如何使用嵌入ID编写JPQL SELECT？

Question

我使用Toplink的要领（JPA）+ GlassFish的第三版+ NetBean 6.9

我有一个表与复合主键：

table (machine) 
---------------- 
|PK machineId | 
|PK workId  | 
|    | 
|______________| 

我创建2个实体类一个用于实体本身和第二个是PK类。

public class Machine { 
    @EmbeddedId 
    protected MachinePK machinePK; 

    //getter setters of fields.. 
} 

public class MachinePK { 
    @Column(name = "machineId") 
    private String machineId; 

    @Column(name = "workId") 
    private String workId; 

} 

现在.. 我怎么写SELECT子句JPQL用WHERE ???

这失败了。

SELECT m FROM Machine m WHERE m.machineId = 10 

http://www.mail-archive.com/users@openjpa.apache.org/msg03073.html

根据Web页面上，添加 “VAL”？不，它也失败了。

SELECT m FROM Machine m WHERE m.machineId.val = 10 

在这两种情况下，错误是：

Exception Description: Error compiling the query 
[SELECT m FROM Machine m WHERE m.machineId.val = 10], 
line 1, column 30: unknown state or association field 
[MachineId] of class [entity.Machine]. 

Answer 1

SELECT m FROM Machine m WHERE m.machinePK.machineId = 10 

Answer 2

测试与Hibernate 4.1和JPA 2.0

做以下修改才能工作：

类Machine.java

public class Machine { 
    @EmbeddedId 
    protected MachinePK machinePK; 

    //getter & setters... 
} 

类MachinePK.java

@Embeddable 
public class MachinePK { 
    @Column(name = "machineId") 
    private String machineId; 

    @Column(name = "workId") 
    private String workId; 

    //getter & setters... 
} 

...并为JPQL查询过所有列名：

Query query = em.createQuery("SELECT c.machinePK.machineId, c.machinePK.workId, " 
       + "FROM Machine c WHERE c.machinePK.machineId=?"); 
query.setParameter(1, "10"); 

Collection results = query.getResultList(); 

Object[] obj = null; 
List<MachinePK> objPKList = new ArrayList<MachinePK>(); 
MachinePK objPK = null; 
Iterator it = results.iterator(); 
while(it.hasNext()){ 
    obj = (Object[]) it.next(); 
    objPK = new MachinePK(); 
    objPK.setMachineId((String)obj[0]); 
    objPK.setWorkId((String)obj[1]); 
    objPKList.add(objPK); 
    System.out.println(objPK.getMachineId()); 
} 

Answer 3

如果你使用注解@Query，您可以使用元素nativeQuery = true。