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编程网其它相关文章!