import javax.validation.constraints.Email;
import javax.validation.constraints.Pattern;

public class User {

    @Email
    private String email;

    @Pattern(regexp = "^[0-9] $")
    private String phoneNumber;
}

String sanitizedInput = request.getParameter("input");
sanitizedInput = htmlEncoder.encode(sanitizedInput);

String query = "SELECT * FROM users WHERE username = ?";
PreparedStatement statement = connection.prepareStatement(query);
statement.setString(1, username);
ResultSet results = statement.executeQuery();

@Configuration
public class CorsConfig {

    @Bean
    public CorsFilter corsFilter() {
        CorsConfiguration corsConfiguration = new CorsConfiguration();
        corsConfiguration.setAllowedOrigins(Arrays.asList("https://example.com"));
        corsConfiguration.setAllowedHeaders(Arrays.asList("*"));
        corsConfiguration.setAllowedMethods(Arrays.asList("GET", "POST", "PUT", "DELETE"));
        corsConfiguration.setMaxAge(3600L);
        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
        source.registerCorsConfiguration("/**", corsConfiguration);
        return new CorsFilter(source);
    }
}

import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;

public class TokenAuthentication {

    public static String generateToken(String username) {
        String secretKey = "my-secret-key";
        return Jwts.builder()
                .setSubject(username)
                .signWith(SignatureAlgorithm.HS512, secretKey)
                .compact();
    }

    public static String parseToken(String token) {
        String secretKey = "my-secret-key";
        return Jwts.parser()
                .setSigningKey(secretKey)
                .parseClaimsJws(token)
                .getBody()
                .getSubject();
    }
}