How to get field Name in default message in custom annotation?

I have created custom annotation to check not null value for my model class attribute in my REST API project.

@Documented
@Target({ ElementType.PARAMETER, ElementType.FIELD, ElementType.METHOD, ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
@ReportAsSingleViolation
@Constraint(validatedBy = CheckNotNull.NotNullValidator.class)
public @interface CheckNotNull {

    String value() default "";

    String message() default "{value} can not be null or empty ";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

    class NotNullValidator implements ConstraintValidator<CheckNotNull, String> {

        @Override
        public void initialize(CheckNotNull constraintAnnotation) {
        }

        @Override
        public boolean isValid(String value, ConstraintValidatorContext context) {
            return "null".equalsIgnoreCase(value) ? true : value == null ? true : value.trim().equals("") ? true :false;
        }

    }
}

However, if I used this annotation on attribute.
ex:

@CheckNotNull(value = "UserName")
private String login

I have another class where ConstraintViloationException is captured. With @NotNull annotation it is perfectly working.

public final class ValidationExceptionMapper implements ExceptionMapper<ValidationException> {

    @Override
    public Response toResponse(final ValidationException exception) {
        RestError error = new RestError();
        
        if (exception instanceof ConstraintViolationException) {
            error.setHttpStatusCode(Response.Status.BAD_REQUEST.getStatusCode());
            error.setCode(ErrorCodes.ERR_INVALID_INPUT);

            final ConstraintViolationException cve = (ConstraintViolationException) exception;
            
            StringBuilder msgBuilder = new StringBuilder("Following constraint violations have been detected: ");
            for(ConstraintViolation<?> violation: cve.getConstraintViolations()) {
                    msgBuilder.append(StringEscapeUtils.escapeHtml(violation.getMessage()));
            }
            error.setMessage(msgBuilder.toString());
        }
        return Response.status(error.getHttpStatusCode())
                .entity(error)
                .type(MediaType.APPLICATION_JSON)
                .build();   
    }
}

My logic is not working with applying custom annotation. Any issue with my custom annotation?

Any inputs are most welcome. Thank you.

You need to pass that attribute with field whatever you had declared as any dynamic message {value} ;

In your case you need pass that as @CheckNotNull(value="name").

@CheckNotNull(value="name")
private String firstName;

@CheckNotNull(value="UserName")
private String name;

This will help you.

I have overridden ValidationMessages.properties file.

javax.validation.constraints.NotNull.message  = {0} cannot be null or empty.
org.hibernate.validator.constraints.NotBlank.message  = {0} cannot be null or empty
org.hibernate.validator.constraints.NotEmpty.message  = {0} cannot be null or empty

And then, In my response class

public Response toResponse(final ValidationException exception) {
        RestError error = new RestError();
        StringBuilder errorPath = new StringBuilder();
        if (exception instanceof ConstraintViolationException) {
            error.setHttpStatusCode(Response.Status.BAD_REQUEST.getStatusCode());

            final ConstraintViolationException cve = (ConstraintViolationException) exception;
            
            StringBuilder msgBuilder = new StringBuilder("Following constraint violations have been detected: ");
            for(ConstraintViolation<?> violation: cve.getConstraintViolations()) {
                Class<?> annotationType = violation.getConstraintDescriptor().getAnnotation().annotationType();

               if (annotationType == NotEmpty.class || annotationType == NotNull.class
                        || annotationType == NotBlank.class) {
                    msgBuilder = getErrorMessage(violation, msgBuilder);
                }
                else {
                    msgBuilder.append(StringEscapeUtils.escapeHtml(violation.getMessage()));
                }
                errorPath.append(" path: ").append(violation.getPropertyPath().toString());
                
               
            }
            error.setMessage(msgBuilder.toString());
        } 
        return Response.status(error.getHttpStatusCode())
                .entity(error)
                .type(MediaType.APPLICATION_JSON)
                .build();   
    }

And I have written separate method for getErrorMessage

private StringBuilder getErrorMessage(ConstraintViolation<?> violation, StringBuilder msgBuilder) {
        // For default error message
        if (violation.getMessage().contains("{0}")) {
            String[] splitPath =  violation.getPropertyPath().toString().split("[.]");
            String fieldName = splitPath[splitPath.length - 1];
            String messageWithFieldName = MessageFormat.format(violation.getMessage(), fieldName);
            msgBuilder.append((messageWithFieldName)).append(";");
        } else {
            // For customized error message
            msgBuilder.append(violation.getMessage()).append(";");
        }
        return msgBuilder;
    }

so if their is no custom message for @NotNull, @NotEmpty and @NotBlank annotation, then replace placeholder in default message with field name which is extracted from the path in order to have user-friendly error message.
examples:

@NotNull
private String name;

message: "Following constraint violations have been detected: name cannot be null or empty"


@NotNull(message = "UserName can not be null")
private String name;

message: "Following constraint violations have been detected: UserName can not be null"


@NotNull
@JsonProperty("username")
private String name;

message: "Following constraint violations have been detected: name cannot be null or empty"