JPQL Constructor Expression – org.hibernate.hql.ast.QuerySyntaxException:Table is not mapped

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according to the book “Pro EJB 3 Java Persistence API”

Constructor Expressions

A more powerful form of SELECT clause involving multiple expressions is the constructor
expression, which specifies that the results of the query are to be stored using a user-specified
object type. Consider the following query:

SELECT NEW example.EmployeeDetails(e.name, e.salary, e.department.name)
FROM Employee e

The result type of this query is the type example.EmployeeDetails. As the query processor
iterates over the results of the query, it instantiates new instances of EmployeeDetails using the
constructor that matches the expression types listed in the query. In this case the expression
types are String, Double, and String, so the query engine will search for a constructor with those
class types for arguments. Each row in the resulting query collection is therefore an instance of
EmployeeDetails containing the employee name, salary, and department name.

The result object type must be referred to using the fully qualified name of the object. The
class does not have to be mapped to the database in any way, however. Any class with a constructor
compatible with the expressions listed in the SELECT clause can be used in a constructor
expression.

Constructor expressions are powerful tools for constructing coarse-grained data transfer
objects or view objects for use in other application tiers. Instead of manually constructing
these objects, a single query can be used to gather together view objects ready for presentation
on a web page.

The example code is as follows

List result = em.createQuery("SELECT NEW example.EmpMenu(e.name, e.department.name) " +
         "FROM Project p JOIN p.employees e " +
         "WHERE p.name = ?1 " +
        "ORDER BY e.name").setParameter(1, projectName).getResultList();

The EmpMenu class is a simple pojo, no annotations but has the correct constructor to match the constructor expression. The result is a List of EmpMenu objects for each row returned.

I believe the part of your SQL “…. From Schema1.TableA ms ..” should refer to an entity that is mapped. So you should have an entity mapped to TableA, and then the jpql should be something more along the lines of “…. From MyTableAEntity ms …” where MyTableAEntity has all the proper jpa annotations mapping it to DB table TableA. As the book snippet states, the target of “SELECT NEW …” does not have to be mapped, but the entity referred to in the FROM clause does.

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