Explicitly Define Singleton Bean Scope

Spring/src/main/java/conference/AppConfig.java

@@ -14,7 +14,7 @@ import org.springframework.context.annotation.Scope;
 public class AppConfig {
 
     @Bean(name = "speakerService")
-    @Scope(value = BeanDefinition.SCOPE_PROTOTYPE)
+    @Scope(value = BeanDefinition.SCOPE_SINGLETON)
     public SpeakerService getSpeakerService() {
         return new SpeakerServiceImpl(getSpeakerRepository());
     }