On 01/12/2015 05:51 AM, Chris Hegarty wrote:
On 08/01/15 22:03, David M. Lloyd wrote:
....
private static void validate(GetField fields) {
if (fields.getInt("lo") > fields.getInt("hi")) { ... }
}
...
In fact you cannot validate invariants across multiple objects at all
using this method *or* readObject() (existing or enhanced) unless the
object in question is an enum, Class, or String (and a few other special
cases) because you can't rely on initialization order during
deserialization. That's the very reason why OIS#registerValidation()
even exists - inter-object validation is not possible until after the
root-most readObject has completed, which is the time when validations
are executed. Robust validation of a given object class may require two
stages - "near" validation and "spanning" validation - to fully
validate. However the readObject() approach and its proposed variations
(including the static validate() version) can still be useful for
fail-fast and non-complex validations; you just have to understand that
(just as today) any Object you examine might not be fully initialized
yet.
If I may, I'd like to build a little on this proposal:
1) Specify that validate is called down the hierarchy, from
j.l.Object.
2) Provide access to persistent supertype's fields, so they can
participate in the validation.
public static abstract class GetField {
....
/**
* Returns the persistent fields of the supertype, read from
* the stream, or null if the the supertype is not Serializable.
*/
public abstract GetField superTypeFields();
}
Maybe limited to accessible fields?
--
- DML
