@AttributeOverrides({
    @AttributeOverride(name="name",    column=@Column(name="attachment_name")),
    @AttributeOverride(name="mimeType",column=@Column(name="attachment_mimeType")),
    @AttributeOverride(name="bytes",   column=@Column(name="attachment_bytes"))
})
@Embedded
private BlobJpaEmbeddable attachment;

@Property()
@PropertyLayout()
public Blob getPdf() {
  return BlobJpaEmbeddable.toBlob(pdf);
}
public void setPdf(final Blob pdf) {
  this.pdf = BlobJpaEmbeddable.fromBlob(pdf);
}