Steve Ebersole The ParameterizedType}}is called after the Type is constructed, and, in my case, I need to change the {{MutableMutabilityPlan which can only be done at Type instantiating time, as that’s how the org.hibernate.type.descriptor.java.AbstractTypeDescriptor allows configuring the mutabilityPlan, which is a final variable.

For more context, check out this issue I bumped into when creating JSON Hibernate Types that required custom Jackson ObjectMappers.