A group defines a subset of constraints. Instead of validating all constraints for a given object graph, only a subset is validated depending on the group targeted.

Each constraint declaration defines the list of groups it belongs to. If no group is explicitly declared, a constraint belongs to the javax.validation.groups.Default group.

When applying validation, the list of target groups is passed along. If no group is explicitly passed along, the javax.validation.groups.Default group is used.

During cascading, groups can be converted from one to another by the use of javax.validation.groups.ConvertGroup