is specified with a single value, the
     * annotated method may optionally accept a single parameter.
     * However, if this attribute is specified with multiple values,
     * the annotated method must <em>not</em> declare any parameters.
     */
    @AliasFor("value")
    Class<?>[] classes() default {};

    /**
     * Spring Expression Language (SpEL) expression used for making the event
     * handling conditional.
     * <p>The event will be handled if the expression evaluates to boolean
     * {@code true} or one of the following strings: {@code "true"}, {@code "on"},
     * {@code "yes"}, or {@code "1"}.
     * <p>The default expression is {@code ""}, meaning the event is always handled.
     * <p>The SpEL expression will be evaluated against a dedicated context that
     * provides the following metadata:
     * <ul>
     * <li>{@code #root.event} or {@code event} for references to the
     * {@link ApplicationEvent}</li>
     * <li>{@code #root.args} or {@code args} for references to the method
     * arguments array</li>
     * <li>Method arguments can be accessed by index. For example, the first
     * argument can be accessed via {@code #root.args[0]}, {@code args[0]},
     * {@code #a0}, or {@code #p0}.</li>
     * <li>Method arguments can be accessed by name (with a preceding hash tag)
     * if parameter names are available in the compiled byte code.</li>
     * </ul>
     */
    String condition() default "";

    /**
     * An optional identifier for the listener, defaulting to the fully-qualified
     * signature of the declaring method (e.g. "mypackage.MyClass.myMethod()").
     * @since 5.3.5
     * @see SmartApplicationListener#getListenerId()
     * @see ApplicationEventMulticaster#removeApplicationListeners(Predicate)
     */
    String id() default "";

}

unknowIfGuestInDream commented 1 year ago

https://github.com/spring-projects/spring-framework

GitHub
GitHub - spring-projects/spring-framework: Spring Framework
Spring Framework. Contribute to spring-projects/spring-framework development by creating an account on GitHub.

unknowIfGuestInDream commented 1 year ago

https://github.com/KAMO030/kamo-core

GitHub
GitHub - KAMO030/kamo-core: 基于原生jdk实现的一些小工具，可用来练习编程思维
基于原生jdk实现的一些小工具，可用来练习编程思维. Contribute to KAMO030/kamo-core development by creating an account on GitHub.