定義一個事件，因SPRING中可以有不同的事件，需要定義一個類以作區分：
import lombok.Getter;
import org.springframework.context.ApplicationEvent;
@Getter
public class JavaStackEvent extends ApplicationEvent {
/**
* Create a new {@code ApplicationEvent}.
*
* @param source the object on which the event initially occurred or with
* which the event is associated (never {@code null})
*/
public JavaStackEvent(Object source) {
super(source);
}
}
定義一個此事件觀察者，即感興趣者：
import lombok.NonNull;
import lombok.RequiredArgsConstructor;
import org.springframework.context.ApplicationListener;
import org.springframework.scheduling.annotation.Async;
/**
* 觀察者：讀者粉絲
*/
@RequiredArgsConstructor
public class ReaderListener implements ApplicationListener<JavaStackEvent> {
@NonNull
private String name;
private String article;
@Async
@Override
public void onApplicationEvent(JavaStackEvent event) {
// 更新文章
updateArticle(event);
}
private void updateArticle(JavaStackEvent event) {
this.article = (String) event.getSource();
System.out.printf("我是讀者：%s，文章已更新為：%s\n", this.name, this.article);
}
}
注冊感興趣者（將自身注入SPRING容器則完成注冊），并制定發布機制（通過CONTEXT發布事件）：
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.CommandLineRunner;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Slf4j
@Configuration
public class ObserverConfiguration {
@Bean
public CommandLineRunner commandLineRunner(ApplicationContext context) {
return (args) -> {
log.info("發布事件：什么是觀察者模式？");
context.publishEvent(new JavaStackEvent("什么是觀察者模式？"));
};
}
@Bean
public ReaderListener readerListener1(){
return new ReaderListener("小明");
}
@Bean
public ReaderListener readerListener2(){
return new ReaderListener("小張");
}
@Bean
public ReaderListener readerListener3(){
return new ReaderListener("小愛");
}
}