ApplicationEventPublisher is not being autowired into Component - spring

Question

I have a Spring Boot app and #Component class which looks like:
#Component
public class CustomEvent {
#Autowired
ApplicationEventPublisher publisher;
#PreRemove
public void onItemDelete(Object entity) {
System.out.println(" =======PUBLISH====== " + entity);
publisher.publishEvent(new EntityDeleteEvent<>(entity));
}
}
When it goes to run above method the first line is printed with proper entity but the publisher.publishEvent line throws a NullPointerException. I suppose it that the ApplicationEventPublisher is not being #Autowired but couldn't find why. Other #Components which are in the app are found by #ComponentScanner.
Of course in my entity this CustomEvent is registered:
#Entity
#EntityListeners(
CustomEvent.class
)
#Data
#AllArgsConstructor
public class Item
The exact error which is thrown looks like:
2017-10-26 16:46:06.190 ERROR 10176 --- [io-8091-exec-10] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException: null
at com.inventory.events.CustomEvent.onItemDelete(CustomEvent.java:19)
Do you have any suggestion why publisher is null?

Answer 1

The initialisation of ApplicationEventPublisher doesn't happen OR will remain null, if you have created the CustomeEvent without the help of Bean (like CustomEvent event = new CustomEvent().
Instead, declare the CustomEvent as bean in your configuration (Spring) and get the CustomEvent using application context.

Answer 2

If CustomEvent is in the Spring's package scan, then I don't know.
But, there is an additional solution.
Create a class to instantiate spring managed class, but by ApplicationContext.
1 - Create the class below:
public class AppContextUtil implements ApplicationContextAware {
private static ApplicationContext context;
#Override
public void setApplicationContext(ApplicationContext appContext) throws BeansException {
context = appContext;
}
public static ApplicationContext getApplicationContext() {
return context;
}
public static <T> T getBean(Class<T> classe) {
return context.getBean(classe);
}
}
2 - Instance class as below:
public class CustomEvent {
private ApplicationEventPublisher publisher;
#PreRemove
public void onItemDelete(Object entity) {
System.out.println(" =======PUBLISH====== " + entity);
getApplicationEventPublisher().publishEvent(new EntityDeleteEvent<>(entity));
}
private ApplicationEventPublisher getApplicationEventPublisher() {
return AppContextUtil.getBean(ApplicationEventPublisher.class);
}
}