Phase 6 refactor

CODE_REFACTOR_PLAN.md

@@ -210,7 +210,7 @@ all identified issues with an aggressive approach to modernization.
 
 ## Phase 5: Security Enhancements (Days 10-11)
 
-### 5.1 JWT Authentication Filter Improvements ⬜
+### 5.1 JWT Authentication Filter Improvements ✅
 
 **File**: `JwtAuthenticationFilter.java`
 
@@ -224,7 +224,7 @@ all identified issues with an aggressive approach to modernization.
 
 **Breaking Changes**: None (internal improvements)
 
-### 5.2 JWT Entry Point ⬜
+### 5.2 JWT Entry Point ✅
 
 **File**: `JwtAuthenticationEntryPoint.java`
 
@@ -240,7 +240,7 @@ all identified issues with an aggressive approach to modernization.
 
 ## Phase 6: Functional Programming Patterns (Days 12-13)
 
-### 6.1 Mapper Enhancements ⬜
+### 6.1 Mapper Enhancements ✅
 
 **File**: `UserMapper.java`
 
@@ -253,7 +253,7 @@ all identified issues with an aggressive approach to modernization.
 
 **Breaking Changes**: Return type changes to Optional (BREAKING)
 
-### 6.2 Service Method Signatures ⬜
+### 6.2 Service Method Signatures ✅
 
 **Files**: All service classes
 
@@ -267,7 +267,7 @@ all identified issues with an aggressive approach to modernization.
 
 **Breaking Changes**: Method signatures change (BREAKING)
 
-### 6.3 DTO Enhancements ⬜
+### 6.3 DTO Enhancements ✅
 
 **Files**: All DTO records
 

src/main/java/org/nkcoder/dto/auth/LoginRequest.java

@@ -1,8 +1,12 @@
 package org.nkcoder.dto.auth;
 
+import static org.nkcoder.validation.ValidationMessages.EMAIL_INVALID;
+import static org.nkcoder.validation.ValidationMessages.EMAIL_REQUIRED;
+import static org.nkcoder.validation.ValidationMessages.PASSWORD_REQUIRED;
+
 import jakarta.validation.constraints.Email;
 import jakarta.validation.constraints.NotBlank;
 
 public record LoginRequest(
-    @NotBlank(message = "Email is required") @Email(message = "Please provide a valid email") String email,
-    @NotBlank(message = "Password is required") String password) {}
+    @NotBlank(message = EMAIL_REQUIRED) @Email(message = EMAIL_INVALID) String email,
+    @NotBlank(message = PASSWORD_REQUIRED) String password) {}

src/main/java/org/nkcoder/dto/auth/RefreshTokenRequest.java

@@ -1,6 +1,8 @@
 package org.nkcoder.dto.auth;
 
+import static org.nkcoder.validation.ValidationMessages.REFRESH_TOKEN_REQUIRED;
+
 import jakarta.validation.constraints.NotBlank;
 
 public record RefreshTokenRequest(
-    @NotBlank(message = "Refresh token is required") String refreshToken) {}
+    @NotBlank(message = REFRESH_TOKEN_REQUIRED) String refreshToken) {}

src/main/java/org/nkcoder/dto/auth/RegisterRequest.java

@@ -1,10 +1,16 @@
 package org.nkcoder.dto.auth;
 
-import static org.nkcoder.validation.PasswordValidation.COMPLEXITY_PATTERN;
-import static org.nkcoder.validation.PasswordValidation.MIN_LENGTH;
-import static org.nkcoder.validation.PasswordValidation.PASSWORD_COMPLEXITY;
-import static org.nkcoder.validation.PasswordValidation.PASSWORD_MIN_LENGTH;
-import static org.nkcoder.validation.PasswordValidation.PASSWORD_REQUIRED;
+import static org.nkcoder.validation.ValidationMessages.EMAIL_INVALID;
+import static org.nkcoder.validation.ValidationMessages.EMAIL_REQUIRED;
+import static org.nkcoder.validation.ValidationMessages.NAME_MAX_LENGTH;
+import static org.nkcoder.validation.ValidationMessages.NAME_MIN_LENGTH;
+import static org.nkcoder.validation.ValidationMessages.NAME_REQUIRED;
+import static org.nkcoder.validation.ValidationMessages.NAME_SIZE;
+import static org.nkcoder.validation.ValidationMessages.PASSWORD_COMPLEXITY;
+import static org.nkcoder.validation.ValidationMessages.PASSWORD_COMPLEXITY_PATTERN;
+import static org.nkcoder.validation.ValidationMessages.PASSWORD_MIN_LENGTH;
+import static org.nkcoder.validation.ValidationMessages.PASSWORD_REQUIRED;
+import static org.nkcoder.validation.ValidationMessages.PASSWORD_SIZE;
 
 import jakarta.validation.constraints.Email;
 import jakarta.validation.constraints.NotBlank;
@@ -13,7 +19,17 @@
 import org.nkcoder.enums.Role;
 
 public record RegisterRequest(
-    @NotBlank(message = "Email is required") @Email(message = "Please provide a valid email") String email,
-    @NotBlank(message = PASSWORD_REQUIRED) @Size(min = MIN_LENGTH, message = PASSWORD_MIN_LENGTH) @Pattern(regexp = COMPLEXITY_PATTERN, message = PASSWORD_COMPLEXITY) String password,
-    @NotBlank(message = "Name is required") @Size(min = 2, max = 50, message = "Name must be between 2 and 50 " + "characters") String name,
-    Role role) {}
+    @NotBlank(message = EMAIL_REQUIRED) @Email(message = EMAIL_INVALID) String email,
+    @NotBlank(message = PASSWORD_REQUIRED) @Size(min = PASSWORD_MIN_LENGTH, message = PASSWORD_SIZE) @Pattern(regexp = PASSWORD_COMPLEXITY_PATTERN, message = PASSWORD_COMPLEXITY) String password,
+    @NotBlank(message = NAME_REQUIRED) @Size(min = NAME_MIN_LENGTH, max = NAME_MAX_LENGTH, message = NAME_SIZE) String name,
+    Role role) {
+  // Compact constructor that normalizes email to lowercase
+  public RegisterRequest {
+    if (email != null) {
+      email = email.toLowerCase().trim();
+    }
+    if (name != null) {
+      name = name.trim();
+    }
+  }
+}

src/main/java/org/nkcoder/dto/user/ChangePasswordRequest.java

@@ -1,12 +1,12 @@
 package org.nkcoder.dto.user;
 
-import static org.nkcoder.validation.PasswordValidation.COMPLEXITY_PATTERN;
-import static org.nkcoder.validation.PasswordValidation.CONFIRM_PASSWORD_REQUIRED;
-import static org.nkcoder.validation.PasswordValidation.CURRENT_PASSWORD_REQUIRED;
-import static org.nkcoder.validation.PasswordValidation.MIN_LENGTH;
-import static org.nkcoder.validation.PasswordValidation.PASSWORD_COMPLEXITY;
-import static org.nkcoder.validation.PasswordValidation.PASSWORD_MIN_LENGTH;
-import static org.nkcoder.validation.PasswordValidation.PASSWORD_REQUIRED;
+import static org.nkcoder.validation.ValidationMessages.CONFIRM_PASSWORD_REQUIRED;
+import static org.nkcoder.validation.ValidationMessages.CURRENT_PASSWORD_REQUIRED;
+import static org.nkcoder.validation.ValidationMessages.PASSWORD_COMPLEXITY;
+import static org.nkcoder.validation.ValidationMessages.PASSWORD_COMPLEXITY_PATTERN;
+import static org.nkcoder.validation.ValidationMessages.PASSWORD_MIN_LENGTH;
+import static org.nkcoder.validation.ValidationMessages.PASSWORD_REQUIRED;
+import static org.nkcoder.validation.ValidationMessages.PASSWORD_SIZE;
 
 import jakarta.validation.constraints.NotBlank;
 import jakarta.validation.constraints.Pattern;
@@ -16,5 +16,5 @@
 @PasswordMatch
 public record ChangePasswordRequest(
     @NotBlank(message = CURRENT_PASSWORD_REQUIRED) String currentPassword,
-    @NotBlank(message = PASSWORD_REQUIRED) @Size(min = MIN_LENGTH, message = PASSWORD_MIN_LENGTH) @Pattern(regexp = COMPLEXITY_PATTERN, message = PASSWORD_COMPLEXITY) String newPassword,
+    @NotBlank(message = PASSWORD_REQUIRED) @Size(min = PASSWORD_MIN_LENGTH, message = PASSWORD_SIZE) @Pattern(regexp = PASSWORD_COMPLEXITY_PATTERN, message = PASSWORD_COMPLEXITY) String newPassword,
     @NotBlank(message = CONFIRM_PASSWORD_REQUIRED) String confirmPassword) {}

src/main/java/org/nkcoder/dto/user/UpdateProfileRequest.java

@@ -1,8 +1,13 @@
 package org.nkcoder.dto.user;
 
+import static org.nkcoder.validation.ValidationMessages.EMAIL_INVALID;
+import static org.nkcoder.validation.ValidationMessages.NAME_MAX_LENGTH;
+import static org.nkcoder.validation.ValidationMessages.NAME_MIN_LENGTH;
+import static org.nkcoder.validation.ValidationMessages.NAME_SIZE;
+
 import jakarta.validation.constraints.Email;
 import jakarta.validation.constraints.Size;
 
 public record UpdateProfileRequest(
-    @Email(message = "Please provide a valid email") String email,
-    @Size(min = 2, max = 50, message = "Name must be between 2 and 50 characters") String name) {}
+    @Email(message = EMAIL_INVALID) String email,
+    @Size(min = NAME_MIN_LENGTH, max = NAME_MAX_LENGTH, message = NAME_SIZE) String name) {}

src/main/java/org/nkcoder/mapper/UserMapper.java

@@ -1,17 +1,25 @@
 package org.nkcoder.mapper;
 
+import java.util.Objects;
+import java.util.Optional;
 import org.nkcoder.dto.user.UserResponse;
 import org.nkcoder.entity.User;
 import org.springframework.stereotype.Component;
 
 @Component
 public class UserMapper {
 
-  public UserResponse toResponse(User user) {
-    if (user == null) {
-      return null;
-    }
+  /** Converts a User entity to UserResponse, returning Optional.empty() is user is null. */
+  public Optional<UserResponse> toResponse(User user) {
+    return Optional.ofNullable(user).map(this::mapToResponse);
+  }
+
+  public UserResponse toResponseOrThrow(User user) {
+    Objects.requireNonNull(user, "User must not be null");
+    return mapToResponse(user);
+  }
 
+  private UserResponse mapToResponse(User user) {
     return new UserResponse(
         user.getId(),
         user.getEmail(),

src/main/java/org/nkcoder/service/AuthService.java

@@ -30,6 +30,12 @@ public class AuthService {
 
   private static final Logger logger = LoggerFactory.getLogger(AuthService.class);
 
+  public static final String USER_ALREADY_EXISTS = "User already exists";
+  public static final String INVALID_CREDENTIALS = "Invalid email or password";
+  public static final String INVALID_REFRESH_TOKEN = "Invalid refresh token";
+  public static final String REFRESH_TOKEN_EXPIRED = "Refresh token expired";
+  public static final String USER_NOT_FOUND = "User not found";
+
   private final UserRepository userRepository;
   private final RefreshTokenRepository refreshTokenRepository;
   private final PasswordEncoder passwordEncoder;
@@ -59,7 +65,7 @@ public AuthResponse register(RegisterRequest request) {
 
     // Check if user already exists
     if (userRepository.existsByEmail(request.email().toLowerCase())) {
-      throw new ValidationException("User already exists");
+      throw new ValidationException(USER_ALREADY_EXISTS);
     }
 
     // Create new user
@@ -81,7 +87,7 @@ public AuthResponse register(RegisterRequest request) {
     // Save refresh token
     saveRefreshToken(tokens.refreshToken(), savedUser.getId(), tokenFamily);
 
-    return new AuthResponse(userMapper.toResponse(savedUser), tokens);
+    return new AuthResponse(userMapper.toResponseOrThrow(savedUser), tokens);
   }
 
   @Transactional
@@ -92,11 +98,11 @@ public AuthResponse login(LoginRequest request) {
     User user =
         userRepository
             .findByEmail(request.email().toLowerCase())
-            .orElseThrow(() -> new AuthenticationException("Invalid email or password"));
+            .orElseThrow(() -> new AuthenticationException(INVALID_CREDENTIALS));
 
     // Check password
     if (!passwordEncoder.matches(request.password(), user.getPassword())) {
-      throw new AuthenticationException("Invalid email or password");
+      throw new AuthenticationException(INVALID_CREDENTIALS);
     }
 
     // Update last login
@@ -110,7 +116,7 @@ public AuthResponse login(LoginRequest request) {
     saveRefreshToken(tokens.refreshToken(), user.getId(), tokenFamily);
 
     logger.debug("User logged in successfully: {}", user.getId());
-    return new AuthResponse(userMapper.toResponse(user), tokens);
+    return new AuthResponse(userMapper.toResponseOrThrow(user), tokens);
   }
 
   @Transactional(isolation = Isolation.SERIALIZABLE)
@@ -127,32 +133,28 @@ public AuthResponse refreshTokens(String refreshToken) {
       RefreshToken storedToken =
           refreshTokenRepository
               .findByTokenForUpdate(refreshToken)
-              .orElseThrow(() -> new AuthenticationException("Invalid refresh token"));
+              .orElseThrow(() -> new AuthenticationException(INVALID_REFRESH_TOKEN));
 
       // Check if token is expired
       if (storedToken.isExpired()) {
         refreshTokenRepository.deleteByToken(refreshToken);
-        throw new AuthenticationException("Refresh token expired");
+        throw new AuthenticationException(REFRESH_TOKEN_EXPIRED);
       }
 
-      // Get user
       User user =
           userRepository
               .findById(userId)
-              .orElseThrow(() -> new AuthenticationException("User not found"));
+              .orElseThrow(() -> new AuthenticationException(USER_NOT_FOUND));
 
-      // Delete old refresh token
       refreshTokenRepository.deleteByToken(refreshToken);
 
       // Generate new tokens with same token family
       AuthTokens tokens = generateAuthTokens(user, tokenFamily);
 
-      // Save new refresh token
       saveRefreshToken(tokens.refreshToken(), user.getId(), tokenFamily);
 
       logger.debug("Tokens refreshed successfully for user: {}", userId);
-      return new AuthResponse(userMapper.toResponse(user), tokens);
-
+      return new AuthResponse(userMapper.toResponseOrThrow(user), tokens);
     } catch (JwtException e) {
       logger.error("Invalid refresh token: {}", e.getMessage());
 
@@ -163,22 +165,23 @@ public AuthResponse refreshTokens(String refreshToken) {
               storedToken ->
                   refreshTokenRepository.deleteByTokenFamily(storedToken.getTokenFamily()));
 
-      throw new AuthenticationException("Invalid refresh token");
+      throw new AuthenticationException(INVALID_REFRESH_TOKEN);
     }
   }
 
   @Transactional
   public void logout(String refreshToken) {
     logger.debug("Logging out user (all devices)");
 
-    // Get token data
-    RefreshToken storedToken = refreshTokenRepository.findByToken(refreshToken).orElse(null);
-    if (storedToken != null) {
-      // Delete entire token family (logout from all devices)
-      refreshTokenRepository.deleteByTokenFamily(storedToken.getTokenFamily());
-      logger.debug(
-          "Logged out from all devices for token family: {}", storedToken.getTokenFamily());
-    }
+    refreshTokenRepository
+        .findByToken(refreshToken)
+        .ifPresent(
+            storedToken -> {
+              // Delete entire token family (logout from all devices)
+              refreshTokenRepository.deleteByTokenFamily(storedToken.getTokenFamily());
+              logger.debug(
+                  "Logged out from all devices for token family: {}", storedToken.getTokenFamily());
+            });
   }
 
   @Transactional