I'm using NHibernate 2.1.2 + Fluent NHibernate
I have a ContactInfo class and table. The Name column is encrypted in the database (SQL Server) using EncryptByPassphrase/DecryptByPassphrase.
The following are the relevant schema/class/mapping bits:
table ContactInfo(
int Id,
varbinary(108) Name)
public class ContactInfo
{
public virtual int Id { get; set; }
public virtual string Name { get; set; }
}
public class ContactInfoMap : ClassMap<ContactInfo>
{
public ContactInfoMap()
{
Id(x => x.Id);
Map(x => x.Name)
.Formula("Convert(nvarchar, DecryptByPassPhrase('passphrase', Name))");
}
}
Using the Formula approach as above, the values get read correctly from the database, but NHibernate doesn't try to insert/update the values when saving to the database (which makes sense).
The problem is that I would like to be able to write the Name value using the corresponding EncryptByPassPhrase function. I'm unsure if NHibernate supports this, and if it does, I haven't been able to find the correct words to search the documentation effectively for it.
So... how can I write this computed property back to the database with NHibernate?
Thanks in advance!
A property mapped to a formula is read-only.
A named query wrapped up in a ContactInfoNameUpdater service might be one way to solve the problem.
Related
I defined my entities with bunch of columns and created mapping.
public class PurchaseRecord {
public virtual int? Id {
get;
set;
}
public virtual DateTime? PurchasedDate {
get;
set;
}
public virtual string Comment {
get;
set;
}
public virtual IList<PurchaseRecordExtendedProperty> ExtendedPropertyValues {
get;
set;
}
public class PurchaseRecordMap : ClassMap<PurchaseRecord> {
public PurchaseRecordMap() {
Table("PurchaseRecords");
Id(x => x.Id, "RecordID").GeneratedBy.Identity();
Map(x => x.PurchasedDate, "PurchaseDate").Not.Nullable();
Map(x => x.Comment, "Comment");
HasMany(x => x.ExtendedPropertyValues).KeyColumn("ExtendedPropertyID").Cascade.All();
}
It works well in most of the cases, howerver in some certain situation I want to skip updating certain column (such as child collection ExtendedPropertyValues). When I create the PurchaseRecord object I don't even bother to load the data of ExtendedPropertyValues. But if the property is null NHibernate tries to delete the child records from database.
I know there are some scenario that the ExtendedPropertyValues will never be changed. For performance consideration I don't want to load the data I don't need, is there a way I can force NH to skip designated properties if I don't need to update?
Thanks for any suggestion.
If you enable lazy loading, NHibernate will not try to load any child collections, they will be initialized to a proxy which will only load them if you access them. If you set the child collection to null, that is effectively telling NHibernate to delete all entries in that relationship (unless you mark the relationship as inverse).
NHibernate will not try to update the child collections unless they change (which setting it to null would do).
In summary, enable lazy-loading, and mark ExtendedPropertyValues as inverse, and it should not update it unless you change ExtendedPropertyValues, it also will not load ExtendedPropertyValues unless you access it.
I'm trying to set up a relationship as follows. Each Master item has one or more Detail items:
public class Detail {
public virtual Guid DetailId { get; set; }
public virtual string Name { get; set; }
}
public class Master {
public virtual Guid MasterId { get; set; }
public virtual string Name { get; set; }
public virtual IList<Detail> Details { get; set; }
}
And Mappings:
public class MasterMap : ClassMap<Master>
{
public MasterMap()
{
Id(x => x.MasterId);
Map(x => x.Name);
HasMany(x => x.Details).Not.KeyNullable.Cascade.All();
}
}
public class DetailMap : ClassMap<Detail>
{
public DetailMap()
{
Id(x => x.Id);
Map(x => x.Name);
}
}
The Master database table is:
masterId uniqueidentifier NOT NULL
name nvarchar(max) NULL
and Detail is:
DetailId uniqueidentifier NOT NULL
name nvarchar(max) NULL
MasterId uniqueidentifier NULL
foreign key (masterId) references [Master]
I don't really care to have a link from Detail back to Master -- in otherwords, Detail objects on their own are just not interesting to my domain layer. They will always be accessed via their Master object.
Using code like this:
Master mast = new Master
{
MasterId = new Guid(),
Name = "test",
Details = new List<Detail>
{
new Detail { .DetailId = new Guid(), .Name = "Test1" },
new Detail { .DetailId = new Guid(), .Name = "Test1" }
}
};
using (transaction == Session.BeginTransaction)
{
Session.Save(mast);
transaction.Commit();
}
This works great, except for a crazy limitation outlined in this post: NHibernate does an INSERT and puts Detail.MasterId as NULL first, then does an UPDATE to set it to the real MasterId.
Really, I don't want Detail entries with NULL MasterIds, so if I set the MasterId field to NOT NULL, the INSERT to Detail will fail, because as I said NHibernate is trying to put in MasterId = NULL.
I guess my question boils down to this:
How can I get the above code sample to work with my existing domain model (eg, without adding a Detail.Master property), and the Detail.MasterId field in the database set to NOT NULL?
Is there a way to get Nhibernate to just put the correct MasterId in the initial INSERT, rather than running an UPDATE afterwards? Is there rationale somewhere for this design decision? -- I'm struggling to see why it would be done this way.
NH3 and above allow to correct save entities in case of uni-directional one-to-many mapping without annoying save null-save-update cycle, if you set both not-null="true" on <key> and inverse="false" on <one-to-many>
FluentNHibernate code snippet for that:
public class MasterMap : ClassMap<Master>
{
public MasterMap()
{
Id(x => x.MasterId);
Map(x => x.Name);
HasMany(x => x.Details)
.Not.Inverse() //these options are very
.Not.KeyNullable() //important and work only if set together
.Not.KeyUpdate() //to prevent double update
.Cascade.All();
}
}
You can't. To quote the link from my answer on the other question you linked to:
Very Important Note: If the <key> column of a <one-to-many> association is declared NOT NULL, NHibernate may cause constraint violations when it creates or updates the association. To prevent this problem, you must use a bidirectional association with the many valued end (the set or bag) marked as inverse="true". See the discussion of bidirectional associations later in this chapter.
Edit: as Hazzik has rightly pointed out, this has changed in NHibernate 3 and above. The docs sadly haven't been updated, so here's Hazzik:
[If you] set inverse="false" and not-null on <key>, NH3 and above will perform only two inserts insead of insert-insert-update.
The reason NHibernate does it this way is because:
When it saves the detail it only knows about the stuff the detail knows about. So any master references which happen in the background are ignored.
Only when the master is saved it sees the relation and updates the elements of the collection with the id of the master.
Which is from an object oriented point of view logical. However from a saving point-of-view is slightly less logical. I suppose you can always file a bug report, or look if it might have been filed already and ask them to change it. But I suppose they have their specific (design/domain) reasons.
I have a class which I would like to map as a component onto any table which contains it:
public class Time
{
public int Hours { get; set; }
public int Minutes { get; set; }
public int Seconds { get; set; }
}
I would like to store this class as a bigint in the database - the same as how TimeSpan is stored but my class has completely different behaviour so I decided to create my own.
I'm using FLH's automapper and have this class set as a component (other classes have Time as a property). I've got as far as creating an override but am not sure how to go about mapping it:
I gave it a try this way:
public class TimeMappingOverride : IAutoMappingOverride<Time>
{
public void Override(AutoMapping<Time> mapping)
{
mapping.Map(x => x.ToTimeSpan());
mapping.IgnoreProperty(x => x.Hours);
mapping.IgnoreProperty(x => x.Minutes);
mapping.IgnoreProperty(x => x.Seconds);
}
}
But got this error:
Unable to cast object of type 'System.Linq.Expressions.UnaryExpression' to type 'System.Linq.Expressions.MethodCallExpression'.
How should I go about this?
Details of components can be found here: http://wiki.fluentnhibernate.org/Fluent_mapping#Components
But first of all, you can't map a method.
Assuming you change ToTimeSpan() to a property AsTimeSpan, there are two ways to do it, only the harder of which will work for you because you are using automapping:
Create a ComponentMap<Time> -- once done, your existing mapping will just work. This is not compatible with automapping.
Declare the component mapping inline:
mapping.Component(x => x.AsTimeSpan, component => {
component.Map(Hours);
component.Map(Minutes);
component.Map(Seconds);
});
You'll have to do this every time, though.
Of course, this doesn't address "I would like to store this class as bigint…"
Are you saying you want to persist it as seconds only? If so, scratch everything at the top and again you have two options:
Implement NHibernate IUserType (ugh)
Create a private property or field that stores the value as seconds only, and wire only this up to NHibernate. The getters and setters of the pubic properties will have to convert to/from seconds.
I personally haven't worked with AutoMappings yet, but my suggestion would be to look into NHibernate's IUserType to change how a type is being persisted. I believe that's a cleaner way of defining your custom mapping of Time <-> bigint.
Reading the code above, Map(x => x.ToTimeSpan()) will not work as you cannot embed application-to-database transformation code into your mappings. Even if that would be possible, the declaration misses the transformation from the database to the application. A IUserType, on the other hand, can do custom transformations in the NullSafeGet and NullSafeSet methods.
I have the following (simplified)
public enum Level
{
Bronze,
Silver,
Gold
}
public class Member
{
public virtual Level MembershipLevel { get; set; }
}
public class MemberMap : ClassMap<Member>
{
Map(x => x.MembershipLevel);
}
This creates a table with a column called MembershipLevel with the value as the Enum string value.
What I want is for the entire Enum to be created as a lookup table, with the Member table referencing this with the integer value as the FK.
Also, I want to do this without altering my model.
To map an enum property as an int column, use method CustomType.
public class MemberMap : ClassMap<Member>
{
Map( x => x.MembershipLevel ).CustomType<int>();
}
In order to keep the enum and lookup table in sync, I would add the lookup table and data to your sql scripts. An integration test can verify that the enum and lookup table values are the same.
If you wanted SchemaExport to create this table, add a class and mapping for it.
public class MembershipLevel
{
public virtual int Id { get; set; }
public virtual string Code { get; set; }
}
public class MembershipLevelMap : ClassMap<MembershipLevel>
{
Id( x => x.Id );
Map( x => x.Code );
}
If you are creating the table with SchemaExport, you will need to populate it as well:
foreach (Level l in Enum.GetValues( typeof( Level ))) {
session.Save( new MembershipLevel{ Id = (int) l, Code = l.ToString() });
}
I wouldn't do that because your Enum declaration is not dynamic, or simpler, it doesn't change without recompiling, while your lookup table may change at any moment. If the Enum's and lookup table's values don't match, what's next?
Another reason is if you change the Enum (in code), you'd have to synchronise it with the database table. Since Enums don't have an incremental key (PK), they can't be synchronised so simple. Let's say you remove one Enum member from your code and recompile it, what is supposed to happen? And if you change a value?
I hope I made my objections to this approach clear. So I strongly recommend storing the name or the value of your enum members. To store it by name, just map like this:
public class MemberMap : ClassMap<Member>
{
Map(x => x.MembershipLevel, "level")
.CustomType<GenericEnumMapper<Level>>()
.Not.Nullable();
}
To store the values, do as #Lachlan posted in his answer.
Or if you really need a lookup table and wants to use an Enum with strict checking, create a normal model with PK (or use value for this), KEY and VALUE. Create your enum with your static members, and make the application query the database for the names and values when you start it. If things don't match, do whatever you need. Additionally, this doesn't guarantee your table won't change while your program is running, so you better be sure it doesn't.
I have a class called Entry. This class as a collection of strings called TopicsOfInterest. In my database, TopicsOfInterest is represented by a separate table since it is there is a one-to-many relationship between entries and their topics of interest. I'd like to use nhibernate to populate this collection, but since the table stores very little (only an entry id and a string), I was hoping I could somehow bypass the creation of a class to represent it and all that goes with (mappings, configuration, etc..)
Is this possible, and if so, how? I'm using Fluent Nhibernate, so something specific to that would be even more helpful.
public class Entry
{
private readonly IList<string> topicsOfInterest;
public Entry()
{
topicsOfInterest = new List<string>();
}
public virtual int Id { get; set; }
public virtual IEnumerable<string> TopicsOfInterest
{
get { return topicsOfInterest; }
}
}
public class EntryMapping : ClassMap<Entry>
{
public EntryMapping()
{
Id(entry => entry.Id);
HasMany(entry => entry.TopicsOfInterest)
.Table("TableName")
.AsList()
.Element("ColumnName")
.Cascade.All()
.Access.CamelCaseField();
}
}
I had a similar requirement to map a collection of floats.
I'm using Automapping to generate my entire relational model - you imply that you already have some tables, so this may not apply, unless you choose to switch to an Automapping approach.
Turns out that NHibernate will NOT Automap collections of basic types - you need an override.
See my answer to my own question How do you automap List or float[] with Fluent NHibernate?.
I've provided a lot of sample code - you should be able to substitute "string" for "float", and get it working. Note the gotchas in the explanatory text.