You're getting the error:

Java 8 date/time type java.time.LocalDateTime not supported by default

This happens because Jackson does not support LocalDateTime out of the box. You need to register the JavaTimeModule properly.

Solution

1. Ensure You Have the Correct Dependencies Make sure you have the jackson-datatype-jsr310 dependency in your pom.xml:

<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-jsr310</artifactId>
    <version>2.18.2</version>
</dependency>

2. Register JavaTimeModule in Spring Boot Spring Boot automatically registers JavaTimeModule if the dependency is present. However, in some cases, an explicit configuration is needed.

Create a Jackson configuration class:

@Configuration
public class JacksonConfig {

    @Bean
    public ObjectMapper objectMapper() {
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.registerModule(new JavaTimeModule());
        objectMapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
        return objectMapper;
    }
}

3. Ensure Your ErrorResponse Class Uses @JsonFormat Modify your ErrorResponse class to format LocalDateTime correctly:

@Getter
@Setter
public class ErrorResponse {

    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd'T'HH:mm:ss", timezone = "UTC")
    private LocalDateTime timestamp;
    private int status;
    private String error;
    private String message;
    private String path;

    public ErrorResponse(int status, String error, String message, String path) {
        this.timestamp = LocalDateTime.now();
        this.status = status;
        this.error = error;
        this.message = message;
        this.path = path;
    }
}

4. Modify Your Authentication Entry Point Update your AuthenticationEntryPointJwt to use ObjectMapper properly:

@Component
public class AuthenticationEntryPointJwt implements AuthenticationEntryPoint {

    private final ObjectMapper objectMapper;

    @Autowired
    public AuthenticationEntryPointJwt(ObjectMapper objectMapper) {
        this.objectMapper = objectMapper;
    }

    @Override
    public void commence(HttpServletRequest request, HttpServletResponse response, AuthenticationException authException) throws IOException {
        response.setContentType(MediaType.APPLICATION_JSON_VALUE);
        response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);

        ErrorResponse errorResponse = new ErrorResponse(
                HttpServletResponse.SC_FORBIDDEN,
                "Forbidden",
                "You do not have permission to access this resource.",
                request.getRequestURI()
        );

        // Convert ErrorResponse to JSON
        response.getWriter().write(objectMapper.writeValueAsString(errorResponse));
    }
}