Create JWT Token - API Controller

JwtTokenController.java

package com.company.controller;

import com.company.model.SuccessResponseModel;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.security.Keys;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import reactor.core.publisher.Mono;

import java.security.Key;
import java.util.Base64;
import java.util.Date;

@RestController
@RequestMapping("/api/v1")
public class JwtTokenController {

    // In plaintext for demo purpose, ALWAYS HAVE THIS ENCRYPTED !!
    private final String base64Secret = "9hgSUF1MeeRfwArdmfn9DHoTYr909raQL5rSUN9EhAZA00oItuPbiY80Gk7QqB37yl9eK4";

    private final long ttl = 30 * 1000L; // 30 seconds

    @GetMapping("/token")
    public Mono<ResponseEntity<SuccessResponseModel>> generateToken() {
        long nowMillis = System.currentTimeMillis();
        Date now = new Date(nowMillis);
        Date expiryDate = new Date(nowMillis + ttl);

        Key key = Keys.hmacShaKeyFor(Base64.getDecoder().decode(base64Secret));

        String jwt = Jwts.builder()
                .header()
                    .add("typ", "JWT")
                    .add("alg", "HS256")
                .and()
                .subject("user")
                .issuedAt(now)
                .expiration(expiryDate)
                .signWith(key)
                .compact();

        SuccessResponseModel responseModel = new SuccessResponseModel();
        responseModel.setToken(jwt);

        return Mono.just(ResponseEntity.ok()).map(e -> ResponseEntity.ok(responseModel));
    }
}