Having trouble with implementing second level cache in Nhibernate. I have a class mapped as follows:
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Data" namespace="Data">
<class name="Account" table="Accounts" lazy="false">
<cache region="Standard" usage="read-write" include="all"/>
<id column="ID" name="ID">
<generator class="assigned" />
</id>
<version name="VersionStamp" column="VersionStamp" type="integer" unsaved-value="0" />
<property name="Name" not-null="true" />
<property name="Type" not-null="true" />
<property name="ClientID" not-null="true" insert="false" update="false" />
<property name="DateCreated" not-null="true" type="UtcDateTime" />
<property name="LastUpdatedDate" not-null="true" type="UtcDateTime" />
<property name="IsActive" not-null="true" />
<many-to-one name="Client" class="Client" column="ClientID" not-found="exception" not-null="true" />
</class>
</hibernate-mapping>
The property "ClientID" is a foreign key into the Clients table and the Client many-to-one property uses it to look up the associated client object.
When I add a new Account, I look up the Client object from the database with a Session.Get and assign it to my Account object's Client property. Behind the scenes, this also automatically populates the ClientID property when the object is written to the database, and the ID is correctly stored in the database. When I retrieve the Account object from the database by ID using Session.Get, all the fields are populated correctly when the object is retrieved.
However, when I implement the second level cache using the settings shown above, the ClientID property is NOT populated when the Account object is retrieved using Session.Get, but the Client property is populated correctly. Is there some reason why this will not work with second level cache? Or have I done something wrong in my mapping/configuration?
For now I am just using SysCache as my caching provider, and both query and second level cache are turned on. The Client class mapping contains a corresponding one-to-many property for the Accounts.
I like the convenience of having the ClientID property on my Account class, so that I can read it without using the Client property, and it seems to work fine without caching.
Thanks for any help.
Rich
I tried to reproduce your situation locally. With your mapping (used the same as the snippet above) I was able to get incorrect behaviour only on UPDATE. In that case, the ClientID was cached, and while the Client reference was changed, the ClientID remained unchanged. In other cases caching was working as expected.
The solution is to change the mapping. The below suggested mapping is the most suitable for read-only properties like ClientID. (I am using that approach as well).
<property name="ClientID" formula="[ClientId]"
not-null="true" insert="false" update="false" />
So the trick is in the formula mapping instead of Column (the default when none is provided)
Related
I recently tried to develope a "SessionWrapper". The idea behind it was to be able to switch from a Stateful Session to a Stateless Session easily, with no modifications to the DAOs and the XML mapping files.
Mapping looks like this:
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="Domain" assembly=Domain">
<class name="BatchScheduling" table="dbo.batch_scheduling">
<id name="ID" column="batch_scheduling_id">
<generator class="native" />
</id>
<property name="Name" column="batch_scheduling_name" not-null="true" />
<property name="Description" column="batch_scheduling_description" not-null="true" />
<property name="Type" column="batch_scheduling_type" not-null="true" />
<property name="Cron" column="batch_scheduling_cron" not-null="true" />
<property name="DateModified" column="batch_scheduling_date_modified" not-null="true" />
<bag name="Parameters" cascade="all" table="dbo.batch_scheduling_parameters" lazy="true" inverse="true">
<key column="batch_scheduling_id"/>
<one-to-many class="BatchSchedulingParameter"/>
</bag>
</class>
</hibernate-mapping>
I knew that Stateless Sessions do not support lazy loading. I expected the session to eager fetch all the related objects/collections declared in the mapping.
However, when I try to access BatchScheduling.Parameters I get the following exception:
NHibernate.LazyInitializationException: Initializing[Domain.BatchScheduling#22]-failed to lazily initialize a collection of role: Domain.BatchScheduling.Parameters, no session or session was closed
Any idea?
I knew that Stateless Sessions do not support lazy loading. I expected the session to eager fetch all the related objects/collections declared in the mapping.
That could result in the entire database being loaded into memory, and will in probably 80-90% of cases result in way more queries than are necessary and basically render the stateless session useless.
One approach you can use is to eagerly fetch the relationships you need, using something like SetFetchMode
I have two classes: Family and Address.
A family has a physical address and a mailing address.
The mapping file for Family looks like:
....
<id name="Id" column="Id" type="Int32" unsaved-value="0">
<generator class="native"></generator>
</id>
<many-to-one name="PhysicalAddress" class="Address" column="PhysicalAddressId" cascade="all" unique="true" />
<many-to-one name="MailingAddress" class="Address" column="MailingAddressId" cascade="all" unique="true" />
...
The mapping file for Address looks like:
...
<id name="Id" column="Id" type="Int32" unsaved-value="0">
<generator class="native"></generator>
</id>
<property name="StreetAddress1" column="StreetAddress1" />
<property name="StreetAddress2" column="StreetAddress2"/>
<property name="City" column="City" />
<property name="State" column="State" />
<property name="ZipCode" column="ZipCode" />
...
(Note that Family-PhysicalAddress and Family-MailingAddress are one-to-one relationships.)
What I would like to happen is that when I execute
aFamily.MailingAddress = null;
session.Save(aFamily);
session.Flush();
I expect NHibernate to automatically delete the mailing address record from SQL Server for me.
BUT, that doesn't happen. NHibernate does not delete the address record from SQL Server.
Is there any way I can make it work?
Thank you!
This behaviour isn't supported by NHibernate. Of course the problem is that you probably don't have access to the NHibernate session in your domain logic where the change is made.
One possible -- though admittedly not ideal solution -- is to simply run another process to clean up orphaned entities.
Here is a discussion of this scenario:
http://colinjack.blogspot.com/2008/03/nhibernate-gotchas-orphans-and-one-to.html
And a link to a ticket on the issue:
https://nhibernate.jira.com/browse/NH-1262
Unfortunately NHibernate currently does not support automatic deletions of orhphans for many-to-one (Hibernate v3 in Java does support it). It is only supported on lists (cascade="all-delete-orphan").
What you can try to do is to use component mapping. Maybe it is possible to embed many-to-one into a component.
But I think it would better to explicitly delete the related object.
I have an application that has a core assembly with base classes that I need to inherit from.. I need to save these to the database and after reading about NHibernate decided to use it.
However I have a problem with one of my new inherited classes.. I have setup the subclass map but when I save, it neither attempts to save any of it's base class properties or any of it's new ones that I have assigned in the mapping!
My classes are laid out like the following: (from a small demo app)
core assemblies
DataItem -> User
Anything that will touch the database inherits the DataItem class as it handles the id, modified date etc etc..
In my test I setup user to only have a FirstName..
If I save a new User it works great.. however when I inherit from user and then add another property called LastName and attempt to save this new object.. it only puts a sql statement together of INSERT INTO t_User (id) VALUES(?).. it doesn't attempt to save the first name or last name.. either though both have been set and are mapped.
My nhibernate.config:
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">
<session-factory name="DAL">
<property name="dialect">NHibernate.Dialect.MsSql2005Dialect</property>
<property name="connection.provider">NHibernate.Connection.DriverConnectionProvider</property>
<property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property>
<property name="adonet.batch_size">16</property>
<property name="current_session_context_class">web</property>
<property name="proxyfactory.factory_class">NHibernate.ByteCode.Castle.ProxyFactoryFactory, NHibernate.ByteCode.Castle</property>
<mapping assembly="DAL"/>
<mapping assembly="NHibernateDemo"/>
</session-factory>
</hibernate-configuration>
As you can see I have 2 assemblies.. my DAL is my core and the NHibernateDemo is a web application that uses the core for inheritance.
My core DataItem mapping:
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="DAL" namespace="DAL.Model">
<class name="DataItem" table="t_DataItem" >
<id name="Id">
<generator class="native" />
</id>
<discriminator column="typeid" type="System.Int32"></discriminator>
<property name="IsActive" column="isActive" not-null="true" />
<property name="TypeId" column="typeId" not-null="true"></property>
<many-to-one name="Parent" column="ParentId" class="DataItem"></many-to-one>
<bag name="Children" cascade="all-delete-orphan">
<key column="ParentId"></key>
<one-to-many class="DataItem"/>
</bag>
<joined-subclass name="User" table="t_Users">
<key column="id"></key>
<property name="FirstName" column="firstName" not-null="true" ></property>
</joined-subclass>
<joined-subclass name="Email" table="t_Emails">
<key column="emailid"></key>
<property name="Address" column="Address"></property>
</joined-subclass>
</class>
</hibernate-mapping>
My inherited NewUser mapping that doesn't work!:
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="NHibernateDemo" namespace="NHibernateDemo.Model">
<subclass name="NewUser" extends="DAL.Model.User, DAL" discriminator-value="1">
<property name="LastName" column="LastName"></property>
</subclass>
Why is it that when I attempt to save my class NewUser that it doesn't attempt to save any of the other properties set, whether from it's base or newly declared properties?
I'd really appreciate any help or insight to this.. I must be missing something really simple and I just can't see it.
Thanks,
Mike
It could be that you're not able to mix subclass and joined-subclass mappings in the same class hierarchy. Since your DataItem and User are related by joined-subclass, you may need to make your NewUser class another joined-subclass of User.
Another issue might be the use of the "discriminator" in your current NewUser mapping. The discriminator should be an additional column in your User table that NHibernate uses to tell the difference between a User record and a NewUser record. I'm not sure if this works where the User base class might not specify its discriminator value, whereas the NewUser does. I'm not sure if you're specifying the discriminator-column anywhere, which might also be a problem.
I would suggest first trying to make NewUser a joined-subclass of User.
I have a base class for content items in a CMS I'm building. It's currently marked abstract because I only want derived classes to be instantiated. Derived classes like BlogPost, Article, Photo, etc. are set up as a joined subclass to my ContentBase class in nHibernate.
I'm trying to set up a many-to-many mapping between this class and a Tag class. I want to have a collection of Tags on the ContentBase class, and a collection of ContentBase items on the tag class.
Will nHibernate allow me to map the abstract ContentBase class as a collection on the Tag class? I'm assuming not since it wouldn't be able to instantiate any instances of this class when reconstituting a Tag entity from the db. I really don't want to have to have to use a collection of content items per type (e.g. TaggedBlogPosts, TaggedArticles, etc.) on the Tag class.
The whole reason I'm doing this is because logically, a content item can have many tags, and 1 tag can belong to multiple content items. in order for nHibernate to manage the relationships for me in a mapping table, I believe I have to set up a many-to-many association and add the Tag to the ContentBase.Tags collection and then the content item to the Tags.TaggedContentItems collection before the mapping table entry is created in nHibernate.
Here are my mappings for reference:
<class name="CMS.Core.Model.Tag,CMS.Core" table="bp_Tags">
<id column="TagName" name="TagName" type="String" unsaved-value="">
<generator class="assigned" />
</id>
<bag name="_taggedContentList" table="bp_Tags_Mappings" inverse="true" cascade="save-update" lazy="true">
<key column="TagName" />
<many-to-many class="CMS.Core.Model.ContentBase,CMS.Core" column="Target_Id" />
</bag>
</class>
<class name="CMS.Core.Model.ContentBase,CMS.Core" table="bp_Content">
<id name="Id" column="Id" type="Int32" unsaved-value="0">
<generator class="native"></generator>
</id>
<property name="SubmittedBy" column="SubmittedBy" type="string" length="256" not-null="true" />
<property name="SubmittedDate" column="SubmittedDate" type="datetime" not-null="true" />
<property name="PublishDate" column="PublishDate" type="datetime" not-null="true" />
<property name="State" column="State" type="CMS.Core.Model.ContentStates,CMS.Core" not-null="true" />
<property name="ContentType" column="ContentType" type="CMS.Core.Model.ContentTypes,CMS.Core" not-null="true" />
<bag name="_tagsList" table="bp_Tags_Mappings" lazy="false" cascade="save-update">
<key column="Target_Id" />
<many-to-many class="CMS.Core.Model.Tag,CMS.Core" column="TagName" lazy="false" />
</bag>
...
<joined-subclass name="CMS.Core.Model.BlogPost,CMS.Core" table="bp_Content_BlogPosts" >
<key column="Id" />
<property name="Body" type="string" column="Body" />
<property name="Title" type="string" column="Title" />
</joined-subclass>
...
I would also assume that Hibernate would need to instantiate the base class, which makes sense, as there is data directly linked to it in the DB.
It looks like your data entities are in a separate assembly from your main application. The point of not instantiating the base is from a business point of view, so if you make the constructor internal to the Core assembly, does that accomplish what you want? If not, it may be helpful to ask yourself: who am I protecting this functionality from?
NHibernate should allow you to map the abstract class as a collection as long as you map the abstract class itself (it looks like you have).
An alternative is to change your strategy to the Table-per-class-hierachy approach. This puts all your content into a single table with a discriminator column to define the type of content. NHibernate knows how to materialize each content type based on the discriminator. The downside is that:
Each unique property of the concrete classes has to be of type nullable.
This table can get unwieldy if there are a lot of properties specific to each concrete class.
The table-per-class-hierachy is the preferred default mapping strategy (per NHibernate in Action). I would start with the approach and modify it to table-per-subclass when the need is certain.
A whole separate solution would be keep the mapping as is and rely on query to get the content by tag without worrying about the tags keeping a reference to a collection of content.
I'm using nHibernate to map an object very similar to .NET's System.Web.SiteMapNode. In order to keep my object similar to this .NET object I would like to have it contain a ParentNode, PreviousSibling, NextSibling, and ChildNodes complex properties.
The table looks somewhat like this and is open to be changed:
ID (int)
Title (string)
Description (string)
Key (string)
ParentNodeId (int)
OrdinalPosition (int)
ReadOnly (bool)
Url (string)
I may have some other properties that are not needed to mimic the .NET SiteMapNode object (like an isExternal bool), but I think those are inconsequential to this question.
My current mapping looks like this:
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="AthletesCafe.Core.Domain.System.SiteMap" assembly="AthletesCafe.Core">
<class name="SiteMapNode" table="SiteMapNode" lazy="true" >
<id name="ID" type="Int32" unsaved-value="0">
<column name="ID" not-null="true" unique="true" index="PK_SiteMapNode"/>
<generator class="identity" />
</id>
<property name="Title" column="Title" type="String" length="255" not-null="true" />
<property name="Description" column="Description" type="String" not-null="false" />
<property name="Url" column="Description" type="String" not-null="true" />
<property name="SiteMapKey" column="SiteMapKey" type="String" not-null="true" length="255" />
<property name="OrdinalPosition" column="OrdinalPosition" type="Int32" not-null="true" />
<property name="ReadOnly" column="ReadOnly" not-null="true" type="System.Boolean" />
<property name="IsExternal" column="IsExternal" not-null="true" type="System.Boolean" />
<many-to-one name="ParentNode" column="ParentNodeId" class="AthletesCafe.Core.Domain.System.SiteMap.SiteMapNode, AthletesCafe.Core"
access="field.pascalcase-underscore" not-null="false" />
<many-to-one name="PreviousNode" column="ParentNodeId" class="EatMyTrainer.Core.Domain.SiteMap.SiteMapNode, EatMyTrainer.Core" not-null="false" /></hibernate-mapping>
The ParentNode mapping is easy as it should be just a simple many-to-one mapping. This is the code I have for it (untested, but I believe it to be correct):
<many-to-one name="ParentNode" column="ParentNodeId" class="AthletesCafe.Core.Domain.System.SiteMap.SiteMapNode, AthletesCafe.Core"
access="field.pascalcase-underscore" not-null="false" />
The mapping for the child nodes should just be a simple bag which will bring back all SiteMapNode objects that have the ParentNodeId equal to the current ID. I haven't written this bag yet, but I believe it to be not such a big deal.
The issue that I cannot seem to resolve is how to do the Next/Previous Sibling properties. This objects can be derived from the following formula for each node:
PreviousSibling: Has the same ParentNode (ParentNodeId) as the current object and its OrdinalPosition should be one less than the current object's OrdinalPosition.
NextSibling: Has the same ParentNode (ParentNodeId) as the current object and its OrdinalPosition should be one more than the current object's OrdinalPosition.
I think this is achievable through the formual attribute on a many-to-one mapping. Is this possible? I haven't found a good example of how this works.
I don't think what you're asking for is strictly possible (although I would be very interested to see the solution if it is). There would be a relatively simple workaround, but NHibernate does not support bidirectional one-to-many mappings with indexed collections on the many end.
The only thing that comes to mind is a bit ugly: have the parent object keep its own index map (keyed off the OrdinalPosition) to each child object. On the child do something like:
public SiteMapNode NextSibling()
{
return this.Parent.NextSibling(this);
}
I believe Stuart is correct in this situation. It is impossible to do for the many-to-one mapping. If NHibernate provided a way to do where clausing on this mapping then I may have a chance.
Another possible solution although inefficient is to create a bag that uses a field setter. The public property that would be Next/Previous setting would still return an object reference (as opposed to an enumerable). In the getter it would just reference the first position of the enumerable in the field. Lazy loading would be ideal because NHibernate wouldn't be able to load this object in one get with the initial load of the object. You would have a penalty for accessing this object every time.
I guess both solutions have a similar penalty.