hibernate mapping problem
To: comp.lang.java.databases
Hi folks,
I have a problem using Hibernate Annotations. I try to map the following
entity relation_
ER-Diagram:
+------+ 1 * +-------------------+ * 1 +------+
|ClassA| ------<>----- |ClassAClassBMapping| -----<>----- |ClassB|
+------+ +-------------------+ +------+
Intention:
a unidirectional mapping of ClassB to ClassA without a special entity
for ClassAClassBMapping
The following Scenario is working:
Enum MyEnum{
A,B,C
}
@Entity (name="entity_a")
@Table(name="table_a")
class ClassA {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@OneToMany(targetEntity = ClassB.class)
@MapKey(name = "classb_id")
@JoinTable(name = "ClassAClassBMapping", joinColumns =
@JoinColumn(columnDefinition = "classa_id", table = "table_a", name =
"id", nullable = false),
inverseJoinColumns = @JoinColumn(columnDefinition =
"classb_id", table = "table_b", name = "id", nullable = false),
uniqueConstraints = @UniqueConstraint(columnNames = {
"classa_id", "classb_id"
}))
private Map<MyEnum,ClassB> bClasses;
}
@Entity (name="entity_b")
@Table(name="table_b")
ClassB {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@Embedded
private MyEnum myEnum;
}
The trouble with this solution is the point, that the enumeration is not
a property of ClassB but classification of ClassB in ClassA. As I use
the enumeration as a property I will get lots of redundant datasets,
that slowdown the application and make it difficult to handle modifications.
My favored solution is shown below but that solution doesn't work.
Entities:
@Embeddable
Enum MyEnum{
A,B,C
}
@Entity (name="entity_a")
@Table(name="table_a")
class ClassA {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@OneToMany(targetEntity = ClassB.class)
@MapKey(name = "myEnum")
@JoinTable(name = "ClassAClassBMapping", joinColumns =
@JoinColumn(columnDefinition = "classa_id", table = "table_a", name =
"id", nullable = false),
inverseJoinColumns = @JoinColumn(columnDefinition =
"classb_id", table = "table_b", name = "id", nullable = false),
uniqueConstraints = @UniqueConstraint(columnNames = {
"classa_id", "myEnum"
}))
private Map<MyEnum,ClassB> bClasses;
}
@Entity (name="entity_b")
@Table(name="table_b")
ClassB {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
}
I cannot deliver an errormessage, because spring-framework only reports
that the sessionfactory cannot be instantiated. As soon as I remove the
mapping or change the mapping to the first example all JUnit-tests work
fine. So I am sure that the configuration of spring is ok.
Any idea's what is the problem?
Kind Regards
Mark
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