I have two entities Account and Position. The POSITION table and the ACCOUNT table have contents but the POSITION_ACCOUNT table, which I think should have at least one row, is empty. What could I be doing wrong? Here is the relevant code (I am using EclipseLink 2.4.2:
In Position:
#ManyToMany
private List accounts;
In Account:
#ManyToMany(mappedBy = "accounts",fetch=FetchType.EAGER,cascade=CascadeType.PERSIST)
#JoinTable(name="POSITION_ACCOUNT")
Confusing to me and perhaps relevant is that some examples I see annotate the getters and setters but others, as I am doing here, annotate the actual Lists.
It turns out that I needed to specify cascade=CascadeType.PERSIST on both sides of the relationship but there were other application-specific issues along the way. I don't know if reading the original question or this answer will be of much help to anyone. Sorry.
Related
I need some help today related to EF relationship. I have two lookup tables Country and Ethnicity. I want to have nullable foreign keys for both in one my table named Singles, so I defined a relationship in my class like
Single Relation
that generate a table like this, which is good so far
Single Relation Result
But I have other fields like Citizenship and CountryOfBirth which require a foreign key as well from Country table. So, I tried to do the same
Multiple Relation with Same Class
But things getting weird inside sql when table created.
Multiple Relation with Same Class Result
I can understand why it behaves odd but don't know how to make it work. Can you please suggest?
Thanks
You'll need to place your ForeignKey attributes on the navigational properties to point to the nullable ID field (instead of vice-versa), and then use the InverseProperty attribute to properly tell EF exactly what kind of relationship you are trying to accomplish.
This answer will be quite similar to that in this SO question.
I have a dumb question. It would be great if this could be done, but I am not holding my breath.
I need a single column from a table linked to my JPA entity to be a collection in said JPA entity. Is there any way, that I can just get back that column alone that is related to that entity, instead of having to get back an entire table (which could be very costly?)
Can I perform a query inside that JPA entity that will be performed and loaded eagerly into a collection?
I am trying to avoid having to make several calls to the database by just executing a couple of queries.
What are your thoughts on this?
#ElementCollection(fetch=FetchType.EAGER)
#CollectionTable(name="QUICK_LAUNCH_DISTLIST",joinColumns=#JoinColumn(name="QUICK_LAUNCH_ID"))
#Column(name="LIST_ID")
private List<Long> distListIDs;
The ElementCollection attribute is what I was looking for. It seems to work pretty well in addition to that.
Thanks for the help and inspiration guys.
Suppose a Category has many products:
select product.name from Category c inner join c.products product where ...
If that's not what you want, please show an example in your question.
Sure this is a simple answer, but I cannot find the right source to give the details.
I have a ManyToOne relationship. Because of a synchronization system, when a child is removed a field named 'removed' is set to 'true', and will automatically be deleted only a month later.
However, in the meanwhile, I would like it not to appear in the List in the parent. Is there an easy way to specify a select statement in the definition of the field or so?
#OneToMany(mappedBy = "parent")
#OrderBy("level")
public List<MenuItem> children;
As you are using hibernate you can use the #where annotation. I never used it myself but it seems quite straight forward. Have a look here: http://docs.jboss.org/hibernate/stable/annotations/reference/en/html_single/#entity-hibspec-collection
I have users and each user has several roles. Roles and users are in many-to-many relationship. But the role is just a name. I've got stuck in this phase:
#ManyToMany
#JoinTable(name="users2roles")
private Collection<String> roles;
There is missing the name of target table. I was searching on Internet, but nothing have found. I don't wannt to create special entity class to wrap one string value. Is there some another way, isn't?
Is there any way to make it work or makes JPA me create a new entity?
A Collection of Strings isn't relating one object to another so cannot be a #OneToMany or #ManyToMany - ought to be #ElementCollection. It's a collection of Strings, nothing more. Yes, it can be stored in a join table, but using #CollectionTable.
I have the following tables in the database (just a demo, of course):
Positions
PositionId
Limits
LimitId
PositionId
I want to left join them into a single entity (always have position, not always have a limit attached to it):
Position
PositionId
LimitId
I've seen articles regarding one-to-one mapping and "Table per type inheritence", and tried to implement the same method here, but with no sucess. Is that even possible?
I think what you want is an ordinary inner join where your foreign key (PositionID in the Limits table) is allowed to be null.
Yes and no...In my scenario, the 2nd option is the applicable one, since I don't have the same primary key in both tables. so, I must create an updateable view...The problem with updateable view is that I can't modify fields which are in different tables and expect the database to handle it, unless I use "Instead of" triggers, which I really don't want to get into at all...
So, I guess there's nothing out of the box for me...damn.
(Unless you have another idea...)
Anyways, I really thank you for your help, it's much appreciated.
Nir.