Validate image if existing or not null only in spring boot? - spring-boot

Question

I'm trying to validate image in Spring boot with a custom messages and custom validator.
Here is my file path for the validator files
I just need to know how to check first if the image file is existing or not null and then validate it.
I need to mention that my image can be null value, in this case, I should not do the validation.
Here is the example for more clarification:
I first created the annotation as follows:
import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
#Target(ElementType.FIELD)
#Retention(RetentionPolicy.RUNTIME)
#Constraint(validatedBy = {ImageFileValidator.class})
public #interface ValidImage {
String message() default "Invalid image file";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
I've created the validator as following:
import org.springframework.web.multipart.MultipartFile;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
public class ImageFileValidator implements ConstraintValidator<ValidImage, MultipartFile> {
#Override
public void initialize(ValidImage constraintAnnotation) {
}
#Override
public boolean isValid(MultipartFile multipartFile, ConstraintValidatorContext context) {
boolean result = true;
String contentType = multipartFile.getContentType();
if (!isSupportedContentType(contentType)) {
context.disableDefaultConstraintViolation();
context.buildConstraintViolationWithTemplate(
"Only PNG or JPG images are allowed.")
.addConstraintViolation();
result = false;
}
return result;
}
private boolean isSupportedContentType(String contentType) {
return contentType.equals("image/png")
|| contentType.equals("image/jpg")
|| contentType.equals("image/jpeg");
}
}
Finally, applied the annotation as following:
public class CreateUserParameters {
#ValidImage
private MultipartFile image;
...
}
The code of the custom validator was here :
File upload in Spring Boot: Uploading, validation, and exception handling
by Wim Deblauwe in the last comment.

Answer 1

This is not really the answer for my question, but a temporary solution if someone has the same issue.
So the thing is, If the image is null, I will just tell the ImageFileValidator to send True to ValidImage and then the image will be validated.
Which means I don't have to send errors.
#Override
public boolean isValid(MultipartFile multipartFile, ConstraintValidatorContext context) {
boolean result = true;
String contentType = "";
try {
contentType = multipartFile.getContentType();
if(fileNameLength(multipartFile) == 0) {
return result;
}
} catch(NullPointerException e) {
e.printStackTrace();
}
if (!isSupportedContentType(contentType)) {
.....
The rest of the code can be found above. It might return NullException as well, so make sure to handle it.