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

(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 id="eventAdmin" interface="org.osgi.service.event.EventAdmin" />

    <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

注意： osgi-event-subscribe 只能处理启动后发布的事件，不能处理启动前的事件。

3. 事件过滤

3.1 基于主题的过滤

<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>

3.2 基于内容的过滤

<service interface="org.osgi.service.event.EventHandler">

    <service-properties>

        <entry key="event.topics" value="send/*"/>

        <entry key="event.filter" value="(phone=10010)"/>

    </service-properties>

    <bean class="com.edu.osgi.event.subscribe.SendEventHandler" />

</service>

OSGi 系列（十四）之 Event Admin Service的相关教程结束。