JFace Data Binding/Validators
Validators are used to validate values in various stages of the binding pipeline (before conversion, after conversion, and just before setting the value). A validator is an implementation of the IValidator interface which for a given value produces a validation status of type IStatus. Bindings use two validators, one for each direction (model to target and target to model). It is recommended (but not required) that you use the static methods on ValidationStatus to create status objects returned from IValidator.validate().
Currently, there is no public API for standard validators because simple validators are trivial to write, and more complex ones tend to be highly application-specific. We do however recommend that in your projects, you build your own library of validators for application-internal reuse.
Validation in the context of bindings can only look at one value at a time. For cross-field validation involving more than one value, you can use the helper class MultiValidator.