springboot 事件监听（ApplicationListener实现）

桃扇骨 2023-02-23 01:30 36阅读 0赞

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### springboot 事件监听（ApplicationListener实现） ###

**事件：实现bean与bean之间的通信，当一个bean处理完后，另一个bean做相应的处理**

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**相关类与接口**

**ApplicationEvent**

public abstract class ApplicationEvent extends EventObject {
        private static final long serialVersionUID = 7099057708183571937L;
        private final long timestamp = System.currentTimeMillis();
    
        public ApplicationEvent(Object source) {
            super(source);
        }
    
        public final long getTimestamp() {
            return this.timestamp;
        }
    }

**ApplicationEventPublisher：事件发布**

@FunctionalInterface
    public interface ApplicationEventPublisher {
        default void publishEvent(ApplicationEvent event) {
            this.publishEvent((Object)event);
        }
    
        void publishEvent(Object var1);
    }

**ApplicationContext：该接口实现了ApplicationEventPublisher**

public interface ApplicationContext extends EnvironmentCapable, ListableBeanFactory, HierarchicalBeanFactory, MessageSource, ApplicationEventPublisher, ResourcePatternResolver {
        @Nullable
        String getId();
    
        String getApplicationName();
    
        String getDisplayName();
    
        long getStartupDate();
    
        @Nullable
        ApplicationContext getParent();
    
        AutowireCapableBeanFactory getAutowireCapableBeanFactory() throws IllegalStateException;
    }

**ApplicationListener：事件监听**

@FunctionalInterface
    public interface ApplicationListener<E extends ApplicationEvent> extends EventListener {
        void onApplicationEvent(E var1);
    }

**EventListener**

public interface EventListener {
    }

**@EventListener**

@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface EventListener {
        @AliasFor("classes")
        Class<?>[] value() default {};
    
        @AliasFor("value")
        Class<?>[] classes() default {};
    
        String condition() default "";
    }

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**示例**

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**event **

**CustomEvent**

public class CustomEvent extends ApplicationEvent {
    
        private String message;
    
        public CustomEvent(Object source,String message){
            super(source);
            this.message=message;
        }
    
        public String getMessage() {
            return message;
        }
    
        public void setMessage(String message) {
            this.message = message;
        }
    }

**CustomEventListener**

@Component
    public class CustomEventListener implements ApplicationListener<CustomEvent> {
    
        @Override
        public void onApplicationEvent(CustomEvent customEvent) {
            System.out.println("监听器接受消息："+System.currentTimeMillis());
            System.out.println("接收到事件消息："+customEvent.getMessage());
        }
    }

**\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\***

**controller 层**

**HelloController**

@RestController
    public class HelloController {
    
        @Resource
        private ApplicationContext applicationContext;
    
        @RequestMapping("/hello")
        public String hello(){
            System.out.println("事件开始发布消息："+System.currentTimeMillis());
            applicationContext.publishEvent(new CustomEvent(this,"你好啊"));
    
            return "success";
        }
    }

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**使用测试**

**localhost:8080/hello**

2020-07-05 10:02:34.267  INFO 22504 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
    2020-07-05 10:02:34.273  INFO 22504 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 6 ms
    事件开始发布消息：1593914554286
    监听器接受消息：1593914554286
    接收到事件消息：你好啊