SpringBoot实现自定义事件的方法详解
目录
- 简介
- 步骤1:自定义事件
- 步骤2:自定义监听器
- 方案1:ApplicationListener
- 方案2:SmartApplicationListener
- 步骤3:注册监听器
- 法1:@Component(适用于所有监听器)
- 法2:application.yml中添加配置
- 法3:启动类中注册
- 步骤4:发布事件
- 法1:注入ApplicationContext,调用其publishEvent方法
- 法2:启动类中发布
简介
说明
本文用实例来介绍如何在SpringBoot中自定义事件来使用观察者模式。
事件的顺序
可使用实现Ordered接口的方式,调整监听器顺序。
注意:必须是同时实现 ApplicationListener<MyEvent>,Ordered这样的方法才能控制顺序。
下边几种都是无法控制顺序的:
- @Component+@EventListerner+实现Ordered
- 实现 ApplicationListener<MyEvent>+@Order
步骤1:自定义事件
通过继承ApplicationEvent来自定义事件。
构造器的参数为该事件的相关数据对象,监听器可以获取到该数据对象,进而进行相关逻辑处理。
package com.example.event; import org.springframework.context.ApplicationEvent; public class MyEvent extends ApplicationEvent { public MyEvent(Object source) { super(source); } }
步骤2:自定义监听器
方案1:ApplicationListener
法1:@EventListener
监听单个事件
package com.example.event; import org.springframework.context.event.EventListener; import org.springframework.stereotype.Component; public class MyListener { @EventListener public void abc(MyEvent event) { System.out.println("监听器: " + "MyListener"); System.out.println(" 线程: " + Thread.currentThread().getName()); System.out.println(" 事件: " + event); System.out.println(" 事件的数据:" + event.getSource()); } }
或者
package com.example.event; import org.springframework.context.ApplicationEvent; import org.springframework.context.event.EventListener; import org.springframework.stereotype.Component; public class MyListener { @EventListener({MyEvent.class}) public void abc(ApplicationEventevent) { System.out.println("监听器: " + "MyListener"); System.out.println(" 线程: " + Thread.currentThread().getName()); System.out.println(" 事件: " + event); System.out.println(" 事件的数据: " + event.getSource()); } }
上边的办法比较好,因为不需要类型转换了。直接就能确定是MyEvent类型。
监听多个事件
事件进来之后,可以使用if(event instanceOf MyEvent.class)来判断是哪种事件。
package com.example.event; import org.springframework.context.ApplicationEvent; import org.springframework.context.event.EventListener; import org.springframework.stereotype.Component; @Component public class MyListener { @EventListener({MyEvent.class, MyEvent2.class}) public void abc(ApplicationEvent event) { System.out.println("监听器: " + "MyListener"); System.out.println(" 所在线程: " + Thread.currentThread().getName()); System.out.println(" 事件: " + event); System.out.println(" 事件的数据:" + event.getSource()); } }
监听所有ApplicationEvent
若使用这种写法,启动时会打印很多Spring自带的事件。任意ApplicationEvent都会进入这里边。
package com.example.event; import org.springframework.context.ApplicationEvent; import org.springframework.context.event.EventListener; import org.springframework.stereotype.Component; @Component public class MyListener { @EventListener public void abc(ApplicationEvent event) { System.out.println("监听器: " + "MyListener"); System.out.println(" 所在线程: " + Thread.currentThread().getName()); System.out.println(" 事件: " + event); System.out.println(" 事件的数据:" + event.getSource()); } }
法2:实现ApplicationListener<T>接口
public class MyListener implements ApplicationListener<MyEvent>{ public void onApplicationEvent(MyEvent event){ System.out.println("监听器: " + "MyListener"); System.out.println(" 所在线程: " + Thread.currentThread().getName()); System.out.println(" 事件: " + event); System.out.println(" 事件的数据:" + event.getSource()); } }
方案2:SmartApplicationListener
源码如下
public interface SmartApplicationListener extends ApplicationListener<ApplicationEvent>, Ordered { boolean supportsEventType(Class<? extends ApplicationEvent> var1); default boolean supportsSourceType(@Nullable Class<?> sourceType) { return true; } default int getOrder() { return 2147483647; } }
supportsEventType:支持的事件的类型
supportsSourceType:支持的数据的类型
getOrder:2147483641:是2^31-1,也就是32位的int的最大正数 。
示例
事件
package com.example.event; import org.springframework.context.ApplicationEvent; public class MyEvent extends ApplicationEvent { public MyEvent(Object source) { super(source); } }
监听器1
package com.example.event; import org.springframework.context.ApplicationEvent; import org.springframework.context.event.SmartApplicationListener; import org.springframework.stereotype.Component; @Component public class MyListener implements SmartApplicationListener { @Override public boolean supportsEventType(Class<? extends ApplicationEvent> aClass) { return aClass == MyEvent.class; } @Override public boolean supportsSourceType(Class<?> sourceType) { return sourceType == String.class; } @Override public int getOrder() { return 2; } @Override public void onApplicationEvent(ApplicationEvent event) { System.out.println("监听器: " + "MyListener"); System.out.println(" 所在线程: " + Thread.currentThread().getName()); System.out.println(" 事件: " + event); System.out.println(" 事件的数据:" + event.getSource()); System.out.println(" 是MyEvent?:" + (event instanceof MyEvent)); } }
监听器2
package com.example.event; import org.springframework.context.ApplicationEvent; import org.springframework.context.event.SmartApplicationListener; import org.springframework.stereotype.Component; @Component public class MyListener2 implements SmartApplicationListener { @Override public boolean supportsEventType(Class<? extends ApplicationEvent> aClass) { return aClass == MyEvent.class; } @Override public boolean supportsSourceType(Class<?> sourceType) { return sourceType == String.class; } @Override public int getOrder() { return 1; } @Override public void onApplicationEvent(ApplicationEvent event) { System.out.println("监听器: " + "MyListener2"); System.out.println(" 所在线程: " + Thread.currentThread().getName()); System.out.println(" 事件: " + event); System.out.println(" 事件的数据:" + event.getSource()); System.out.println(" 是MyEvent?:" + (event instanceof MyEvent)); } }
发布器
package com.example.event; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.ApplicationContext; import org.springframework.stereotype.Component; @Component public class MyPublisher { @Autowired ApplicationContext applicationContext; public void myPublish(String message) { System.out.println("发布器所在线程:" + Thread.currentThread().getName()); applicationContext.publishEvent(new MyEvent(message)); } }
测试
package com.example.controller; import com.example.event.MyPublisher; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; @RestController public class HelloController { @Autowired MyPublisher myPublisher; @GetMapping("/test1") public String test1() { myPublisher.myPublish("Hello"); return "test1 success"; } }
启动后,访问:http://localhost:8080/test1
后端输出:
发布器所在线程:http-nio-8080-exec-2
监听器: MyListener2
所在线程: http-nio-8080-exec-2
事件: com.example.event.MyEvent[source=Hello]
事件的数据:Hello
是MyEvent?:true
监听器: MyListener
所在线程: http-nio-8080-exec-2
事件: com.example.event.MyEvent[source=Hello]
事件的数据:Hello
是MyEvent?:true
如果将监听器的实现的Ordered顺序颠倒,则输出结果如下:
发布器所在线程:http-nio-8080-exec-1
监听器: MyListener
所在线程: http-nio-8080-exec-1
事件: com.example.event.MyEvent[source=Hello]
事件的数据:Hello
是MyEvent?:true
监听器: MyListener2
所在线程: http-nio-8080-exec-1
事件: com.example.event.MyEvent[source=Hello]
事件的数据:Hello
是MyEvent?:true
步骤3:注册监听器
方式 | 适用范围 | 能否搭配@Async注解,进行异步监听 |
---|---|---|
@Component | 所有监听器 | 能 |
application.yml中添加配置 | 实现ApplicationListener<T>接口的监听器 | 不能 |
启动类中注册 | 实现ApplicationListener<T>接口的监听器 | 不能 |
法1:@Component(适用于所有监听器)
package com.example.event; import org.springframework.context.event.EventListener; import org.springframework.stereotype.Component; @Component public class MyListener { @EventListener public void abc(MyEvent event) { System.out.println("监听器:" + "MyListener"); System.out.println("线程:" + Thread.currentThread().getName()); System.out.println("事件:" + event); System.out.println("事件的数据:" + event.getSource()); } }
package com.example.event; import org.springframework.context.ApplicationListener; import org.springframework.stereotype.Component; @Component public class MyListener2 implements ApplicationListener<MyEvent> { @Override public void onApplicationEvent(MyEvent event) { System.out.println("监听器:" + "MyListener2"); System.out.println("线程:" + Thread.currentThread().getName()); System.out.println("事件:" + event); System.out.println("事件的数据:" + event.getSource()); } }
法2:application.yml中添加配置
只适用于实现ApplicationListener<T>接口的监听器
context:
listener:
classes: com.example.event.MyListener,com.example.event.MyListener2
法3:启动类中注册
只适用于实现ApplicationListener<T>接口的监听器
package com.example; import com.example.event.MyListener; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.context.ConfigurableApplicationContext; @SpringBootApplication public class DemoApplication { public static void main(String[] args) { // 原来是这样的:SpringApplication.run(DemoApplication.class, args); ConfigurableApplicationContext context = SpringApplication.run(DemoApplication.class, args); context.addApplicationListener(new MyListener()); } }
步骤4:发布事件
法1:注入ApplicationContext,调用其publishEvent方法
package com.example.event; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.ApplicationContext; import org.springframework.stereotype.Component; @Component public class MyPublisher { @Autowired ApplicationContext applicationContext; public void myPublish(String message) { applicationContext.publishEvent(new MyEvent(message)); } }
法2:启动类中发布
package com.example; import com.example.event.MyEvent; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.context.ConfigurableApplicationContext; @SpringBootApplication public class DemoApplication { public static void main(String[] args) { //原来是:SpringApplication.run(DemoApplication.class, args); ConfigurableApplicationContext context =SpringApplication.run(DemoApplication.class, args); context.publishEvent(new MyEvent("Hello")); } }
以上就是SpringBoot实现自定义事件的方法详解的详细内容,更多关于SpringBoot自定义事件的资料请关注我们其它相关文章!