I have the following class:
public class Foo
{
//...
protected int? someData;
public int? SomeData
{
get {return someData;}
set {someData = value;}
}
//...
}
This class is mapped in HBM file:
<class name="Foo" table="Foo">
//....
<property name="someData" access="field" column="SOME_DATA" />
//....
</class>
For legacy reasons, the columns were mapped to a fields (lowercase), which are unaccessible (not public properties - uppercase).
These lowercase mappings are using multiple times in the project as part of HQL strings, criteria-based queries and so on. It is close to impossible to find all usages.
The problem is that such usage makes it impossible to use even on simple lambda:
session.Query<Foo>().Select(f=>f.SomeData)
throws error, as uppercase "SomeData" is not mapped, and
session.Query<Foo>().Select(f=>f.someData)
does not compile, as lowercase "someData" is protected.
What happens, if I will map BOTH field and property:
<property name="someData" access="field" column="SOME_DATA" />
<property name="SomeData" access="property" column="SOME_DATA" />
I tried quickly, and it seems to work, but will it have any drawback?
Is there any other simple solution, that will not require editing every criteria-based query in project?
Thanks for any help.
You can map the same column multiple times but with recent NHibernate versions only one of the properties need to be mapped as modifiable. So just add insert="false" update="false" to your additional mappings to avoid any issues in future:
<property name="someData" access="field" column="SOME_DATA" />
<property name="SomeData" access="property" column="SOME_DATA" update="false" insert="false" />
Related
I need to retrieve all the users with a valid Wish property (so not null). This is the xml of my class:
<class name="Project.Engine.Domain.User,Project.Engine" table="Users" lazy="true">
<id name="UserID" column="UserID">
<generator class="native" />
</id>
<property name="Firstname" column="Firstname" type="string" not-null="true"
length="255" />
<property name="Lastname" column="Lastname" type="string" not-null="true"
length="255" />
<property name="Email" column="Email" type="string" not-null="true"
length="255" />
<one-to-one name="Wish" cascade="all" property-ref="UserID"
class="Project.Engine.Domain.Wish, Project.Engine" />
</class>
The method to get all my users is the following:
public PagedList<User> GetAll(int pageIndex, int pageSize,
string orderBy, string orderByAscOrDesc)
{
using (ISession session = NHibernateHelper.OpenSession())
{
var users = session.CreateCriteria(typeof(User));
users.Add(Restrictions.IsNotNull("Wish"));
return users.PagedList<User>(session, pageIndex, pageSize);
}
}
As you can notice, I have added the Restriction on the child object. This doesn't work properly as the method return all users including the ones with Wish property as null. Any help?
this is the xml for child:
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="Project.Engine.Domain.Wish,Project.Engine" table="Wish" lazy="false">
<id name="WishID" column="WishID">
<generator class="native" />
</id>
<property name="UserID" column="UserID" type="int" not-null="true" length="32" />
<property name="ContentText" column="ContentText" type="string" not-null="false" length="500" />
<property name="Views" column="Views" type="int" not-null="true" length="32" />
<property name="DateEntry" column="DateEntry" type="datetime" not-null="true" />
</class>
</hibernate-mapping>
Well, there is a bug with one-to-one and null testing of the side which may not exist. I had already encountered it but forgot about it. The property-ref just render it a bit more tricky to diagnose, but it does exist on actual one-to-one too.
Here is its corresponding issue in NHibernate tracking tool.
Workaround: test for null state of an non-nullable property of Wish, like Wish.Views.
Forgive the wild guess on test syntax, I do not use nhibernate-criteria anymore since years, but try by example:
public PagedList<User> GetAll(int pageIndex, int pageSize,
string orderBy, string orderByAscOrDesc)
{
using (ISession session = NHibernateHelper.OpenSession())
{
var users = session.CreateCriteria(typeof(User));
users.Add(Restrictions.IsNotNull("Wish.Views"));
return users.PagedList<User>(session, pageIndex, pageSize);
}
}
Using linq-to-nhibernate, I confirm this workaround works with my own projects, which gives by example:
// The "TotalAmount != null" seems to never be able to come false from a
// .Net run-time view, but converted to SQL, yes it can, if TransactionRecord
// does not exist.
// Beware, we may try "o.TransactionsRecord != null", but you would get struck
// by https://nhibernate.jira.com/browse/NH-3117 bug.
return q.Where(o => o.TransactionsRecord.TotalAmount != null);
I maintain my other answer since you may consider using a many-to-one instead, especially since you do not have made a bidirectionnal mapping (no corresponding constrained one-to-one in Wish) in addition to not having an actual one-to-one. many-to-one does not suffer of the bug.
one-to-one mapping using property-ref is not an "actual" one-to-one, and usually this is a sign a many-to-one mapping should be used instead.
Maybe this is not related to your trouble, but you may give it a try.
An "actual" one-to-one has the dependent table primary key equals to the parent table primary key. (Dependent table, Wish in your case, would have a foreign primary key, UserId in your case. See this example.)
I have sometime "played" with 'one-to-one property-ref', and I always ended giving it up due to many issues. I replaced that with more classical mappings, either changing my db for having an actual one-to-one, or using a many-to-one and living with a collection on child side though it would always contain a single element.
I am working with a brownfield database and am trying to configure a subclass map which joins to its subclasses with a column other than that of the specified id. The login table has a primary key column login_sk which I'd like to use as its id. It joins to two tables via a login_cust_id column (to make things more fun the corresponding columns in the adjoining tables are named differently). If I setup login_cust_id as the id of the UserMap it joins to its subclasses as expected. For what I hope are obvious reasons I do not want to use login_cust_id as the id for my User objects.
public class UserMap : ClassMap<IUser>
{
public UserMap()
{
Table("login");
Id(x => x.Id).Column("login_sk"); // want to setup map like this
// if used instead this works for subclass joining / mapping
// Id(x => x.Id).Column("login_cust_id");
// would prefer to only reference login_cust_id for subclass mapping
}
}
public class CustomerUserMap : SubclassMap<CustomerUser>
{
public CustomerUserMap()
{
Table("customer");
Map(c => c.DisplayName, "cust_mail_name");
Map(c => c.RecordChangeName, "cust_lookup_name");
KeyColumn("cust_id");
}
}
public class EntityUserMap : SubclassMap<EntityUser>
{
public EntityUserMap()
{
Table("entity");
Map(c => c.DisplayName, "entity_name");
KeyColumn("entity_id");
}
}
What I'd like to do is only use the login_cust_id column when joining to subclasses. Is there a fluent mapping setting that allows me to specify this? If not a fluent mapping is there a regular NHibernate XML mapping that would work? I'd prefer to not even map the column and only use it for joining if possible. If it helps there is a potential discriminator column login_holder_type which indicates which table to join to.
It did occur to me to setup an IClassConvention but after poking at the passed IClassInstance I could not determine any settings which would help me.
public class UserIdConvention : IClassConvention, IClassConventionAcceptance
{
public void Apply(IClassInstance instance)
{
// do something awesome with instance.Subclasses to
// specify the use of login_cust_id for subclass joining...
}
public void Accept(IAcceptanceCriteria<IClassInspector> criteria)
{
criteria.Expect(x => typeof(User).Equals(x.EntityType));
}
}
The lack of a populated Subclasses collection for the passed instance caused me to look for a more specific inspector which IParentInspector appears to be. Unfortunately Fluent NHibernate does not appear to have corresponding implementations for IParentInstance, IParentConvention or IParentConventionAcceptance like it does for IJoinedSubclassInspector. While I could probably implement my own before I do I wanted to ensure I wasn't barking up the wrong tree.
Is this sort of subclass id adjustment even possible? Am I missing something obvious in either my map or the Fluent NHibernate Conventions namespace? How can I map to a joined subclass with a different column/property than the id of parent?
I was able to think of three possible solution to your problem please see my findings below.
Solution 1: Discriminator based mapping with Join
My initial idea was to use a discriminator based mapping for modelling the inheritance, with each sub-class containing a join with a property ref, i.e
<class name="IUser" abstract="true" table="login">
<id name="Id" column="login_sk">
<generator class="identity"/>
</id>
<discriminator column="login_holder_type" not-null="true" type="System.String"/>
<subclass name="CustomerUser" discriminator-value="Customer">
<join table="customer" >
<key column="cust_id" property-ref="login_cust_id" />
<property name="DisplayName" column="cust_mail_name"/>
<property name="RecordChangeName" column="cust_lookup_name" />
</join>
</subclass>
<subclass name="EntityUser" discriminator-value="Entity">
<join table="entity" >
<key column="entity_id" property-ref="login_cust_id" />
<property name="CompanyName"/>
</join>
</subclass>
</class>
Unfortunately at this time this feature is supported in Hibernate but not in NHibernate. Please see here and here for the outstanding tickets. Some work has gone towards adding this feature which can be seen on this fork on github.
Solution 2: Discriminator based mapping with Many-to-One
Another option is to still use the discriminator based mapping, but use a many-to-one mapping within each of the sub-classes, which would allow you to join on the foreign key using a property-ref. This has the disadvantage of requiring separate classes for all of the properties in your customer and entity tables but is a workable solution.
<class name="IUser" abstract="true" table="login">
<id name="Id" column="login_sk">
<generator class="identity"/>
</id>
<discriminator column="login_holder_type" not-null="true" type="System.String"/>
<subclass name="CustomerUser" discriminator-value="Customer">
<many-to-one name="CustomerProps" property-ref="login_cust_id" />
</subclass>
<subclass name="EntityUser" discriminator-value="entity">
<many-to-one name="EntityProps" property-ref="login_cust_id" />
</subclass>
</class>
<class name="CustomerProps" Table="customer" >
<id name="Id" column="cust_id">
<generator class="assigned"/>
</id>
<property name="DisplayName" column="cust_mail_name"/>
<property name="RecordChangeName" column="cust_lookup_name" />
</class>
<class name="EntityProps" Table="entity" >
<id name="Id" column="entity_id">
<generator class="assigned"/>
</id>
<property name="CompanyName"/>
</class>
Solution 3: Discriminator based mapping with Joins to Updatable Views
The final option is to create an Updatable View in the DB for the customer and entity tables which contains the login_sk field. You can then use Join within each sub-class as you wouldn't require the property-ref.
<class name="IUser" abstract="true" table="login">
<id name="Id" column="login_sk">
<generator class="identity"/>
</id>
<discriminator column="login_holder_type" not-null="true" type="System.String"/>
<subclass name="CustomerUser" discriminator-value="Customer">
<join table="customerView" >
<key column="login_sk" />
<property name="DisplayName" column="cust_mail_name"/>
<property name="RecordChangeName" column="cust_lookup_name" />
</join>
</subclass>
<subclass name="EntityUser" discriminator-value="Entity">
<join table="entityView" >
<key column="login_sk" />
<property name="CompanyName"/>
</join>
</subclass>
</class>
I'm wondering how to best implement a property (here, LatestRequest) which is read-only, backed by a query.
Here, I have an Export, which can be requested to happen multiple times. I'd like to have a property on the Export to get the latest ExportRequest. At the moment, I've got a many-to-one mapping with a formula, like this:
<class name="Export" table="Exports">
<id name="Id">
<generator class="guid" />
</id>
<property name="Name" />
<bag name="Requests" cascade="all,delete-orphan" inverse="true" access="field.camelcase" order-by="CreationDate desc">
<key column="ExportId"/>
<one-to-many class="ExportRequest"/>
</bag>
<many-to-one name="LatestRequest"
class="ExportRequest"
formula="(select top 1 ExportRequests.Id from ExportRequests order by ExportRequests.CreationDate desc)"/>
</class>
<class name="ExportRequest" table="ExportRequests">
<id name="Id">
<generator class="native" />
</id>
<many-to-one name="Export"
class="Export"
column="ExportId"
not-null="true" />
<property name="CreationDate" />
<property name="Tag" />
</class>
However, since the ExportRequests.Id for LatestRequest is fetched when the Export is fetched, this access pattern returns stale data:
var export = session.Get<Export>(exportId);
export.AddRequest(new ExportRequest(DateTime.Now, "Foo"));
Assert.AreEqual("Foo", export.LatestRequest.Tag); // fails due to stale data
session.Update(export);
So, what's the best way to implement the LatestRequest property?
I could change the getter for LatestRequest so that it executes a Find query, which should be up to date, but I'm not sure how to make the Export aware of the session.
There are several ways to solve this. I would probably not try to make it "automatic" this way. To enhance performance and simplicity, I would just make it a normal reference and manage it in the business logic or the entity like this:
class Export
{
private IList<ExportRequest> requests;
ExportRequest LatestRequest { get; private set; }
public void AddRequest (ExportRequest request)
{
requests.Add(request);
LatestRequest = request;
}
}
So you don't need any special mappings nor any additional queries to get the latest request. And, most importantly, the entity is consistent in memory and does not depend on the persistency.
However you solve it, it is very important that the entity and the business logic is managing the data (in memory). It should be "persistence ignorant". The database and the data access layer are not responsible to manage relations and logic of the entities.
I am trying to create a table-per-hierarchy mapping using NHibernate 2.0.1.
I have a base class with properties that exist for each subclass that other classes inherit from. All of these objects are persisted to one table called Messages that contain all of the possible fields for each class. There is a SourceID which is the discriminator and should indicate which Poco to return for each subclass. Here is my current mapping.
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
assembly="NS.Core"
namespace="NS.Core.Model">
<class name="BaseMessage" table="Messages">
<id name="MessageID" type="Int64">
<column name="MessageID" />
<generator class="native" />
</id>
<discriminator column="SourceID" type="Int32"/>
<property name="DateCreated" access="property" column="DateCreated" type="DateTime" not-null="true"/>
<property name="DatePublished" access="property" column="DatePublished" type="DateTime"/>
<property name="SourceID" access="property" column="SourceID" type="Int32"/>
<many-to-one name="User" column="UserID" access="property" cascade="none" lazy="false" fetch="join" outer-join="true" />
<subclass name="NMessage" discriminator-value="0">
<property name="Body" access="property" column="Body" type="String"/>
</subclass>
<subclass name="BMessage" discriminator-value="1">
<property name="Title" access="property" column="Title" type="String"/>
<property name="Body" access="property" column="Body" type="String"/>
</subclass>
<subclass name="CMessage" discriminator-value="2">
<property name="Url" access="property" column="Url" type="String"/>
<property name="Body" access="property" column="Body" type="String"/>
</subclass>
</class>
</hibernate-mapping>
I get an error querying saying Could not format discriminator value to SQL string of entity NS.Core.Model.BaseMessage so I put a discriminator value on this class too althout it should never return the base class. That led me to some antlr errors.
Am I taking the wrong approach to this problem? I would like to query the table and get back a list of different POCOs that all inherit from the base class. It would never return the base class itself.
below is the BaseMessage.cs
using System;
using System.Collections.Generic;
using System.Runtime.Serialization;
using System.Text;
namespace NS.Core.Model
{
[Serializable]
[DataContract]
[KnownType(typeof(User))]
public class BaseMessage
{
#region Private variables
private long _messageID;
private DateTime? _dateCreated;
private DateTime? _datePublished;
private int _sourceID;
private User _user = new User();
#endregion
#region Properties
[DataMember]
public virtual long MessageID
{
get { return _messageID; }
set { this._messageID = value; }
}
[DataMember]
public virtual DateTime? DateCreated
{
get { return _dateCreated; }
set { this._dateCreated = value; }
}
[DataMember]
public virtual DateTime? DatePublished
{
get { return _datePublished; }
set { this._datePublished = value; }
}
[DataMember]
public virtual int SourceID
{
get { return _sourceID; }
set { this._sourceID = value; }
}
[DataMember]
public virtual User User
{
get
{
if (this._user != null)
{ return this._user; }
else { return new User(); }
}
set { this._user = value; }
}
#endregion
}
}
The approach is sound. I have done exactly this several times.
You could make it explicit in your code my having BaseMessage's default constructor be protected.
You need to declare a discriminator-value on the base class as well.
I favor string values for discriminators, as this clearer when performing SQL queries or reports. Also, since instances of BaseMessage shoudl not exist, in would use null for its discriminator value.
<class name="BaseMessage" table="Messages" discriminator-value="null">
<id />
<discriminator column="SourceID" />
<subclass name="NMessage" discriminator-value="NMessage">
</subclass>
<subclass name="BMessage" discriminator-value="BMessage">
</subclass>
<subclass name="CMessage" discriminator-value="CMessage">
</subclass>
</class>
Also, I see that you have mapped a property to the discriminator column. You should instead have a method that returns something unique to the class - in this case the code.
Note that you cannot change the class of a mapped entity after it has been saved. Not even by changing the discriminator. If you did change it via SQL, your 2nd level cache will still hold a version with the original class.
class BaseMessage
{
public virtual string MessageType { return null; }
}
class NMessage : BaseMessage
{
public override string MessageType { return "NMessage"; }
}
Finally, your mapping file is overly verbose as it includes values which are the default. The following attributes and elements can be removed:
access="property" - this is the default
type="String" - all the types you use can be inferred from your .NET class
column="COL" - default is the same as the name
similarly for the id column element
All of your Message subclasses have property Body, so move it to the base class mapping. If this field can be longer than your database varchar, it should be a text column and have type="StringCLob" which maps to string in .NET
<class name="BaseMessage" table="Messages" discriminator-value="null">
<id name="MessageID">
<generator class="native" />
</id>
<discriminator column="SourceID"/>
<property name="DateCreated" />
<property name="DatePublished" />
<many-to-one name="User" column="UserID" cascade="none" lazy="false" fetch="join" outer-join="true" />
<property name="Body" type="StringCLob" />
<subclass name="NMessage" discriminator-value="NMessage">
</subclass>
<subclass name="BMessage" discriminator-value="BMessage">
<property name="Title" />
</subclass>
<subclass name="CMessage" discriminator-value="CMessage">
<property name="Url" />
</subclass>
</class>
I have a class StoreHours that has a composite key and has been working perfectly. A new demand came up for another type of hours to be returned. I thought "simple, I'll abstract the base class, have two concrete implementations and change my references in the app to one of the new classes". However, upon doing that, my unit tests failed with
X.Test.StoreTest.HoursTest: NHibernate.InstantiationException : Cannot instantiate abstract class or interface: X.Model.StoreHours
My mapping file looks like
<class name="StoreHours" table="StoreHour" abstract="true" discriminator-value="0" >
<composite-id>
<key-many-to-one name="Store"
class="Store"
column="StoreUid"/>
<key-property name="DayOfWeek"
column="DayOfWeekId"
type="System.DayOfWeek" />
</composite-id>
<discriminator column="StoreHourType" type="Byte" />
<property name="OpenMinutes" column="OpenTime" />
<property name="CloseMinutes" column="CloseTime" />
<subclass name="OfficeHours" discriminator-value="1" />
<subclass name="AccessHours" discriminator-value="2" />
</class>
I found someone with similar troubles here and started down their solution path but actually ended up with even more troubles than I started with.
I can persist the records to the database perfectly but onload, NHibernate is trying to instantiate the abstract 'StoreHours' even though I've only got a strongly type set off 'OfficeHours'
This seems like a really trivial requirement so I figure I must be doing something simple wrong. All hints appreciated.
The problem is in the way you are using the composite-id
Table-per-class works with Composite-id, but only if the composite is
implemented as a class
so you need to create a class like
public class StoreHoursCompositeId
{
public virtual Store Store { get; set; }
public virtual DayOfWeek DayOfWeek { get; set; }
// Implement GetHashCode(), is NH-mandatory
// Implement Equals(object obj), is NH-mandatory
}
In your StoreHours object create a property which use the above class (in my example I called it "StoreHoursCompositeId")
Your mapping become:
<class name="StoreHours" table="StoreHour" abstract="true" discriminator-value="0" >
<composite-id name="StoreHoursCompositeId" class="StoreHoursCompositeId">
<key-many-to-one name="Store" class="Store"
column="StoreUid"/>
<key-property name="DayOfWeek"
column="DayOfWeekId"
type="System.DayOfWeek" />
</composite-id>
<discriminator column="StoreHourType" type="Byte" />
<property name="OpenMinutes" column="OpenTime" />
<property name="CloseMinutes" column="CloseTime" />
<subclass name="OfficeHours" discriminator-value="1" />
<subclass name="AccessHours" discriminator-value="2" />
</class>
I had the very same problem and this fixed it for me.