How can user login functionality be implemented using S…

To implement user login functionality using SpringBoot and JWT, you can follow these steps:

1. The pom.xml file

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-security</artifactId>
</dependency>

<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt</artifactId>
    <version>0.9.1</version>
</dependency>

1. Create user entity: Develop a user object class that includes attributes such as username and password.

public class User {
    private String username;
    private String password;

    // getter and setter
}

1. Service for managing user details

@Service
public class UserDetailsServiceImpl implements UserDetailsService {

    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        // 从数据库或其他数据源加载用户信息
        User user = userRepository.findByUsername(username);
        if (user == null) {
            throw new UsernameNotFoundException("User not found");
        }
        return new org.springframework.security.core.userdetails.User(user.getUsername(), user.getPassword(), new ArrayList<>());
    }
}

1. Create a login controller: Develop a login controller class to handle user login requests.

@RestController
public class LoginController {

    @Autowired
    private AuthenticationManager authenticationManager;
    @Autowired
    private JwtUtils jwtUtils;

    @PostMapping("/login")
    public ResponseEntity<?> login(@RequestBody User user) {
        try {
            authenticationManager.authenticate(new UsernamePasswordAuthenticationToken(user.getUsername(), user.getPassword()));
            String token = jwtUtils.generateToken(user.getUsername());
            return ResponseEntity.ok(token);
        } catch (Exception e) {
            return ResponseEntity.status(HttpStatus.UNAUTHORIZED).build();
        }
    }
}

1. Create a JWT utility class: Implement a utility class for creating and parsing JSON Web Tokens.

@Component
public class JwtUtils {

    private final String secret = "your-secret-key";
    private final long expiration = 86400000;

    public String generateToken(String username) {
        Date now = new Date();
        Date expiryDate = new Date(now.getTime() + expiration);

        return Jwts.builder()
                .setSubject(username)
                .setIssuedAt(now)
                .setExpiration(expiryDate)
                .signWith(SignatureAlgorithm.HS512, secret)
                .compact();
    }

    public String getUsernameFromToken(String token) {
        return Jwts.parser()
                .setSigningKey(secret)
                .parseClaimsJws(token)
                .getBody()
                .getSubject();
    }

    public boolean isTokenValid(String token, UserDetails userDetails) {
        String username = getUsernameFromToken(token);
        return (username.equals(userDetails.getUsername()) && !isTokenExpired(token));
    }

    private boolean isTokenExpired(String token) {
        Date expirationDate = Jwts.parser()
                .setSigningKey(secret)
                .parseClaimsJws(token)
                .getBody()
                .getExpiration();
        return expirationDate.before(new Date());
    }
}

1. properties file for application

spring.security.user.name=admin
spring.security.user.password=admin
spring.security.user.roles=USER,ADMIN

1. Set up a JWT filter: Create a JWT filter class to validate the JWT in the request and authenticate the information in the Security context.

@Component
public class JwtTokenFilter extends OncePerRequestFilter {

    @Autowired
    private JwtUtils jwtUtils;
    @Autowired
    private UserDetailsServiceImpl userDetailsService;

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        String header = request.getHeader("Authorization");

        if (StringUtils.hasText(header) && header.startsWith("Bearer ")) {
            String token = header.substring(7);
            String username = jwtUtils.getUsernameFromToken(token);

            if (StringUtils.hasText(username) && SecurityContextHolder.getContext().getAuthentication() == null) {
                UserDetails userDetails = userDetailsService.loadUserByUsername(username);

                if (jwtUtils.isTokenValid(token, userDetails)) {
                    UsernamePasswordAuthenticationToken authenticationToken = new UsernamePasswordAuthenticationToken(userDetails, null, userDetails.getAuthorities());
                    authenticationToken.setDetails(new WebAuthenticationDetailsSource().buildDetails(request));
                    SecurityContextHolder.getContext().setAuthentication(authenticationToken);
                }
            }
        }

        filterChain.doFilter(request, response);
    }
}

1. Set up Spring Security