A have this mapping:
mapping.HasManyToMany(x => x.SubVersions).ParentKeyColumn("ParentId").ChildKeyColumn("SubVersionId").Table(
"VersionLinks");
This will create a table VersionLinks with 2 columns(ParentId,SubVersionId). Is it possible to have in this table another column (ex. CreateDate) that will be filled automaticly (DateTiem.Now) without creating a new entity VersionLink with fields Parent, SubVersion, Date?
You could try to create the new CreateDate column manually with a default getdate() value, but I'd just create a new entity for VersionLink and convert the many-to-many to many-to-ones
For auto updating the date property, take a look at using the IPreUpdateEventListener.
As for the mapping table, I'm pretty sure you're stuck with having to create a composite-element. I had a similar issue where I wanted to add sort and weight columns. I ended up with the following mapping:
<bag
name="criteria"
access="field"
table="assessment_criterion_map"
fetch="subselect"
cascade="save-update">
<key column="assessment_id"/>
<composite-element class="WeightedCriterion">
<parent name="assessment"/>
<many-to-one
class="Criterion"
name="criterion"
access="field"
column="criterion_id"
cascade="save-update"
fetch="join"/>
<property name="Weight"/>
<property name="SortOrder" column="sort_order"/>
</composite-element>
</bag>
Related
I'm struggling with a NHibernate related problem where I could use some input.
Introduction:
I have a legacy database where the relational concepts have not really been applied.
In the database I have an OrderLine table which contains data for an order lines.
On top of that the table also contains all columns with Order specific information. This could for example be order number of a customer.
E.x. If i have 10 order lines - then I have 10 rows in my OrderLines table and each row has all the Order specific data e.g. order number or customer information.
I did not want to have the above structure in my code so a view was created for Orders so that I could map my Order in NHibernate which then has a set/bag of OrderLines which makes much more sense.
Mapping: (simplified)
<class name="Order" table="[view_Orders]">
<bag name="OrderLines">
</class>
<class name="OrderLine" table="OrderLines" />
The problem:
The complexity of the view makes it impossible to save to the view. When trying NHibernates throws this exception:
NHibernate.Exceptions.GenericADOException: could not insert: XXX ---> System.Data.SqlClient.SqlException: View or function 'view_Orders' is not updatable because the modification affects multiple base tables.
My NHibernate mapping is constructed as an Order object which has a "set or bag" of OrderLine objects. Ideally I would like NHibernate only to persist the set of OrderLine objects instead of the whole object.
Is there a way of achieving this? I have tried locking the object using different lock modes but it did not help me.
You can use mutable="false" to avoid the update and deletes as this article says:
Immutable classes, mutable="false", may not be updated or deleted by the application. This allows NHibernate to make some minor performance optimizations.
To avoid the insert you can use the following statement (Uses the proyection instead an insert command, dont forget use check="none"):
<sql-insert check="none">SELECT 1</sql-insert>
Here is a tested example:
<class name="Order" table="[view_Orders]" mutable="false">
<id name="OrderId" type="System.Guid">
<generator class="guid.comb"/> <!-- Change as you need -->
</id>
<!-- Other properties -->
<!-- <property name="GrandTotal"/> -->
<set name="OrderLines" lazy="true" inverse="true" cascade="all-delete-orphan">
<key column="OrderId"/>
<one-to-many class="OrderLine"/>
</set>
<sql-insert check="none">SELECT 1</sql-insert>
</class>
<class name="OrderLine" table="OrderLine">
<id name="OrderLineId" type="System.Guid">
<generator class="guid.comb"/> <!-- Change as you need -->
</id>
<!-- Other properties -->
<!-- <property name="OrderId"/>
<property name="GrandTotal"/>/> -->
</class>
In case I do understand your issue, the solution is surprisingly simple. We just would mark root object with dynamic-update="true"
<class name="Order" table="[view_Orders]" dynamic-update="true">
...
</class>
And then apply update="false" to every property or reference which we have in that Order class mapped to view:
...
<property name="Code" update="false"/>
...
<many-to-one name="Country" update="false />
But our collection will need the standard, even cascade mapping:
<class name="Order" table="[view_Orders]" dynamic-update="true">
<bag name="OrderLines"
lazy="true"
inverse="true"
batch-size="25"
cascade="all-delete-orphan" >
...
</bag>
... // other stuff is update="false"
</class>
And now code like this would do management of OrderLines, while not executing any updates on the root object Order
var session = ... // get ISession
// load root
var root = session.Get<Order>(123);
// if needed change existing line (pretend there is one)
root.OrderLines[0].Amount = 100;
// add new
var newOrder = ... // new order
root.OrderLines.Add(newOrder);
session.Save(root);
session.Flush();
And that is it. Cascade on the root object is doing what we need, while the update="false" is not updating it...
NOTE: Just interesting note - there is also class and collection
setting mutable="false", but it would not work here... as the
solution mentioned above (it is sad, because that would be more
elegant, but not working as expected...). See:
19.2.2. Strategy: read only
If your application needs to read but never modify instances of a persistent class, a read-only cache may be used. This is the simplest and best performing strategy. Its even perfectly safe for use in a cluster.
<class name="Eg.Immutable" mutable="false">
I am mapping the following entities using NHibernate:
+ Party (abstract)
- Employee
- Customer
I am using the mapping strategy called: joined-subclass in the following way:
<!-- Base PARTY entity-->
<class name="PartyMap" abstract="true" table="Party">
<id name="Id" column="PartyID">
<generator class="guid.comb" />
</id>
<joined-subclass table="Customer" name="Customer">
<key column="CustomerID" />
</joined-subclass>
<joined-subclass table="Employee" name="Employee">
<key column="EmployeeID" />
</joined-subclass>
</class>
My problem is that inside the Party table I have the following structure:
PartyTable
PartyID
EmployeeID
CustomerID
While NHibernate use the Id field for every child table mapped. Should I use a different approach like component to achieve my goal?
One possible solution that I have found is to implement an event listner on top of NHibernate framework so that every time an entity is saved I can control the values passed and fix the error with the Guid without the need to create crazy Stored Procedures.
I know it's ugly but the database is legacy so there is not really much I can do
I know it has been asked for many times, i also have found a lot of answers on this website, but i just cannot get out this problem.
Can anyone help me with this piece of code?
Many thanks.
Here is my parent mapping file
<set name="ProductPictureList" table="[ProductPicture]" lazy="true" order-by="DateCreated" inverse="true" cascade="all-delete-orphan" >
<key column="ProductID"/>
<one-to-many class="ProductPicture"/>
</set>
Here is my child mapping file
<class name="ProductPicture" table="[ProductPicture]" lazy="true">
<id name="ProductPictureID">
<generator class="identity" />
</id>
<property name="ProductID" type="Int32"></property>
<property name="PictureName" type="String"></property>
<property name="DateCreated" type="DateTime"></property>
</class>
Here is my c# code
var item = _productRepository.Get(productID);
var productPictrue = item.ProductPictureList
.OfType<ProductPicture>()
.Where(x => x.ProductPictureID == productPictureID);
// reomve the finding item
var ok = item.ProductPictureList.Remove(productPictrue);
_productRepository.SaveOrUpdate(item);
ok is false value and this child object is still in my database.
Not 100% sure, but could be because you have defined ProductID as a property of ProductPicture, I assume this is the PK from the Product class. You don't need to add this again, it will be created by the relationship.
I'm not sure that your use of table="[ProductPicture]" in the set tag is right.
The one-to-many tag already establishes the link between ProductPictureList and ProductPicture.
I think the table attribute is generally for using a separate relationship table when modelling many-to-may relationships.
From nhibernate.info Doc:
table (optional - defaults to property name) the name of the
collection table (not used for one-to-many associations)
And:
A collection table is required for any collection of values and any
collection of references to other entities mapped as a many-to-many
association
Let's start with this mapping:
<component name="Location">
...
<property name="Settings" type="JsonUserType,...">
<column name="LocationSettingsType" />
<column name="LocationSettingsData" />
</property>
</component>
This maps to
TABLE Primary (
...
LocationSettingsType,
LocationSettingsData
...
)
and
class Location {
...
object Settings { get; set; }
}
Now, I want to extract settings into a separate table (because they are seldom here).
So I get
TABLE Primary (
...
LocationSettingsId,
...
)
TABLE Settings (
Id,
Type,
Data
)
Can I keep my C# classes the same?
Update: This is not a many-to-one relationship. As before, each location has zero or one settings, and each settings belong to at most one location.
I believe the closest thing that exists to this is the <map> mapping element; details are explained in this article.
If you want a one to many relationship on the Primary and Settings tables, you'll have to set a foreign key constraint first. Then you'll use the bag property in XML to map your tables. You will have an entity for each table.
See also this question on NHibernate/FluentNHibernate Property Bag.
I also recommend you purchase the NHibernate 2 for Beginners book. It helped me alot.
This is an old question but i had the same issue and looking to a solution I came here.
the component element can map several columns to several object models.
the join element can map several tables to an object model.
The main problem is that while the component cannot map columns from a different table where the model belong, the join cannot map the different table columns to a different object model.
The solution I found is to use both to achieve the map column of a different table to several object:
<class name="Primary" table="Primary">
<id name="Id">
<generator class="identity"/>
</id>
<property name="Name" />
...
<join table="Settings">
<key column="PrimaryId"/>
<component name="Location">
...
<property name="Settings" type="JsonUserType,...">
<column name="LocationSettingsType" />
<column name="LocationSettingsData" />
</property>
</component>
</join>
</class>
Reference:
NHibernate Join mapping element
NHibernate Component mapping element
I am working with nHibernate, and trying make sense of bag collections. My data structure is relatively straight-forward...
Entry:
<class name="Entry">
<id name="id" column="EntryId">
<generator type="guid.comb"/>
</id>
<property name="Name" column="Name"/>
<bag name="Results" table="Results" cascade="all">
<key column="EntryId" />
<one-to-many class="Result"/>
</bag>
</class>
Result:
<class name="Result">
<id name="id" column="ResultId">
<generator type="guid.comb"/>
</id>
<property name="Score" column="Score" />
<many-to-one name="Entry" class="Entry" cascade="all" />
</class>
What I would like to do, which doesn't seem to be working, is the following:
Entry entry = new Entry();
entry.Name = "Name";
// have tried saving at this point to:
// dbSession.SaveOrUpdate(entry);
Result result = new Result();
result.Score = 100;
entry.Results.Add(result);
dbSession.SaveOrUpdate(entry);
It seems to be creating the entry record in the database, but not the result record. In my database, I have EntryId as a foreign key in the Result table. Similarly, I would like to be able to remove the result object from the collection, and have it persist to the database. I thought the cascade feature took care of this, but not sure what I have done wrong...
EDIT
I now have it adding the result object into the database, but delete does not seem to work:
Entry entry = Entry.Load(id);
entry.Results.Remove(result);
dbSession.SaveOrUpdate(entry);
I have tried adding cascade="all-delete-orphan", but this seems to remove both parent and children. I just want it to delete the one entry object from the database??
In the end, this came down to my hbm file mappings not being correct.
Entry.hbm.xml
<bag name="Results" table="Result" lazy="false" inverse="true" cascade="all-delete-orphan">
<key column="EntryId"/>
<one-to-many class="Result"/>
</bag>
Result.hbm.xml
<many-to-one name="Entry" class="Entry" column="EntryId"/>
I originally had cascade="all-delete-orphan" on the many-to-one mapping, which was not correct. What happened was that all children and the parent record was being deleted.
I can now add and remove with the following:
Result r = new Result();
Entry entry = new Entry();
// AddResult method sets the Entry object of the Result
// result.Entry = this;
entry.AddResult(r);
session.SaveOrUpdate(entry);
To delete:
entry.Results.Remove(result);
session.SaveOrUpdate(entry);
To add to a collection you need to explicitly save the child object when it is added. Ditto when you delete an object from a collection.
So you would do:
entry.Results.Add(result);
session.Save(result);
session.Save(entry);
session.Flush();
The foreign key also has to be nullable. The reason why you have to do this is NHibernate has to save the child first with no association to the parent. Then when the parent is saved the foreign key column on the child gets updated with the parent's Id, creating the relation. This is because NHibernate may not have the needed parent id key value until the second operation (parent is saved) has completed.
I guess you have this part figured out.
Delete works the same way for different reasons - remove the child from the parent collection, then delete the child explicitly, then update the parent:
entry.Results.Remove(result);
session.Delete(result);
session.Update(entry);
session.Flush();
You removed result from the collection and updated the entry. That only tells Nhibernate to delete the relationship between the entry and the result - you never actually deleted the result object itself.
I notice that, in your collection, you have defined the FK column as:
<key column="EntryId" />
But you are not overriding the column in your many-to-one, which means you have two different columns (Entry and EntryId) for the same relationship.
This might be it or not... but it doesn't hurt to check :-)
if you are using Mapping by Code then use both Cascade.All and Cascade.DeleteOrphans options. unlike the xml mapping, there is no single option for "all-delete-orphan" in Mapping by Code.
Bag(x => x.Results, c =>
{
c.Key(k =>
{
k.Column("EntryId");
});
c.Cascade(Cascade.All | Cascade.DeleteOrphans);
}, r => r.OneToMany())