问题
I am quite new to JPA and I am using Apress JPA2 text book to learn it. I was trying to do the first example from the book. This following line of code gives me an error:
TypedQuery query = em.createQuery("SELECT e FROM Employee e", Employee.class);
saying that TypedQuery cannot be resolved to a type. After struggling for sometime I realised that I am using JPA version 1 which does not contain TypedQuery but just Query interface.
My question is whether there is an equivalent statement in JPA version 1. Kindly help. Thanks in advance.
回答1:
As TypedQuery was introduced from JPA-2.0, have to go for Query interface.
1) Native query to map the result type for the query (loosing portability).
Query selectQuery = entityManager.createNativeQuery("SELECT
e FROM Employee e", Employee.class);
2) Creating query & then explicitly casting it to the result type (more preferable).
Query selectQuery = entityManager.createQuery("SELECT e FROM Employee e")
List<Employee> employees = (List<Employee>)selectQuery.getResultList(); //Multiple Result
Employee employee = (Employee)selectQuery.getSingleResult(); //Single Result
来源：https://stackoverflow.com/questions/6119683/typedquery-equivalent-for-jpa-1-0