OSGi 系列（十四）之 Event Admin Service OSGi 系列（十四）之 Event Admin Service

OSGi 的 Event Admin 服务规范提供了开发者基于发布/订阅模型，通过事件机制实现 Bundle 间协作的标准通讯方式。

事件发布者使用 Event Admin 服务发送基于主题 (Topic) 的事件，任何对某一主题感兴趣的事件订阅者都会收到该事件，并且做出相应的反应。

1. Event Admin Service 介绍

(1) Event Admin Service 规范

compendium 规范提供了 Event Admin Service 服务，具体规范见 org.osgi.service.event

OSGi 系列（十四）之 Event Admin Service
OSGi 系列（十四）之 Event Admin Service

(2) Topic 的规范

/不能用于开头或者结尾
可以使用 A-Z,a-z,0-9,-,_

2. 快速入门

2.1 环境准备

<dependency>
    <groupId>org.osgi</groupId>
    <artifactId>org.osgi.core</artifactId>
    <version>5.0.0</version>
</dependency>
<dependency>
    <groupId>org.osgi</groupId>
    <artifactId>org.osgi.compendium</artifactId>
    <version>5.0.0</version>
</dependency>

2.2 新建 2 个 bundle，一个发布事件(osgi-event-publish)，一个接收事件(osgi-event-subscribe)

2.3 发布事件(osgi-event-publish)

import java.util.HashMap;
import java.util.Map;

import org.osgi.service.event.Event;
import org.osgi.service.event.EventAdmin;

public class EventPublish {

    private EventAdmin eventAdmin;
    
    public void publish() {
        Map<String, String> content = new HashMap<>();
        content.put("phone", "10086");
        content.put("content", "ye");
        eventAdmin.postEvent(new Event("send/10086", content));
    }

    public void setEventAdmin(EventAdmin eventAdmin) {
        this.eventAdmin = eventAdmin;
    }
}

blueprint.xml 配制

<?xml version="1.0" encoding="UTF-8"?>
<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://www.osgi.org/xmlns/blueprint/v1.0.0 http://www.osgi.org/xmlns/blueprint/v1.0.0/blueprint.xsd">
    
    <reference  />

    <bean class="com.edu.osgi.event.publish.EventPublish" init-method="publish">
        <property name="eventAdmin" ref="eventAdmin" />
    </bean>
</blueprint>

2.4 接收事件(osgi-event-subscribe)

import org.osgi.service.event.Event;
import org.osgi.service.event.EventHandler;

public class SendEventHandler implements EventHandler {

    public void handleEvent(Event event) {
        System.out.println("=======handleEvent=======");
        System.out.println(event.getTopic());

        for(String key : event.getPropertyNames()) {
            System.out.println(key + "=" + event.getProperty(key));
        }
    }
}

blueprint.xml 配制

<?xml version="1.0" encoding="UTF-8"?>
<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://www.osgi.org/xmlns/blueprint/v1.0.0 http://www.osgi.org/xmlns/blueprint/v1.0.0/blueprint.xsd">

    <service interface="org.osgi.service.event.EventHandler">
        <service-properties>
            <entry key="event.topics" value="send/*"/>
        </service-properties>
        <bean class="com.edu.osgi.event.subscribe.SendEventHandler" />
    </service>
</blueprint>

2.5 karaf 测试

# 查看 EventAdmin 服务是否发布
ls EventAdmin
# 安装 eventadmin
feature:list | grep eventadmin
feature:install eventadmin