Spring文档苦读【ApplicationEvent】

简介

　　首先，要说一下ApplicationEvent是干什么用的！

　　个人理解，就是Spring管理的发布/订阅器，主要用来触发一系列Spring 内部事件。

　　内部事件在Spring文档苦读【1】有介绍。

如何自己定义发布/订阅器

　　下面我就写一个小例子，主要是用来发送邮件的。（该例子取自Spring官方文档）

　　首先，要创建一个事件<ApplicationEvent>，交有Spring管理

public class BlackListEvent extends ApplicationEvent {
    private final String address;
    private final String test;
    public BlackListEvent(Object source, String test, String address) {
        super(source);
        this.address = address;
        this.test = test;
    }
    public String getAddress() {
        return address;
    }


    public String getTest() {
        return test;
    }


    private static final long serialVersionUID = 1L;

}

　　其次创建一个通知监听器<ApplicationListener>.

public class BlackListNotifier implements ApplicationListener<BlackListEvent> {

    private String notificationAddress;

    public void setNotificationAddress(String notificationAddress) {
        this.notificationAddress = notificationAddress;
    }

    public void onApplicationEvent(BlackListEvent event) {
        System.out.println("onApplicationEvent +"+event.getAddress());
        System.out.println("to send email");
    }

}

　　最后，创建Service，要继承<ApplicationEventPublisherAware>,以便获取ApplicationEventPublisher

public class EmailService implements ApplicationEventPublisherAware {

    private List<String> blackList;
    private ApplicationEventPublisher publisher;

    public void setBlackList(List<String> blackList) {
        this.blackList = blackList;
    }

    public void setApplicationEventPublisher(ApplicationEventPublisher publisher) {
        this.publisher = publisher;
    }

    public void sendEmail(String address, String text) {
        if (blackList.contains(address)) {
            BlackListEvent event = new BlackListEvent(this, address, text);

            System.out.println("发布事件begin");
            publisher.publishEvent(event);
            System.out.println("发布事件end");
            return;
        }
    }
}

　　编写xml

<bean id="emailService" class="com.may.web.event.EmailService">
        <property name="blackList">
            <list>
                <value>known.spammer@example.org</value>
                <value>known.hacker@example.org</value>
                <value>john.doe@example.org</value>
            </list>
        </property>
    </bean>
    
    <bean id="blackListNotifier" class="com.may.web.event.BlackListNotifier">
        <property name="notificationAddress" value="blacklist@example.org"/>
    </bean>

　　最后测试

@RunWith(SpringRunner.class)
@ContextConfiguration("/beans.xml")
public class XmlApplicationContextTests {
    @Autowired
    private ApplicationContext applicationContext;
    @Test
    public void testEvent() {
        EmailService service = applicationContext.getBean("emailService", EmailService.class);
        service.sendEmail("known.spammer@example.org", "111111");
    }
}

　　输出

发布事件begin
onApplicationEvent +111111
to send email
发布事件end