BAEL-3828 Where Should @Service Annotation Be Kept? (#10430)

* BAEL-3828 add code samples and tests for the article

* BAEL-3828 fix maven test folder structure and test executions

* BAEL-3828 fix indentation in continuation lines

spring-boot-modules/spring-boot-annotations/src/main/java/com/baeldung/annotations/service/AuthApplication.java

@@ -0,0 +1,22 @@
+package com.baeldung.annotations.service;
+
+import com.baeldung.annotations.service.abstracts.AbstractAuthenticationService;
+import com.baeldung.annotations.service.interfaces.AuthenticationService;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class AuthApplication {
+
+    @Autowired
+    private AuthenticationService inMemoryAuthService;
+
+    @Autowired
+    private AbstractAuthenticationService ldapAuthService;
+
+    public static void main(String[] args) {
+        SpringApplication.run(AuthApplication.class, args);
+    }
+
+}

spring-boot-modules/spring-boot-annotations/src/main/java/com/baeldung/annotations/service/abstracts/AbstractAuthenticationService.java

@@ -0,0 +1,12 @@
+package com.baeldung.annotations.service.abstracts;
+
+import org.springframework.stereotype.Service;
+
+@Service
+public abstract class AbstractAuthenticationService {
+
+    public boolean authenticate(String username, String password) {
+        return false;
+    }
+
+}

spring-boot-modules/spring-boot-annotations/src/main/java/com/baeldung/annotations/service/concretes/InMemoryAuthenticationService.java

@@ -0,0 +1,14 @@
+package com.baeldung.annotations.service.concretes;
+
+import com.baeldung.annotations.service.interfaces.AuthenticationService;
+import org.springframework.stereotype.Service;
+
+@Service
+public class InMemoryAuthenticationService implements AuthenticationService {
+
+    @Override
+    public boolean authenticate(String username, String password) {
+        return false;
+    }
+
+}

spring-boot-modules/spring-boot-annotations/src/main/java/com/baeldung/annotations/service/concretes/LdapAuthenticationService.java

@@ -0,0 +1,14 @@
+package com.baeldung.annotations.service.concretes;
+
+import com.baeldung.annotations.service.abstracts.AbstractAuthenticationService;
+import org.springframework.stereotype.Service;
+
+@Service
+public class LdapAuthenticationService extends AbstractAuthenticationService {
+
+    @Override
+    public boolean authenticate(String username, String password) {
+        return true;
+    }
+
+}

spring-boot-modules/spring-boot-annotations/src/main/java/com/baeldung/annotations/service/interfaces/AuthenticationService.java

@@ -0,0 +1,10 @@
+package com.baeldung.annotations.service.interfaces;
+
+import org.springframework.stereotype.Service;
+
+@Service
+public interface AuthenticationService {
+
+    boolean authenticate(String username, String password);
+
+}