Add EventListener example

spring-all/src/main/java/org/baeldung/startup/EventListenerExampleBean.java

@@ -0,0 +1,19 @@
+package org.baeldung.startup;
+
+import org.apache.log4j.Logger;
+import org.springframework.context.event.ContextRefreshedEvent;
+import org.springframework.context.event.EventListener;
+import org.springframework.stereotype.Component;
+
+@Component
+public class EventListenerExampleBean {
+    private static final Logger LOG = Logger.getLogger(EventListenerExampleBean.class);
+
+    public static int counter;
+
+    @EventListener
+    public void onApplicationEvent(ContextRefreshedEvent event) {
+        LOG.info("Increment counter");
+        counter++;
+    }
+}