详解Guava中EventBus的使用

关于Guava中EventBus的使用，以下是详细攻略：

概述

Guava是一套基于Java语言的、用于简化开发的开源工具包，其中的EventBus是一种轻量级的事件发布（Publish-Subscribe）模式的实现。在应用程序内部，发布者（Producer）不必和特定的消费者（Consumer）直接通信，而是将消息（Event）发送到一个EventBus上，EventBus会根据主题（Topic）将该消息投递给订阅该主题的所有消费者，从而实现了松耦合的事件处理机制。

使用

以下是EventBus的使用步骤：

引入依赖

• Maven

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>30.0-jre</version>
</dependency>

定义事件类

事件类是一个普通的Java类，通常包含事件相关信息的成员变量和相关的方法。

public class CustomEvent {
    private String message;

    public CustomEvent(String message) {
        this.message = message;
    }

    public String getMessage() {
        return message;
    }
}

定义订阅者

一个订阅者将会处理一个或多个事件。订阅者需要包含一个或多个使用@Subscribe注解的事件处理方法。

public class CustomSubscriber {
    @Subscribe
    public void handleCustomEvent(CustomEvent event) {
        System.out.println("Received custom event with message: " + event.getMessage());
    }
}

创建EventBus对象

EventBus eventBus = new EventBus();

注册订阅者

CustomSubscriber subscriber = new CustomSubscriber();
eventBus.register(subscriber);

发布事件

eventBus.post(new CustomEvent("Hello world!"));

此时会输出 Received custom event with message: Hello world!

示例

以下是两个示例：

示例1：基本用法

public class Main {
    static class CustomEvent {
        private String message;

        public CustomEvent(String message) {
            this.message = message;
        }

        public String getMessage() {
            return message;
        }
    }

    static class CustomSubscriber {
        @Subscribe
        public void handleCustomEvent(CustomEvent event) {
            System.out.println("Received custom event with message: " + event.getMessage());
        }
    }

    public static void main(String[] args) {
        EventBus eventBus = new EventBus();
        CustomSubscriber subscriber = new CustomSubscriber();
        eventBus.register(subscriber);
        eventBus.post(new CustomEvent("Hello world!"));
    }
}

输出：

Received custom event with message: Hello world!

示例2：多个订阅者处理同一事件

public class Main {
    static class CustomEvent {
        private String message;

        public CustomEvent(String message) {
            this.message = message;
        }

        public String getMessage() {
            return message;
        }
    }

    static class FirstSubscriber {
        @Subscribe
        public void handleCustomEvent(CustomEvent event) {
            System.out.println("First subscriber received custom event with message: " + event.getMessage());
        }
    }

    static class SecondSubscriber {
        @Subscribe
        public void handleCustomEvent(CustomEvent event) {
            System.out.println("Second subscriber received custom event with message: " + event.getMessage());
        }
    }

    public static void main(String[] args) {
        EventBus eventBus = new EventBus();
        FirstSubscriber firstSubscriber = new FirstSubscriber();
        SecondSubscriber secondSubscriber = new SecondSubscriber();
        eventBus.register(firstSubscriber);
        eventBus.register(secondSubscriber);
        eventBus.post(new CustomEvent("Hello world!"));
    }
}

输出：

First subscriber received custom event with message: Hello world!
Second subscriber received custom event with message: Hello world!

以上就是关于Guava中EventBus的使用的详细攻略了。