Initialize Spring Boot backend with JWT auth

src/main/java/com/openisle/OpenIsleApplication.java

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+package com.openisle;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class OpenIsleApplication {
+    public static void main(String[] args) {
+        SpringApplication.run(OpenIsleApplication.class, args);
+    }
+}

src/main/java/com/openisle/config/SecurityConfig.java

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+package com.openisle.config;
+
+import com.openisle.service.JwtService;
+import com.openisle.repository.UserRepository;
+import lombok.RequiredArgsConstructor;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.HttpMethod;
+import org.springframework.security.authentication.AuthenticationManager;
+import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
+import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.config.http.SessionCreationPolicy;
+import org.springframework.security.core.userdetails.UserDetails;
+import org.springframework.security.core.userdetails.UserDetailsService;
+import org.springframework.security.core.userdetails.UsernameNotFoundException;
+import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
+import org.springframework.security.web.SecurityFilterChain;
+import org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter;
+import org.springframework.web.filter.OncePerRequestFilter;
+
+import jakarta.servlet.FilterChain;
+import jakarta.servlet.ServletException;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+@Configuration
+@RequiredArgsConstructor
+public class SecurityConfig {
+    private final JwtService jwtService;
+    private final UserRepository userRepository;
+
+    @Bean
+    public PasswordEncoder passwordEncoder() {
+        return new BCryptPasswordEncoder();
+    }
+
+    @Bean
+    public UserDetailsService userDetailsService() {
+        return username -> userRepository.findByUsername(username)
+                .<UserDetails>map(user -> org.springframework.security.core.userdetails.User
+                        .withUsername(user.getUsername())
+                        .password(user.getPassword())
+                        .authorities("USER")
+                        .build())
+                .orElseThrow(() -> new UsernameNotFoundException("User not found"));
+    }
+
+    @Bean
+    public AuthenticationManager authenticationManager(HttpSecurity http, PasswordEncoder passwordEncoder, UserDetailsService userDetailsService) throws Exception {
+        return http.getSharedObject(AuthenticationManagerBuilder.class)
+                .userDetailsService(userDetailsService)
+                .passwordEncoder(passwordEncoder)
+                .and()
+                .build();
+    }
+
+    @Bean
+    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
+        http.csrf(csrf -> csrf.disable())
+            .sessionManagement(sm -> sm.sessionCreationPolicy(SessionCreationPolicy.STATELESS))
+            .authorizeHttpRequests(auth -> auth
+                    .requestMatchers(HttpMethod.POST, "/api/auth/**").permitAll()
+                    .anyRequest().authenticated()
+            )
+            .addFilterBefore(jwtAuthenticationFilter(), UsernamePasswordAuthenticationFilter.class);
+        return http.build();
+    }
+
+    @Bean
+    public OncePerRequestFilter jwtAuthenticationFilter() {
+        return new OncePerRequestFilter() {
+            @Override
+            protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
+                String authHeader = request.getHeader("Authorization");
+                if (authHeader != null && authHeader.startsWith("Bearer ")) {
+                    String token = authHeader.substring(7);
+                    try {
+                        String username = jwtService.validateAndGetSubject(token);
+                        UserDetails userDetails = userDetailsService().loadUserByUsername(username);
+                        UsernamePasswordAuthenticationToken authToken = new UsernamePasswordAuthenticationToken(userDetails, null, userDetails.getAuthorities());
+                        org.springframework.security.core.context.SecurityContextHolder.getContext().setAuthentication(authToken);
+                    } catch (Exception ignored) {
+                    }
+                }
+                filterChain.doFilter(request, response);
+            }
+        };
+    }
+}

src/main/java/com/openisle/controller/AuthController.java

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+package com.openisle.controller;
+
+import com.openisle.model.User;
+import com.openisle.service.EmailService;
+import com.openisle.service.JwtService;
+import com.openisle.service.UserService;
+import lombok.Data;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+@RestController
+@RequestMapping("/api/auth")
+@RequiredArgsConstructor
+public class AuthController {
+    private final UserService userService;
+    private final JwtService jwtService;
+    private final EmailService emailService;
+
+    @PostMapping("/register")
+    public ResponseEntity<?> register(@RequestBody RegisterRequest req) {
+        User user = userService.register(req.getUsername(), req.getEmail(), req.getPassword());
+        emailService.sendEmail(user.getEmail(), "Welcome to OpenIsle", "Thank you for registering.");
+        String token = jwtService.generateToken(user.getUsername());
+        return ResponseEntity.ok(new JwtResponse(token));
+    }
+
+    @PostMapping("/login")
+    public ResponseEntity<?> login(@RequestBody LoginRequest req) {
+        return userService.authenticate(req.getUsername(), req.getPassword())
+                .map(user -> ResponseEntity.ok(new JwtResponse(jwtService.generateToken(user.getUsername()))))
+                .orElse(ResponseEntity.status(401).build());
+    }
+
+    @Data
+    private static class RegisterRequest {
+        private String username;
+        private String email;
+        private String password;
+    }
+
+    @Data
+    private static class LoginRequest {
+        private String username;
+        private String password;
+    }
+
+    @Data
+    private static class JwtResponse {
+        private final String token;
+    }
+}

src/main/java/com/openisle/controller/HelloController.java

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+package com.openisle.controller;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class HelloController {
+    @GetMapping("/api/hello")
+    public String hello() {
+        return "Hello, Authenticated User";
+    }
+}

src/main/java/com/openisle/model/User.java

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+package com.openisle.model;
+
+import jakarta.persistence.*;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+@Entity
+@Getter
+@Setter
+@NoArgsConstructor
+@Table(name = "users")
+public class User {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(nullable = false, unique = true)
+    private String username;
+
+    @Column(nullable = false, unique = true)
+    private String email;
+
+    @Column(nullable = false)
+    private String password;
+}

src/main/java/com/openisle/repository/UserRepository.java

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+package com.openisle.repository;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+import com.openisle.model.User;
+import java.util.Optional;
+
+public interface UserRepository extends JpaRepository<User, Long> {
+    Optional<User> findByUsername(String username);
+    Optional<User> findByEmail(String email);
+}

src/main/java/com/openisle/service/EmailService.java

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+package com.openisle.service;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.http.HttpEntity;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.MediaType;
+import org.springframework.stereotype.Service;
+import org.springframework.web.client.RestTemplate;
+
+import java.util.HashMap;
+import java.util.Map;
+
+@Service
+public class EmailService {
+
+    @Value("${resend.api.key}")
+    private String apiKey;
+
+    private final RestTemplate restTemplate = new RestTemplate();
+
+    public void sendEmail(String to, String subject, String text) {
+        String url = "https://api.resend.com/emails"; // hypothetical endpoint
+
+        HttpHeaders headers = new HttpHeaders();
+        headers.setContentType(MediaType.APPLICATION_JSON);
+        headers.set("Authorization", "Bearer " + apiKey);
+
+        Map<String, String> body = new HashMap<>();
+        body.put("to", to);
+        body.put("subject", subject);
+        body.put("text", text);
+        body.put("from", "demo@openisle.example");
+
+        HttpEntity<Map<String, String>> entity = new HttpEntity<>(body, headers);
+        restTemplate.exchange(url, HttpMethod.POST, entity, String.class);
+    }
+}

src/main/java/com/openisle/service/JwtService.java

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+package com.openisle.service;
+
+import io.jsonwebtoken.Claims;
+import io.jsonwebtoken.Jwts;
+import io.jsonwebtoken.SignatureAlgorithm;
+import io.jsonwebtoken.security.Keys;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Service;
+
+import java.security.Key;
+import java.util.Date;
+
+@Service
+public class JwtService {
+
+    @Value("${app.jwt.secret}")
+    private String secret;
+
+    @Value("${app.jwt.expiration}")
+    private long expiration;
+
+    private Key getSigningKey() {
+        return Keys.hmacShaKeyFor(secret.getBytes());
+    }
+
+    public String generateToken(String subject) {
+        Date now = new Date();
+        Date expiryDate = new Date(now.getTime() + expiration);
+        return Jwts.builder()
+                .setSubject(subject)
+                .setIssuedAt(now)
+                .setExpiration(expiryDate)
+                .signWith(getSigningKey(), SignatureAlgorithm.HS256)
+                .compact();
+    }
+
+    public String validateAndGetSubject(String token) {
+        Claims claims = Jwts.parserBuilder()
+                .setSigningKey(getSigningKey())
+                .build()
+                .parseClaimsJws(token)
+                .getBody();
+        return claims.getSubject();
+    }
+}

src/main/java/com/openisle/service/UserService.java

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+package com.openisle.service;
+
+import com.openisle.model.User;
+import com.openisle.repository.UserRepository;
+import lombok.RequiredArgsConstructor;
+import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
+import org.springframework.stereotype.Service;
+
+import java.util.Optional;
+
+@Service
+@RequiredArgsConstructor
+public class UserService {
+    private final UserRepository userRepository;
+    private final PasswordEncoder passwordEncoder = new BCryptPasswordEncoder();
+
+    public User register(String username, String email, String password) {
+        if (userRepository.findByUsername(username).isPresent() || userRepository.findByEmail(email).isPresent()) {
+            throw new RuntimeException("User already exists");
+        }
+        User user = new User();
+        user.setUsername(username);
+        user.setEmail(email);
+        user.setPassword(passwordEncoder.encode(password));
+        return userRepository.save(user);
+    }
+
+    public Optional<User> authenticate(String username, String password) {
+        return userRepository.findByUsername(username)
+                .filter(user -> passwordEncoder.matches(password, user.getPassword()));
+    }
+}