No data type for node: org.hibernate.hql.internal.ast.tree.IdentNode HQL

It occurs sometimes when keyword 'new' is missed for your DTO (DATA TRANSFER OBJECT).

SQL queries use column names while HQL queries use Class properties. You're selecting artifact_id from Classification but the Classification class has no property named 'artifact_id'. To fix it, use the class property in your HQL.

SELECT artifactId FROM Classification