Simple event handling library!
This project composes of components for implementing the event handling parts of the DDD/CQRS pattern. This library was built with simplicity, modularity and pluggability in mind.
- Send events to one or many registered event handlers.
- Multiple ways of registering event handlers:
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Simple registration (no IoC container).
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IoC container registration
- achieved by creating implementations of EventHandlerProvider:
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Spring Context
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Guice
-
- achieved by creating implementations of EventHandlerProvider:
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Attribute registration (Soon!)
- achieved by marking methods with @EventHandler annotations.
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You can simply clone this repository, build the source, reference the jar from your project, and code away!
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XerJ.EventStack is also available in the Maven Central:
// Example command.
public class ProductRegisteredEvent
{
private final int productId;
private final String productName;
public ProductRegisteredEvent(int productId, String productName)
{
this.productId = productId;
this.productName = productName;
}
public int getProductId() {
return productId;
}
public String getProductName() {
return productName;
}
}
// Event handler 1.
public class ProductRegisteredNotificationHandler : EventHandler<ProductRegisteredEvent>
{
private final NotificationService notificationService;
public ProductRegisteredNotificationHandler(NotificationService notificationService)
{
this.notificationService = notificationService;
}
@Override
public CompletableFuture<Void> handle(ProductRegisteredEvent event)
{
return notificationService.notify("Product registered! - " + event.getProductName());
}
}
... Other event handlersBefore we can dispatch any events, first we need to register our event handlers. There are several ways to do this:
public static void main(String[] args)
{
RegistryEventHandlerProvider provider = new RegistryEventHandlerProvider(registry -> {
registry.registerEventHandler(ProductRegisteredEvent.class, () -> new ProductRegisteredNotificationHandler(
new EmailNotificationService()
));
});
EventDispatcher dispatcher = new EventDispatcher(provider);
// Dispatch event.
CompletableFuture<Void> future = dispatcher.send(new ProductRegisteredEvent(1, "My Product Name"));
}Spring Context
public static void main(String[] args)
{
ApplicationContext appContext = new AnnotationConfigApplicationContext(BeanConfigs.class);
SpringContextEventHandlerPovider provider = new SpringContextEventHandlerPovider(appContext);
EventDispatcher dispatcher = new EventDispatcher(provider);
// Dispatch event.
CompletableFuture<Void> future = dispatcher.send(new ProductRegisteredEvent(1, "My Product Name"));
}Guice
public static void main(String[] args)
{
Injector injector = Guice.createInjector(new AppModule());
GuiceEventHandlerPovider provider = new GuiceEventHandlerPovider(injector);
EventDispatcher dispatcher = new EventDispatcher(provider);
// Dispatch event.
CompletableFuture<Void> future = dispatcher.send(new ProductRegisteredEvent(1, "My Product Name"));
}
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