JWT Authentication Filter

JwtAuthenticationFilter.java

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.http.HttpHeaders;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.util.StringUtils;
import org.springframework.web.filter.OncePerRequestFilter;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class JwtAuthenticationFilter extends OncePerRequestFilter {

    @Value("${jwt.secret}")
    private String jwtSecret;

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        try {
            String jwt = getJwtFromRequest(request);

            if (StringUtils.hasText(jwt) && validateToken(jwt)) {
                Claims claims = Jwts.parser()
                        .setSigningKey(jwtSecret)
                        .parseClaimsJws(jwt)
                        .getBody();

                String username = claims.getSubject();

                // You can do further validation or processing here

                UsernamePasswordAuthenticationToken authentication = new UsernamePasswordAuthenticationToken(username, null, null);
                SecurityContextHolder.getContext().setAuthentication(authentication);
            }
        } catch (Exception ex) {
            // Handle exception if token is invalid
        }

        filterChain.doFilter(request, response);
    }

    private String getJwtFromRequest(HttpServletRequest request) {
        String bearerToken = request.getHeader(HttpHeaders.AUTHORIZATION);

        if (StringUtils.hasText(bearerToken) && bearerToken.startsWith("Bearer ")) {
            return bearerToken.substring(7);
        }

        return null;
    }

    private boolean validateToken(String jwt) {
        // Implement your validation logic here
        // For example, you can check token expiration, signature validity, etc.
        return true;
    }
}