等同于JPA 1.0的TypedQuery [英] TypedQuery equivalent for JPA 1.0

问题描述

我对JPA还是很陌生，我正在使用Apress JPA2教科书来学习它.我试图做这本书的第一个例子.以下代码行给我一个错误:

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(从员工e的SELECT e"，Employee.class);

TypedQuery query = em.createQuery("SELECT e FROM Employee e", Employee.class);

表示无法将TypedQuery解析为一种类型.经过一段时间的努力，我意识到我正在使用JPA版本1，该版本不包含TypedQuery而是仅包含Query接口.

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.

我的问题是JPA版本1中是否存在等效的声明.请帮助.预先感谢.

My question is whether there is an equivalent statement in JPA version 1. Kindly help. Thanks in advance.

推荐答案

由于TypedQuery是从JPA-2.0引入的，因此必须使用Query接口.

As TypedQuery was introduced from JPA-2.0, have to go for Query interface.

1)本机查询，以映射查询的结果类型(失去可移植性).

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)创建查询&然后将其显式转换为结果类型(更可取).

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

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