JPA复合主键表未返回值

Question

我是新的JPA，当我从复合主键表中检索值时遇到了异常。

异常说明：

Problem compiling [select t from ASSIGN_TASK_EMPLOYEE t]. 
    [14, 34] The abstract schema type 'ASSIGN_TASK_EMPLOYEE' is unknown.
        at org.eclipse.persistence.internal.jpa.EntityManagerImpl.createQuery(EntityManagerImpl.java:1605)

以下是我的代码

@Entity
        @Table(name = "ASSIGN_TASK_EMPLOYEE")
        //@IdClass(AssignTaskEmployeePk.class)
        public class AssignTaskEmployee implements Serializable {

            @EmbeddedId
            private AssignTaskEmployeePk assignTaskEmployeePk;

            public AssignTaskEmployeePk getAssignTaskEmployeePk() {
                return assignTaskEmployeePk;
            }

            public void setAssignTaskEmployeePk(AssignTaskEmployeePk assignTaskEmployeePk) {
                this.assignTaskEmployeePk = assignTaskEmployeePk;
            }

        }

       @Embeddable
        public class AssignTaskEmployeePk  {

            private String employeeId;
            private String taskId;
            public AssignTaskEmployeePk() {
            }

            @Override
            public boolean equals(Object obj) {
                // TODO Auto-generated method stub

                if (obj instanceof AssignTaskEmployeePk) {

                    AssignTaskEmployeePk employeePk = (AssignTaskEmployeePk) obj;
                    if (!employeePk.getEmployeeId().equals(this.employeeId)) {
                        return false;
                    }           
                    else if (!employeePk.getTaskId().equals(this.taskId)) {
                        return false;
                    }

                }
                else {
                    return false;
                }

                return false;

            }

            @Override
            public int hashCode() {      
                return employeeId.hashCode() + taskId.hashCode() ;
            }

            public String getEmployeeId() {
                return employeeId;
            }

            public void setEmployeeId(String employeeId) {
                this.employeeId = employeeId;
            }

            public String getTaskId() {
                return taskId;
            }

            public void setTaskId(String taskId) {
                this.taskId = taskId;
            }


            }

我在数据库中为组合主键ASSIGN_TASK_EMPLOYEE（表）添加了四个值，哪个PK表

EMP_ID   TASKID
1         2
2         4
3         5
4         6 

现在，我想获取分配给emp_id 1的任务。为此，我在下面编写了查询：这应该返回AssignTaskEmployee对象的列表。

entityManager.createQuery("select t from ASSIGN_TASK_EMPLOYEE t").getResultList()

执行此查询时，出现以下异常

Exception Description: 

Problem compiling [select t from ASSIGN_TASK_EMPLOYEE t]. 
            [14, 34] The abstract schema type 'ASSIGN_TASK_EMPLOYEE' is unknown.
                at org.eclipse.persistence.internal.jpa.EntityManagerImpl.createQuery(EntityManagerImpl.java:1605)

Answer 1

JPQL应该使用实体名称，默认是类的名称。 AssignTaskEmployee

它应该是

entityManager.createQuery("select t from AssignTaskEmployee  t").getResultList()

上面将返回表ASSIGN_TASK_EMPLOYEE中的所有记录。

如果要使用JPQL检索特定记录，则应使用WHERE语句，如下所示：

    Query query =  entityManager.createQuery("select t from AssignTaskEmployee t WHERE 
t.assignTaskEmployeePk.employeeId = :employeeId and t.assignTaskEmployeePk.taskId = :taskId")

query.setParameter("employeeId", 1);
query.setParameter("taskId",1);

query.getSingleResult()  //As expected to have only one record.

阅读此内容以查询EmbeddedId