I am in the process of plugging the hibernate validator into our application, but I was surprised to find that in order to make it work I will have to add the new @NotNull and @Length annotations. Our application already uses the @Column(name="foo", length=X, nullable=false) annotation so why can't the validator just read the @Column annotations instead of looking for new ones?

I envision it being done the other way around, ie having JPA reading the metadata form validator.

Interesting.

I think my original post was a little blunt :)

My project already uses JPA and Hibernate annotations, so we already have the @Column annotations with nullability and length set on them. These parameters are used to generate the DDL, which works just brilliantly. Now we want to add validation to the app and it seems that validation needs a whole new set of annotations?

I guess what I am asking is, what is the difference, both in terms of what the hibernate tools sees, and what hibernate runtime sees between the following declarations:

@Column(name="Foo", length=20, nullability=false)
private String name;

and

@Column(name="Foo")
@Length(max=20)
@NotNull
private String name;

I prefer the terseness of the former declaration, but the Hibernate Validator doesn't appear to look at the @Column annotation to derive max length and nullability information.

Also, what would be the result if conflicting parameters were set?

i.e.

@Column(name="Foo", length=20, nullability=true)
@Length(max=40)
@NotNull

Would the hibernate toolset only read the column annotation to generate the DDL, and leave the Validator to use the Length and NotNull annotations, or would the presence of a Length annotation trump the length parameter in the Column annotation?

For the first example, there is no difference

I don't want to infer a global object level constraint from a DB specific annotation.

If you have conflicting annotations, that's not really defined, but the current implementation will use the validation annotations in priority

More informations at:
http://opensource.atlassian.com/projects/hibernate/browse/HV-43

Regards,
Leonardo