The old Criteria API has been deprecated and Hibernate prints warnings about this fact. This represents a problem for GORM which is used by thousands of Grails developers world wide and I imagine contributes a reasonable portion to the Hibernate user base.

The reason this represents a problem is there are functional gaps between what is possible with Hibernate Criteria API and what is possible with JPA criteria that we (the GORM team) don't know how to solve to move completely away from Hibernate criteria.

These include:

• An equivalent of Restrictions.sqlRestriction method for custom SQL restrictions
• How define custom criterion (for example for our support for RLIke) https://github.com/grails/gorm-hibernate5/blob/master/grails-datastore-gorm-hibernate5/src/main/groovy/grails/orm/RlikeExpression.java
• No API to do query by example

Apart from that GORM uses the API extensively and it represents a massive task that is maybe impossible to achieve without breaking user applications. The following classes use the API extensively:

• https://github.com/grails/gorm-hibernate5/blob/master/grails-datastore-gorm-hibernate5/src/main/groovy/org/grails/orm/hibernate/query/AbstractHibernateCriteriaBuilder.java
• https://github.com/grails/gorm-hibernate5/blob/master/grails-datastore-gorm-hibernate5/src/main/groovy/org/grails/orm/hibernate/query/AbstractHibernateQuery.java

This issue requests that either the deprecation warnings be removed or that the functional gaps needed for us to completely move away from these APIs are closed so that we can update GORM without breaking existing Grails/GORM applications out there (and there are many).