我如何验证某人是否已上传文件

Question

I am getting this error message.

javax.validation.UnexpectedTypeException: HV000030: No validator could be found for type: byte[].

The code is

@NotBlank(message = DocumentForm.NOT_BLANK_MESSAGE)
private byte[] file;

How can i do a validate if a person has uploaded a file

Answer 1

I don't know what annotations are available for a byte array, if any. However, you could implement your own validator without much trouble.

Something like:

public class ModelWithFileFieldValidator implements Validator {

    public boolean supports(Class clazz) {
        return ModelWithFileField.class.equals(clazz);
    }

    public void validate(Object obj, Errors e) {
        byte[] field = ((ModelWithFileField)obj).getBytes();
        if (field == null || field.length == 0) {
            e.rejectValue("file", "empty");
        }
    }
}

Answer 2

@NotBlank is for Strings. It's also not part of the standard for that matter. You probably want to go with @NotNull . It only checks if a file is there, though, not if it's empty. If that's necessary as well you can use @Size(min = 1) .