我尝试对以下实体图进行 JPQL 查询:Derived1 和 Derived2 是 ReferencedEntity 的子类。主实体有一个 ReferencedEntity 列表。现在假设每个 MainEntity 的列表中只有一个 Derived1 和 Derived2 的实例。
+--------------+
| MainEntity |
+--------------+ +------------------+
| list | --- OneToMany ---> | ReferencedEntity |
+--------------+ +------------------+
| String a1 |
+------------------+
^
|
+-----------+-----------+
| |
+--------------+ +--------------+
| Derived1 | | Derived2 |
+--------------+ +--------------+
| String d1 | | String d2 |
+--------------+ +--------------+
现在我想通过它们在列表中包含的 d1 和 d2 值对 MainEntities 进行分组。因此,我编写了以下 JPQL 查询:
SELECT COUNT(m) FROM MainEntity m JOIN TREAT(m.list AS Derived1) der1, TREAT(m.list AS Derived2) der2 GROUP BY der1.d1, der2.d2
我认为这应该可行,但我得到:
Caused by: Exception [EclipseLink-0] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.JPQLException
Exception Description: Syntax error parsing [SELECT COUNT(m) from MainEntity m JOIN TREAT(m.list AS Derived1) der1, TREAT(m.list AS Derived2) der2 GROUP BY der1.d1, der2.d2].
[83, 84] The FROM clause has 'TREAT(m.list' and 'AS Derived2' that are not separated by a comma.
[83, 83] The right parenthesis is missing from the sub-expression.
[77, 83] The identification variable 'm.list' is not following the rules for a Java identifier.
[84, 84] A "root object" must be specified.
[95, 127] The query contains a malformed ending.
at org.eclipse.persistence.internal.jpa.jpql.HermesParser.buildException(HermesParser.java:155)
at org.eclipse.persistence.internal.jpa.jpql.HermesParser.validate(HermesParser.java:334)
at org.eclipse.persistence.internal.jpa.jpql.HermesParser.populateQueryImp(HermesParser.java:278)
at org.eclipse.persistence.internal.jpa.jpql.HermesParser.buildQuery(HermesParser.java:163)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:142)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:116)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.<init>(EJBQueryImpl.java:102)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.<init>(EJBQueryImpl.java:86)
at org.eclipse.persistence.internal.jpa.EntityManagerImpl.createQuery(EntityManagerImpl.java:1583)
... 2 more
Java Result: 1
仅出于测试目的,我尝试了不同的连接:
SELECT COUNT(m) FROM MainEntity m JOIN TREAT(m.list AS Derived1) der1, m.list refd GROUP BY der1.d1, refd.a1
这个有效并提供了结果。
然后我尝试了第三个查询,只是改变了连接的顺序:
SELECT COUNT(m) FROM MainEntity m JOIN m.list refd, TREAT(m.list AS Derived1) der1 GROUP BY der1.d1, refd.a1
这会导致完全相同的异常(但这次是 Derived1)。
Caused by: Exception [EclipseLink-0] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.JPQLException
Exception Description: Syntax error parsing [SELECT COUNT(m) from MainEntity m JOIN m.list refd, TREAT(m.list AS Derived1) der1 GROUP BY der1.d1, refd.a1].
[64, 65] The FROM clause has 'TREAT(m.list' and 'AS Derived1' that are not separated by a comma.
[64, 64] The right parenthesis is missing from the sub-expression.
[58, 64] The identification variable 'm.list' is not following the rules for a Java identifier.
[65, 65] A "root object" must be specified.
[76, 108] The query contains a malformed ending.
at org.eclipse.persistence.internal.jpa.jpql.HermesParser.buildException(HermesParser.java:155)
at org.eclipse.persistence.internal.jpa.jpql.HermesParser.validate(HermesParser.java:334)
at org.eclipse.persistence.internal.jpa.jpql.HermesParser.populateQueryImp(HermesParser.java:278)
at org.eclipse.persistence.internal.jpa.jpql.HermesParser.buildQuery(HermesParser.java:163)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:142)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:116)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.<init>(EJBQueryImpl.java:102)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.<init>(EJBQueryImpl.java:86)
at org.eclipse.persistence.internal.jpa.EntityManagerImpl.createQuery(EntityManagerImpl.java:1583)
... 2 more
Java Result: 1
对我来说,EclipseLink 中可能存在错误,或者我是否正在尝试一些被禁止的东西?