I'm trying to use an NHibernate filter to filter on a parent class's property, but I keep getting an error that the multi-part identifier "Parent.Active" could not be bound. My filter-def is:
<filter-def name="useActive" />
My parent class has this in the mapping:
<property name="Active">
<column name="ACTIVE" not-null="true" />
</property>
<bag name="Children" table="CHILDREN" inverse="true">
<key>
<column name="PARENT_ID_IN_CHILD" />
</key>
<one-to-many class="ChildType" />
</bag>
My child class has this in the mapping:
<many-to-one name="Parent" class="ParentTyle">
<column name="PARENT_ID_IN_CHILD" />
</many-to-one>
<filter name="useActive" condition="Parent.Active = 1" />
How can I get NHibernate to check the parent column when filtering?
edit: I'm enabling the filter using mySession.EnableFilter("useActive");. I'm also using LINQ-to-NHibernate, but I don't think that should matter.
The error you're receiving came from SQL Server that can't find the column "Active" on the table "Parent".
Keep in mind that when you're defining a filter the string that you put in the condition will simply be appended in the where condition of the select as is. If you want to filter for that field you must first identify the alias nHibernate use for your SQL query than put that alias instead of "Parent". it coube something like "mytable_0" or something like that.
Related
I'm working with NHibernate and QueryOver. I have an aggregate root for my aggregate named Parent and two kinds of child entity. I have Child entities that are parts of my aggregate, and QUChild entities that are not parts of my aggregate, and are just used for JOIN clause in QueryOver.
How to distinguish between two child entities in mapping file?
<class name="Parent" table="Parent" schema="dbo">
<bag name="Childs" inverse="true" cascade="all-delete-orphan" />
<key>
</key>
<one-to-many class="Child" />
</bag>
<bag name="QUChilds" /> <!-- which attribute must be set to do nothing? -->
<key>
</key>
<one-to-many class="QUChild" />
</bag>
</class>
Well, just do nothing with it. NHibernate will not eager load, nor lazy-load it if you do not access it from your loaded parent entities.
And default cascade is none, so just leave it as you have mapped it. (But I would add inverse="true" just in case code changes lead to add some children in that collection too, later on.)
It is possible to specify an arbitrary SQL where clause for collection mappings. For example:
<map name="myEntity" where="foo = 1" />
However if the column name is ambiguous for some reason, the sql fails. For example, this can occur if you are trying to use joins for example.
Given that the table aliases are automatically generated, you can't qualify the column name. This makes the feature seem rather silly. Does anyone know if there is a work around?
NHibernate should figure out the correct alias for the property you are referencing. Is foo a mapped property of the item entity type (the item type that is in the map collection) ?
For example this works:
<class name="Category" table="Category">
<id name="Id">
<generator class="guid.comb" />
</id>
<property name="Name" not-null="true" length="255" />
<bag name="ProductList" table="Product" cascade="none" where="Name like '%test%'" fetch="join">
<key column="CategoryId" />
<one-to-many class="Product" />
</bag>
</class>
There is a property on both Category and the Product class named "Name" but nhibernate will in this case use the on defined on the Product class.
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.
Mapping a dictionary with NH. Declaration is as follows:
<hibernate-mapping ...
<map
name="CostsByRole"
table="JobAccountingSnapshotCosts"
lazy="false"
fetch="join"
access="nosetter.camelcase-underscore">
<key column="SnapshotId" />
<index column="RoleCode" type="String" />
<element column="Amount" type="Decimal" />
</map>
</hibernate-mapping>
I am expecting a single SQL query to be generated but instead I get two: a select for the actual object, followed by a select for the contents of the dictionary.
Any ideas?
HQL queries do not consider the values set for fetch in the mapping. You need to specify them exclusively in each HQL query. Its supposedly by design. The fetch attributes value is used only by Criteria queries and by Load/Get.
Assuming it's not a typo on submission, the problem is likely to be the join="fetch" part in your mapping. It should be fetch="join" and since the default for fetch is "select", that would yield your sequential select problem.