Hello,
I'm trying to prototype creating a Polymorphic @Any relationship between some data.
The technologies I'm using:

1) JavaEE 7
2) Spring 4.2.2.RELEASE (Core, MVC, Data,Persistence, ORM...)
3) Hibernate 4.2.20.FINAL
4) JPA 2
5) MySql 5.6


I'm going to be brief with the class description information for the sake of brevity.

For my Entities I have the following:

@Entity
@DiscriminatorValue(value = "INDIVIDUAL")
public class Individual implements IAssignee {
@Id
@Column(name = "uuid", unique = true, nullable = false, length = 37)
private String uuid = "";
@Column(name = "firstName", unique = false, nullable = false, length = 64)
private String firstName = "";
@Column(name = "lastName", unique = false, nullable = false, length = 64)
private String lastName = "";
@Column(name = "name", unique = false, nullable = false, length = 128)
private String name = "";
...
}


@Entity
@DiscriminatorValue(value = "UGROUP")
public class UserGroup implements IAssignee {
@Id
@Column(name = "uuid", unique = true, nullable = false, length = 37)
private String uuid = "";
@Column(name = "name", unique = false, nullable = false, length = 128)
private String name = "";
...
}

public interface IAssignee {
String getUuid();
String getName();
}

@Entity
public class WorkProduct {
@Id
@Column(name = "id", unique = true, nullable = false)
private int id = 0;

@Column(name = "name", unique = true, nullable = false, length = 37)
private String name = "";

@Any(metaColumn = @Column(name = "assigneeType"))
@AnyMetaDef(idType = "string", metaType = "string", metaValues = {
@MetaValue(targetEntity = Individual.class, value = "INDIVIDUAL"),
@MetaValue(targetEntity = UserGroup.class, value = "UGROUP") })
@Cascade({ org.hibernate.annotations.CascadeType.ALL })
@JoinColumn(name = "assigneeUuid", referencedColumnName = "uuid")
private IAssignee assignee;

}

Here is the SQL table descriptions:

CREATE TABLE `individual` (
`uuid` varchar(37) NOT NULL,
`firstName` varchar(64) NOT NULL,
`lastName` varchar(64) NOT NULL,
`name` varchar(128) NOT NULL,
PRIMARY KEY (`uuid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE `usergroup` (
`uuid` varchar(37) NOT NULL,
`name` varchar(128) NOT NULL,
PRIMARY KEY (`uuid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `workproduct` (
`id` int(11) NOT NULL,
`name` varchar(37) NOT NULL,
`assigneeType` int(11) NOT NULL,
`assigneeUuid` varchar(255) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Example of data in Individual table:

uuid firstName lastName name
-------------------------------------------------
"123" "john" "smith" "jsmith"


Example of data in UserGroup table:
uuid name
------------------------
"456" "Analyst"

Example of data in WorkProduct table

ID Name AssigneeType AssigneeUUID
------------------------------------------------------
1 productA 1 "123"
2 productB 2 "456"


So here's the issues, the AssigneeType ID is an integer value from my assigneeType table

id value
--------------
1 "INDIVIDUAL"
2 "UGROUP"


My @Any relationship in WorkProduct

@Any(metaColumn = @Column(name = "assigneeType"))
@AnyMetaDef(idType = "string", metaType = "string", metaValues = {
@MetaValue(targetEntity = Individual.class, value = "INDIVIDUAL"),
@MetaValue(targetEntity = UserGroup.class, value = "UGROUP") })
@Cascade({ org.hibernate.annotations.CascadeType.ALL })
@JoinColumn(name = "assigneeUuid", referencedColumnName = "uuid")
private IAssignee assignee;

is not working because assigneeType column is an integer value.
Can someone help me fix my @Any relationship declaration?

thanks,
mbeddedsoft

Check out the @Any section on the new User Guide.

The `workproduct` product should be like this:



The workproduct should contain:



And the mapping will work.

If the SQL table cannot be modified, and the `assigneeType` must be an int, then you need to change the @Any mapping:

mihalcea_vlad,

I thank you for your reply.

I did read the Hibernate documentation and understand that Hibernate will use the Class name string by default or the string value defined by @DescriminatorValue for the 'metaColumn = @Column'. This makes it easy to perform select/insert/updates. I was able to make that work with no problem.

However, here at work, they typically used integer Type IDs defined in a Type Table (like what I described in the AssigneeType Table).

So then I guess I'm going to have to inform them that if we are to proceed using our new Hibernate/JPA solution, we will need to adapt and do it this way.

To be clear then, am I correct in understanding that it's not possible for the 'metaColumn = @Column' to refer to an Integer?
I'm only asking because they are going to ask me this question and from all the documentation and books I've read about @Any relationships and polymorphic relationships it doesn't seem to be possible.

Thank you again for your quick response. :)

The metaType can also be an integer. According to the Javadoc:



I think you need to use "integer". Did you try this mapping?

mihalcea_vlad,
I may have tried that but possibly had some other issue.

So, I went ahead and just set ASSIGNEETYPE column contain the class name for 'Individual' and 'UserGroup'. That worked fine in my prototype.

When I went to implement the same logic in our ~/dev/trunk code I keep getting this error:

MappingException: "Foreign key (FK_ovvdfqhmrpylbs1cuqcbovdf2:WORKPRODUCT [ASSIGNEETYPE,ASSIGNEEUUID])) must have same number of columns as the referenced primary key (INDIVIDUAL [UUID])"

Do you have any Idea what this is referring to?

I made changes to ~/dev/trunk classes for Individual and UserGroup so that they implement my IAssignee interface.
I also updated both classes so that they both have Primarykey named 'UUID' and a 'NAME' as defined by my interface.

I'm confused at the MappingException message.

mbeddedsoft

I figured out the problem.

I have a bi-directional relation in my Individual to WorkProduct.

// bi-directional many-to-one association to WorkProduct
@OneToMany(mappedBy = "assignee")
private Set<WorkProduct> assignedWorkdProducts = TreeSet<WorkProduct>();

I commented out this in my Individual class and everything worked fine.

I think I need to figure out how to use a composite key mapping here because WorkProduct.assignee is the IAssignee assginee property mapped by the @Any relationship and uses the AsssigneeType and AssigneeUuid columns.


mbeddedsoft

Sigh,
Ok now I need help querying by Assignee.uuid parameter.

Here is my query code:

final String str= "select p from WorkProduct p where p.assignee.uuid ='123'";
final Query query = session.createQuery(str);
final List<String> list = query.list();

session.createQuery(str) throws this QueryException:
could not resolve property: assignee.uuid of: org.baeldung.persistence.entities.WorkProduct [select p from com.test.entities.WorkProduct p where p.assignee.uuid ='123']

I have data in the WorkProduct table.
If I use this query string "select p from WorkProduct p" everything works and I can iterate through the list and determine IAssignee types and see their properties after casting them appropriately.
However, I need to be able to query Workproducts by Assignee.uuid and I'm stuck.

I even tried this query "select p from WorkProduct p where (TYPE(p.assignee) = Individual and p.assignee.uuid ='123')" and got the same exception on p.assignee.uuid property.

Any thoughts or suggestions?

thanks,
mbeddedsoft