Recently I came across a problem where I had to auto generate entity Id by using seed table of database. I was not allowed to keep auto generate at database level. I was using NHibernate ORM.
Scenario:
I have a seed table.
Table : Seed
Columns :
1. TableName
2. LastId
I have to use this table to create id for other tables. I was looking a better way to accomplish this.
I have to use this table to create id for other tables. I was looking a better way to accomplish this.
Solution :
1. Create a seed generator class - NHibernate gives an interface IIdentifierGenerator which really helps lot. It gives a signature to use and pass id.
namespace SimpleNHibernateClient.ConsoleApplication
{
using NHibernate.Id;
/// <summary>
/// Seed Generator
/// </summary>
public class SeedGenerator<T> : IIdentifierGenerator
{
public object Generate(NHibernate.Engine.ISessionImplementor session, object obj)
{
return 1;/* Take it from seed table corresponding T. */
}
}
}
2. Entity Class-This is a entity class to be saved into database.
namespace SimpleNHibernateClient.ConsoleApplication
{
public class Student
{
public virtual int Id { get; set; }
public virtual string Name { get; set; }
}
}
3. Mapping Class-This is a mapping class to be used for mapping and calling seed generator.
namespace SimpleNHibernateClient.ConsoleApplication
{
using FluentNHibernate.Mapping;
public class StudentMap : ClassMap<Student>
{
public StudentMap()
{
Table("Student");
Id(x => x.Id, "Id").GeneratedBy.Custom<SeedGenerator<Student>>();
Map(x => x.Name, "Name");
}
}
}
Now it gets generated by Generate Method.
