Implement login with DTO and secure password validation

src/main/java/org/example/alfs/config/PasswordConfig.java

@@ -0,0 +1,16 @@
+package org.example.alfs.config;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
+
+@Configuration
+public class PasswordConfig {
+
+    // Makes password encoder available in the whole app
+    @Bean
+    public PasswordEncoder passwordEncoder(){
+        return new BCryptPasswordEncoder();
+    }
+}

src/main/java/org/example/alfs/controllers/AuthController.java

@@ -0,0 +1,39 @@
+package org.example.alfs.controllers;
+
+import org.example.alfs.dto.auth.LoginRequestDTO;
+import org.example.alfs.dto.auth.LoginResponseDTO;
+import org.example.alfs.entities.User;
+import org.example.alfs.services.AuthService;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+import jakarta.validation.Valid;
+
+@RestController
+@RequestMapping("/auth")
+public class AuthController {
+
+    private final AuthService authService;
+
+    public AuthController(AuthService authService) {
+        this.authService = authService;
+    }
+
+    /**
+     * Handles user login by validating credentials and returning user details.
+     */
+    @PostMapping("/login")
+    public LoginResponseDTO login(@Valid @RequestBody LoginRequestDTO request) {
+
+        User user = authService.login(
+                request.getUsername(),
+                request.getPassword()
+        );
+
+        return new LoginResponseDTO(
+                user.getUsername(),
+                user.getRole().name()
+        );
+    }
+}

src/main/java/org/example/alfs/dto/auth/LoginRequestDTO.java

@@ -0,0 +1,17 @@
+package org.example.alfs.dto.auth;
+
+import jakarta.validation.constraints.NotBlank;
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+public class LoginRequestDTO {
+
+    @NotBlank(message = "Username is required")
+    private String username;
+
+    @NotBlank(message = "Password is required")
+    private String password;
+
+}

src/main/java/org/example/alfs/dto/auth/LoginResponseDTO.java

@@ -0,0 +1,12 @@
+package org.example.alfs.dto.auth;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@Getter
+@AllArgsConstructor
+public class LoginResponseDTO {
+
+    private String username;
+    private String role;
+}

src/main/java/org/example/alfs/entities/User.java

@@ -27,6 +27,14 @@ public class User {
     private String passwordHash;
 
     @Enumerated(EnumType.STRING)
+    @Column(nullable = false)
     private Role role;
 
+    @PrePersist
+    public void prePersist() {
+        if (role == null) {
+            role = Role.REPORTER;
+        }
+    }
+
 }

src/main/java/org/example/alfs/repositories/UserRepository.java

@@ -7,4 +7,5 @@
 
 public interface UserRepository extends JpaRepository<User, Long> {
 
+    Optional<User> findByUsername(String username);
 }

src/main/java/org/example/alfs/services/AuthService.java

@@ -0,0 +1,40 @@
+package org.example.alfs.services;
+
+import org.example.alfs.entities.User;
+import org.example.alfs.repositories.UserRepository;
+import org.springframework.http.HttpStatus;
+import org.springframework.security.crypto.password.PasswordEncoder;
+import org.springframework.stereotype.Service;
+import org.springframework.web.server.ResponseStatusException;
+
+@Service
+public class AuthService {
+
+    private final PasswordEncoder passwordEncoder;
+    private final UserRepository userRepository;
+
+    public AuthService(PasswordEncoder passwordEncoder, UserRepository userRepository) {
+        this.passwordEncoder = passwordEncoder;
+        this.userRepository = userRepository;
+    }
+
+    /**
+     * Authenticates a user by verifying username and password.
+     */
+    public User login(String username, String password) {
+
+        User user = userRepository.findByUsername(username)
+                .orElseThrow(() -> new ResponseStatusException(
+                        HttpStatus.UNAUTHORIZED,
+                        "Invalid username or password"
+                ));
+        if (!passwordEncoder.matches(password, user.getPasswordHash())) {
+            throw new ResponseStatusException(
+                    HttpStatus.UNAUTHORIZED,
+                    "Invalid username or password"
+            );
+        }
+
+        return user;
+    }
+}