BAEL-1596 Spring Events (#5605)

* Annotation-driven event listener + generic events

* update examples + add tests

* add article link

* add more tests for Spring Events

spring-all/src/main/java/org/baeldung/springevents/synchronous/AnnotationDrivenEventListener.java

@@ -0,0 +1,46 @@
+package org.baeldung.springevents.synchronous;
+
+import org.springframework.context.event.ContextStartedEvent;
+import org.springframework.context.event.EventListener;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.event.TransactionPhase;
+import org.springframework.transaction.event.TransactionalEventListener;
+
+@Component
+public class AnnotationDrivenEventListener {
+
+    // for tests
+    private boolean hitContextStartedHandler = false;
+    private boolean hitSuccessfulEventHandler = false;
+    private boolean hitCustomEventHandler = false;
+
+    @EventListener
+    public void handleContextStart(final ContextStartedEvent cse) {
+        System.out.println("Handling context started event.");
+        hitContextStartedHandler = true;
+    }
+
+    @EventListener(condition = "#event.success")
+    public void handleSuccessful(final GenericSpringEvent<String> event) {
+        System.out.println("Handling generic event (conditional): " + event.getWhat());
+        hitSuccessfulEventHandler = true;
+    }
+
+    @TransactionalEventListener(phase = TransactionPhase.BEFORE_COMMIT)
+    public void handleCustom(final CustomSpringEvent event) {
+        System.out.println("Handling event inside a transaction BEFORE COMMIT.");
+        hitCustomEventHandler = true;
+    }
+
+    boolean isHitContextStartedHandler() {
+        return hitContextStartedHandler;
+    }
+
+    boolean isHitSuccessfulEventHandler() {
+        return hitSuccessfulEventHandler;
+    }
+
+    boolean isHitCustomEventHandler() {
+        return hitCustomEventHandler;
+    }
+}

spring-all/src/main/java/org/baeldung/springevents/synchronous/ContextRefreshedListener.java

@@ -7,9 +7,16 @@ import org.springframework.stereotype.Component;
 @Component
 public class ContextRefreshedListener implements ApplicationListener<ContextRefreshedEvent> {
 
+    // for tests
+    private boolean hitContextRefreshedHandler = false;
+
     @Override
     public void onApplicationEvent(final ContextRefreshedEvent cse) {
         System.out.println("Handling context re-freshed event. ");
+        hitContextRefreshedHandler = true;
     }
 
+    boolean isHitContextRefreshedHandler() {
+        return hitContextRefreshedHandler;
+    }
 }

spring-all/src/main/java/org/baeldung/springevents/synchronous/CustomSpringEventPublisher.java

@@ -16,4 +16,16 @@ public class CustomSpringEventPublisher {
         applicationEventPublisher.publishEvent(customSpringEvent);
     }
 
+    public void publishGenericEvent(final String message, boolean success) {
+        System.out.println("Publishing generic event.");
+        final GenericSpringEvent<String> genericSpringEvent = new GenericStringSpringEvent(message, success);
+        applicationEventPublisher.publishEvent(genericSpringEvent);
+    }
+
+    public void publishGenericAppEvent(final String message) {
+        System.out.println("Publishing generic event.");
+        final GenericSpringAppEvent<String> genericSpringEvent = new GenericStringSpringAppEvent(this, message);
+        applicationEventPublisher.publishEvent(genericSpringEvent);
+    }
+
 }

spring-all/src/main/java/org/baeldung/springevents/synchronous/GenericSpringAppEvent.java

@@ -0,0 +1,18 @@
+package org.baeldung.springevents.synchronous;
+
+import org.springframework.context.ApplicationEvent;
+
+public class GenericSpringAppEvent<T> extends ApplicationEvent {
+
+    private final T what;
+
+    public GenericSpringAppEvent(final Object source, final T what) {
+        super(source);
+        this.what = what;
+    }
+
+    public T getWhat() {
+        return what;
+    }
+
+}

spring-all/src/main/java/org/baeldung/springevents/synchronous/GenericSpringEvent.java

@@ -0,0 +1,21 @@
+package org.baeldung.springevents.synchronous;
+
+public class GenericSpringEvent<T> {
+
+    private final T what;
+    protected final boolean success;
+
+    public GenericSpringEvent(final T what, final boolean success) {
+        this.what = what;
+        this.success = success;
+    }
+
+    public T getWhat() {
+        return what;
+    }
+
+    public boolean isSuccess() {
+        return success;
+    }
+
+}

spring-all/src/main/java/org/baeldung/springevents/synchronous/GenericSpringEventListener.java

@@ -0,0 +1,22 @@
+package org.baeldung.springevents.synchronous;
+
+import org.springframework.context.ApplicationListener;
+import org.springframework.lang.NonNull;
+import org.springframework.stereotype.Component;
+
+@Component
+public class GenericSpringEventListener implements ApplicationListener<GenericSpringAppEvent<String>> {
+
+    // for testing
+    private boolean hitEventHandler = false;
+
+    @Override
+    public void onApplicationEvent(@NonNull final GenericSpringAppEvent<String> event) {
+        System.out.println("Received spring generic event - " + event.getWhat());
+        hitEventHandler = true;
+    }
+
+    boolean isHitEventHandler() {
+        return hitEventHandler;
+    }
+}

spring-all/src/main/java/org/baeldung/springevents/synchronous/GenericStringSpringAppEvent.java

@@ -0,0 +1,9 @@
+package org.baeldung.springevents.synchronous;
+
+class GenericStringSpringAppEvent extends GenericSpringAppEvent<String> {
+
+    GenericStringSpringAppEvent(final Object source, final String what) {
+        super(source, what);
+    }
+
+}

spring-all/src/main/java/org/baeldung/springevents/synchronous/GenericStringSpringEvent.java

@@ -0,0 +1,9 @@
+package org.baeldung.springevents.synchronous;
+
+public class GenericStringSpringEvent extends GenericSpringEvent<String> {
+
+    GenericStringSpringEvent(final String what, final boolean success) {
+        super(what, success);
+    }
+
+}