we use an external Database where we cant edit table designs only add own tables to extend the core tables.
So I need map two tables on one class, i try this:
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
assembly="DaVinci"
namespace="DaVinci.Domain">
<class name="Vorgang" table="VORGANGSKOPF">
<id name="Id" column="ID">
<generator class="native" />
</id>
<property name="Vorgangsnummer" column="VORGANG" />
...
<join table="OWN_VORGANG_WAEHRUNG" optional="true">
<key column="VOR_ID" property-ref="Vorgangsnummer" />
<property name="WaehrungVK_Internet" column="WAEHRUNG" />
<property name="WaehrungsKursVK_Internet" column="KURS" />
<property name="Preis_Internet" column="BETRAG_EURO" />
<property name="PreisFremdWaehrung_Internet" column="BETRAG_FREMD" />
</join>
...
After testing i know now that "property-ref" for joins dosn't work.
Bugreport here
Does anyone know an other way to map two tables on one class?
(I'm struggling a little with the table and column names here.)
Could you use a joined subclass for this? Even if the tables don't follow the logical relationship, if there's a 1-to-1 database relationship between the two tables, then you'd get what you want by ignoring the parent, and doing all your operations on the subclass.
Related
I'm trying to map a self-referencing table with NHibernate 3.2.0.4000. However, whenever I get an instance of DomainObject, it eagerly loads the subsequent versions. I'd rather not have to put an extra column my table, though that is an option.
Can I have NHiberante not eagerly load all of the subsequent versions without maintaining the relationship on both sides?
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping assembly="NHibernateHierarchyTest" namespace="NHibernateHierarchyTest" xmlns="urn:nhibernate-mapping-2.2">
<class name="DomainObject" table="DOMAIN_OBJECT" lazy="true" >
<id name="DomainObjectId" column="DOMAIN_OBJECT_ID">
<generator class="identity" />
</id>
<property name="Property">
<column name="PROPERTY" />
</property>
<many-to-one name="PreviousVersion" class="DomainObject" >
<column name="PREVIOUS_VERSION_DOMAIN_OBJECT_ID" />
</many-to-one>
<!--<many-to-one name="SubsequentVersion" class="DomainObject">
<column name="SUBSEQUENT_VERSION_DOMAIN_OBJECT_ID" />
</many-to-one>-->
<one-to-one name="SubsequentVersion" class="DomainObject" property-ref="PreviousVersion" />
</class>
</hibernate-mapping>
The one-to-one mapping will be always loaded eagarly with NHibernate. Not sure if this is a feature or bug, but that is how it works. If you need lazy load, use many-to-one or one-to-many. Not the best answer I know, but if you can add new column...
I am having some troubles crafting the HQL for a given nHibernate mapping file (nHibernate 1.2). This SQL Fiddle example shows the table structures and the results I'm wanting. Basically, I'll pass in a Jurisdiction and I want all Titles with no jurisdiction or that specific jurisdiction. The current process pulls everything back and filters in code; I'm working to improve this so it filters at the SQL level.
Mapping file looks very similar to this.
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
assembly="MyApp.Business"
namespace="Ap.Bus.Entity"
default-access="field.camelcase-underscore"
default-cascade="save-update" >
<class name="Titles" table="dbo.Titles" mutable="true" lazy="true">
<!--Primary Key-->
<id column="TitleID" name="Id" unsaved-value="0">
<generator class="identity">
</generator>
</id>
<property column="TITLE" name="Title"/>
<property column="Enabled" name="Enabled" />
<bag name="Jurisdictions" table="dbo.Jurisdictions" lazy="false" cascade="none">
<key column="TitleID" />
<many-to-many class="Ap.Shared.Jurisdiction, Ap.Shared" column="JurisdictionID"/>
</bag>
</class>
I've tried so many different HQLs and I could never get it to work when I started joining to the Jurisdictions. It was working when only returning enabled Titles without the join.
So, how can I write the HQL to accomplish this?
select t
from Title t left outer join t.Jurisdictions as j
where j is null or j = :someJurisdiction
Possibly you should add ".JurisdictionID" to the last two "j" above.
I am working on an existing data structure that is not perfect and I have an inheritance mapping issue to solve.
I am using a table per hierarchy and have subclasses with discriminators set up. However the subclassed properties are foreign keys back to other tables. How do I set up my subclass mapping so that when I query the fk property I get an object rather than null? Is this even possible?
My current Mapping
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="MVC3" namespace="MVC3.Models">
<class name="Image" table="Images">
<id name="Id" column="ImageId">
<generator class="identity" />
</id>
<discriminator column="ImageType" />
<property name="Url" column="Url" not-null="true" />
<property name="Caption" column="Caption" />
<subclass name="AupairImage" discriminator-value="AupairImage">
<join table="Aupairs" inverse="true">
<key column="AupairId" />
<many-to-one name="Aupair" column="AupairId" class="Aupair" />
</join>
</subclass>
<subclass name="FamilyImage" discriminator-value="FamilyImage">
<join table="Families" inverse="true">
<key column="FamilyId" />
<many-to-one name="Family" column="FamilyId" class="Family" />
</join>
</subclass>
I would have like to add an entity diagram but I cannot post images yet :0(
But the foreign keys AupairId and FamilyId link off back to two other tables and are of the type int 32
I know it would be better to restructure the Aupair And Family entities to have a hierarchy to get rid of the one in images but this would be a last resort due to existing code.
Thanks in advance any help appreciated from you mapping experts....
Realised what I was doing wrong after taking a second look, should have just used a Many-To-One under the Subclass with a defined column
<subclass name="MVC3.Models.FamilyImage, MVC3" discriminator-value="FamilyImage">
<many-to-one cascade="all" class="MVC3.Models.Family, MVC3" name="Family">
<column name="FamilyId" />
</many-to-one>
</subclass>
Currently I have the following classes:
class Article with properties id, title and body
class Question : Article with an extra PostedBy property
Then I have a table called Article with the above properties and a table called questions with an ID a foreign key articleID and a PostedBy. Both are in different schemas
I would like to know how are my mappings going to look to represent this relation. Both classes are in different assemblies and i would be very reluctant to put Question logic in Article class/mapping and its assembly.
NHibernate supports three basic inheritance strategies.
table per class hierarchy
table per subclass
table per concrete class
It sounds like you are looking for the table per subclass strategy as you have a table for your Article class and another table for the extra properties on the Question subclass. The mapping might looks something like this:
<class name="Article" table="Article">
<id name="Id" type="Int64" column="ArticleId">
<generator class="native"/>
</id>
<property name="Title" column="Title"/>
<property name="Body" column="Body"/>
...
<joined-subclass name="Question" table="Question">
<key column="ArticleId"/>
<property name="PostedBy" column="PostedBy"/>
...
</joined-subclass>
</class>
However, this doesn't meet your desire to keep the mappings entirely separate. You could have entirely separate mappings, but this might have some side effects as allowing Question to be loaded as a plain Article instead of a Question. With separate mapping the Article class would be straight-forward as expected. The Question class would include a join to access the properties stored in the Article table.
<class name="Article" table="Article">
<id name="Id" type="Int64" column="ArticleId">
<generator class="native"/>
</id>
<property name="Title" column="Title"/>
<property name="Body" column="Body"/>
...
</class>
<class name="Question" table="Question">
<id name="Id" type="Int64" column="QuestionId">
<generator class="native"/>
</id>
<property name="PostedBy" column="PostedBy"/>
...
<join table="Article">
<key column="ArticleId"/>
<property name="Title" column="Title"/>
<property name="Body" column="Body"/>
</join>
</class>
We have a legacy database schema which I've tried (unsuccessfully) to map with NHibernate. To give a simplified example, say I want a Person class whose first name comes from the "Person" table, but their last name comes from the "Person2" table. The "Person" table also has the Id of the person's Car and I want my Person class to have a Car property. I can map all that using the following;
<hibernate-mapping default-cascade="save-update" xmlns="urn:nhibernate-mapping-2.2" auto-import="true">
<class name="NHibernateMappingTest.Person, NHibernateMappingTest" lazy="false">
<id name="Id" >
<generator class="native" />
</id>
<property name="FirstName" />
<many-to-one name="Car" access="property" class="NHibernateMappingTest.Car, NHibernateMappingTest" column="CarId" cascade="save-update"/>
<join table="Person2">
<key column="PersonId" />
<property name="LastName" />
</join>
</class>
</hibernate-mapping>
The lets me combine the Person and Person2 tables, and the lets me find their Car - everything works fine.
But... if the Person2 table happens to have the person's HouseId, I'd like to be able to add a second element to my mapping...
<many-to-one name="House" access="property" class="NHibernateMappingTest.House, NHibernateMappingTest" column="HouseId" cascade="save-update"/>
...so that my Person class can have a House property.
However this is where it all goes wrong, because the SQL which NHibernate generates assumes that the HouseId column is in the Person table (but it's not, it's in Person2), so I get the following error;
MySql.Data.MySqlClient.MySqlException: #42S22Unknown column 'HouseId' in 'field list'
Is NHibernate able to do what I'm attempting, is there a different way to achieve this (without changing the database schema), or have I just made a beginner's error in my map file?
Vincent - thanks for your response. No I wasn't nesting the tag element inside the element. But following your suggestion, I tried and it works perfectly! Thanks very much for responding.
<hibernate-mapping default-cascade="save-update" xmlns="urn:nhibernate-mapping-2.2" auto-import="true">
<class name="NHibernateMappingTest.Person, NHibernateMappingTest" lazy="false">
<id name="Id" >
<generator class="native" />
</id>
<property name="FirstName" />
<many-to-one name="Car" access="property" class="NHibernateMappingTest.Car, NHibernateMappingTest" column="CarId" cascade="save-update"/>
<join table="Person2">
<key column="PersonId" />
<property name="LastName" />
<many-to-one name="House" access="property" class="NHibernateMappingTest.House, NHibernateMappingTest" column="HouseId" cascade="save-update"/>
</join>
</class>
</hibernate-mapping>