Refactor: Eliminate duplicate code and optimize database queries (#1)

src/main/java/com/kubuski/urlshortener/controller/AuthenticationController.java

@@ -1,5 +1,6 @@
 package com.kubuski.urlshortener.controller;
 
+import jakarta.validation.Valid;
 import org.springframework.http.HttpStatus;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestBody;
@@ -21,13 +22,13 @@ final class AuthenticationController {
 
     @PostMapping("/register")
     @ResponseStatus(HttpStatus.CREATED)
-    public AuthenticationResponse register(@RequestBody RegisterRequest request) {
+    public AuthenticationResponse register(@Valid @RequestBody RegisterRequest request) {
         return authenticationService.register(request);
     }
 
     @PostMapping("/authenticate")
     @ResponseStatus(HttpStatus.OK)
-    public AuthenticationResponse authenticate(@RequestBody AuthenticationRequest request) {
+    public AuthenticationResponse authenticate(@Valid @RequestBody AuthenticationRequest request) {
         return authenticationService.authenticate(request);
     }
 }

src/main/java/com/kubuski/urlshortener/controller/UrlController.java

@@ -32,7 +32,7 @@ public UrlResponse getOriginalUrl(@PathVariable String shortUrl) {
     @PutMapping("/{shortUrl}")
     @ResponseStatus(HttpStatus.OK)
     public UrlResponse updateOriginalUrl(@PathVariable String shortUrl,
-            @RequestBody UrlRequest urlRequest) {
+            @Valid @RequestBody UrlRequest urlRequest) {
         return urlService.updateOriginalUrl(shortUrl, urlRequest);
     }
 

src/main/java/com/kubuski/urlshortener/controller/UserController.java

@@ -3,6 +3,7 @@
 import com.kubuski.urlshortener.dto.UserRequest;
 import com.kubuski.urlshortener.dto.UserResponse;
 import com.kubuski.urlshortener.service.UserService;
+import jakarta.validation.Valid;
 import lombok.RequiredArgsConstructor;
 import org.springframework.http.HttpStatus;
 import org.springframework.security.access.prepost.PreAuthorize;
@@ -24,7 +25,7 @@ public UserResponse getUserByEmail(@PathVariable String email) {
 
     @PostMapping("/register")
     @ResponseStatus(HttpStatus.CREATED)
-    public UserResponse registerUser(@RequestBody UserRequest userRequest) {
+    public UserResponse registerUser(@Valid @RequestBody UserRequest userRequest) {
         return userService.registerUser(userRequest);
     }
 }

src/main/java/com/kubuski/urlshortener/dto/AuthenticationRequest.java

@@ -1,4 +1,9 @@
 package com.kubuski.urlshortener.dto;
 
-public record AuthenticationRequest(String login, String password) {
+import jakarta.validation.constraints.NotBlank;
+
+public record AuthenticationRequest(
+        @NotBlank(message = "Login is required") String login,
+        @NotBlank(message = "Password is required") String password) {
+
 }

src/main/java/com/kubuski/urlshortener/dto/RegisterRequest.java

@@ -1,7 +1,14 @@
 package com.kubuski.urlshortener.dto;
 
 import com.kubuski.urlshortener.entity.Roles;
+import jakarta.validation.constraints.Email;
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.NotNull;
 
-public record RegisterRequest(String username, String password, String email, Roles role) {
+public record RegisterRequest(
+        @NotBlank(message = "Username is required") String username,
+        @NotBlank(message = "Password is required") String password,
+        @NotBlank(message = "Email is required") @Email(message = "Email should be valid") String email,
+        @NotNull(message = "Role is required") Roles role) {
 
 }

src/main/java/com/kubuski/urlshortener/dto/UrlRequest.java

@@ -1,6 +1,11 @@
 package com.kubuski.urlshortener.dto;
 
-import jakarta.validation.constraints.NotEmpty;
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.Pattern;
+
+public record UrlRequest(
+        @NotBlank(message = "URL is required")
+        @Pattern(regexp = "^https?://.*", message = "URL must start with http:// or https://")
+        String url) {
 
-public record UrlRequest(@NotEmpty String url) {
 }

src/main/java/com/kubuski/urlshortener/dto/UserRequest.java

@@ -1,7 +1,14 @@
 package com.kubuski.urlshortener.dto;
 
 import com.kubuski.urlshortener.entity.Roles;
+import jakarta.validation.constraints.Email;
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.NotNull;
 
-public record UserRequest(String username, String password, String email, Roles role) {
+public record UserRequest(
+        @NotBlank(message = "Username is required") String username,
+        @NotBlank(message = "Password is required") String password,
+        @NotBlank(message = "Email is required") @Email(message = "Email should be valid") String email,
+        @NotNull(message = "Role is required") Roles role) {
 
 }

src/main/java/com/kubuski/urlshortener/exception/BaseException.java

@@ -0,0 +1,11 @@
+package com.kubuski.urlshortener.exception;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.ResponseStatus;
+
+@ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
+public abstract class BaseException extends RuntimeException {
+    protected BaseException(final String message) {
+        super(message);
+    }
+}

src/main/java/com/kubuski/urlshortener/exception/UrlNotFoundException.java

@@ -4,7 +4,7 @@
 import org.springframework.web.bind.annotation.ResponseStatus;
 
 @ResponseStatus(HttpStatus.NOT_FOUND)
-public class UrlNotFoundException extends RuntimeException {
+public class UrlNotFoundException extends BaseException {
     public UrlNotFoundException(final String message) {
         super(message);
     }

src/main/java/com/kubuski/urlshortener/exception/UserAlreadyExistsException.java

@@ -4,7 +4,7 @@
 import org.springframework.web.bind.annotation.ResponseStatus;
 
 @ResponseStatus(HttpStatus.CONFLICT)
-public class UserAlreadyExistsException extends RuntimeException {
+public class UserAlreadyExistsException extends BaseException {
     public UserAlreadyExistsException(String message) {
         super(message);
     }

src/main/java/com/kubuski/urlshortener/exception/UserNotFoundException.java

@@ -4,7 +4,7 @@
 import org.springframework.web.bind.annotation.ResponseStatus;
 
 @ResponseStatus(HttpStatus.NOT_FOUND)
-public class UserNotFoundException extends RuntimeException {
+public class UserNotFoundException extends BaseException {
     public UserNotFoundException(final String message) {
         super(message);
     }

src/main/java/com/kubuski/urlshortener/mapper/EntityMapper.java

@@ -0,0 +1,50 @@
+package com.kubuski.urlshortener.mapper;
+
+import com.kubuski.urlshortener.dto.UrlResponse;
+import com.kubuski.urlshortener.dto.UserResponse;
+import com.kubuski.urlshortener.entity.Url;
+import com.kubuski.urlshortener.entity.User;
+
+/**
+ * Utility class for mapping between entities and DTOs.
+ * Centralizes conversion logic to reduce code duplication.
+ */
+public final class EntityMapper {
+
+    private EntityMapper() {
+        // Utility class, prevent instantiation
+    }
+
+    /**
+     * Converts a User entity to UserResponse DTO.
+     *
+     * @param user the User entity
+     * @return UserResponse DTO
+     */
+    public static UserResponse toUserResponse(User user) {
+        return new UserResponse(
+                user.getId(),
+                user.getUsername(),
+                user.getEmail(),
+                user.getRole()
+        );
+    }
+
+    /**
+     * Converts a Url entity to UrlResponse DTO.
+     *
+     * @param url the Url entity
+     * @return UrlResponse DTO
+     */
+    public static UrlResponse toUrlResponse(Url url) {
+        return new UrlResponse(
+                url.getId(),
+                url.getOriginalUrl(),
+                url.getShortUrl(),
+                url.getCreatedAt(),
+                url.getUpdatedAt(),
+                url.getExpirationDate(),
+                url.getAccessCount()
+        );
+    }
+}

src/main/java/com/kubuski/urlshortener/repository/UrlRepository.java

@@ -8,8 +8,6 @@
 import java.util.Optional;
 
 public interface UrlRepository extends JpaRepository<Url, Long> {
-    Optional<Url> findById(Long id);
-
     Optional<Url> findByShortUrlAndDeletedFalse(String shortUrl);
 
     List<Url> findAllByDeletedTrueAndUpdatedAtBefore(Instant cutoffDate);

src/main/java/com/kubuski/urlshortener/repository/UserRepository.java

@@ -14,4 +14,7 @@ public interface UserRepository extends JpaRepository<User, Long> {
 
     @Query("SELECT u FROM User u WHERE u.email = :login OR u.username = :login")
     Optional<User> findByEmailOrUsername(@Param("login") String login);
+
+    @Query("SELECT COUNT(u) > 0 FROM User u WHERE u.email = :email OR u.username = :username")
+    boolean existsByEmailOrUsername(@Param("email") String email, @Param("username") String username);
 }

src/main/java/com/kubuski/urlshortener/service/AuthenticationService.java

@@ -68,7 +68,6 @@ private void checkIfUserExists(String email, String username) {
     }
 
     private boolean userExists(String email, String username) {
-        return userRepository.findByEmailOrUsername(email).isPresent()
-                || userRepository.findByEmailOrUsername(username).isPresent();
+        return userRepository.existsByEmailOrUsername(email, username);
     }
 }

src/main/java/com/kubuski/urlshortener/service/UrlService.java

@@ -4,6 +4,7 @@
 import com.kubuski.urlshortener.dto.UrlResponse;
 import com.kubuski.urlshortener.entity.Url;
 import com.kubuski.urlshortener.exception.UrlNotFoundException;
+import com.kubuski.urlshortener.mapper.EntityMapper;
 import com.kubuski.urlshortener.repository.UrlRepository;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Service;
@@ -22,23 +23,23 @@ public UrlResponse createShortUrl(UrlRequest urlRequest) {
         Url url = buildUrl(urlRequest);
         Url savedUrl = urlRepository.save(url);
 
-        return toUrlResponse(savedUrl);
+        return EntityMapper.toUrlResponse(savedUrl);
     }
 
     @Transactional
     public UrlResponse getOriginalUrl(String shortUrl) {
         Url url = findUrlByShortUrl(shortUrl);
         incrementAccessCount(url);
 
-        return toUrlResponse(url);
+        return EntityMapper.toUrlResponse(url);
     }
 
     @Transactional
     public UrlResponse updateOriginalUrl(String shortUrl, UrlRequest urlRequest) {
         Url url = findUrlByShortUrl(shortUrl);
         updateUrl(url, urlRequest);
 
-        return toUrlResponse(url);
+        return EntityMapper.toUrlResponse(url);
     }
 
     @Transactional
@@ -51,7 +52,7 @@ public void deleteUrl(String shortUrl) {
     public UrlResponse getUrlStats(String shortUrl) {
         Url url = findUrlByShortUrl(shortUrl);
 
-        return toUrlResponse(url);
+        return EntityMapper.toUrlResponse(url);
     }
 
     private Url buildUrl(UrlRequest urlRequest) {
@@ -80,10 +81,4 @@ private void markUrlAsDeleted(Url url) {
     private String generateShortCode() {
         return UUID.randomUUID().toString().substring(0, 8);
     }
-
-    private UrlResponse toUrlResponse(Url url) {
-        return new UrlResponse(url.getId(), url.getOriginalUrl(), url.getShortUrl(),
-                url.getCreatedAt(), url.getUpdatedAt(), url.getExpirationDate(),
-                url.getAccessCount());
-    }
 }

src/main/java/com/kubuski/urlshortener/service/UserService.java

@@ -4,6 +4,7 @@
 import com.kubuski.urlshortener.dto.UserResponse;
 import com.kubuski.urlshortener.entity.User;
 import com.kubuski.urlshortener.exception.UserNotFoundException;
+import com.kubuski.urlshortener.mapper.EntityMapper;
 import com.kubuski.urlshortener.repository.UserRepository;
 import lombok.RequiredArgsConstructor;
 import org.springframework.security.crypto.password.PasswordEncoder;
@@ -22,23 +23,19 @@ public UserResponse findByEmail(String email) {
         User user = userRepository.findByEmail(email).orElseThrow(
                 () -> new UserNotFoundException("User " + email + " not found in Database"));
 
-        return toUserResponse(user);
+        return EntityMapper.toUserResponse(user);
     }
 
     public UserResponse registerUser(UserRequest userRequest) {
         User user = toUser(userRequest);
         user.setPassword(passwordEncoder.encode(user.getPassword()));
         userRepository.save(user);
 
-        return toUserResponse(user);
+        return EntityMapper.toUserResponse(user);
     }
 
     private User toUser(UserRequest userRequest) {
         return User.builder().username(userRequest.username()).password(userRequest.password())
                 .email(userRequest.email()).role(userRequest.role()).build();
     }
-
-    private UserResponse toUserResponse(User user) {
-        return new UserResponse(user.getId(), user.getUsername(), user.getEmail(), user.getRole());
-    }
 }