NHibernate - Override Configuration

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In this chapter, we will be covering how to override NHibernate configuration. There are just a few things you need to keep in mind.

  • First of all, configuration in NHibernate is additive.

  • So you don't just have to use a single xml file or you don't just have to use the code-based configuration or fluent NHibernate.

  • You can mix and match all of these methods depending on how you want to configure your application.

  • The important point to remember is that, lastly configuration wins.

In the following example, you can see that we create our configuration object, configure it using the code-based configuration and finally call the cfg.configure() method, which loads the hibernate.cfg.xml file.

String Data Source = asia13797\\sqlexpress;
String Initial Catalog = NHibernateDemoDB;
String Integrated Security = True;
String Connect Timeout = 15;
String Encrypt = False;
String TrustServerCertificate = False;
String ApplicationIntent = ReadWrite;
String MultiSubnetFailover = False;

cfg.DataBaseIntegration(x = > { x.ConnectionString = "Data Source + 
   Initial Catalog + Integrated Security + Connect Timeout + Encrypt +
   TrustServerCertificate + ApplicationIntent + MultiSubnetFailover"; 
	
   x.Driver<SqlClientDriver>(); 
   x.Dialect<MsSql2008Dialect>(); 
   x.LogSqlInConsole = true; 
}); 

cfg.Configure();

  • So anything inside of a hibernate.cfg.xml overrides the settings set by code-based configuration.

  • By reversing these two processes we can have the defaults inside of hibernate.cfg.xml and then do our overrides inside of a code-based configuration.

  • There is nothing that excludes if you are using code-based configuration and also there is nothing that prevents you from using the hibernate.cfg.xml file.

Let’s have a look into a simple example in which we will override the configuration by using a mixture of xml-based and code-based configuration.

Let’s also move the connection string to the app.config file using the following code.

<?xml version = "1.0" encoding = "utf-8" ?> 

<configuration> 
   
   <startup> 
      <supportedRuntime version = "v4.0" sku = ".NETFramework,Version = v4.5" /> 
   </startup> 
   
   <connectionStrings> 
      <add name = "default" connectionString = "Data Source =
         asia13797\\sqlexpress;
         Initial Catalog = NHibernateDemoDB;
         Integrated Security = True;
         Connect Timeout = 15;
         Encrypt = False;
         TrustServerCertificate = False;
         ApplicationIntent = ReadWrite;
         MultiSubnetFailover = False"/> 
   </connectionStrings> 

</configuration>

The connection string is sitting in some app.config file with a default name. Now, we need to mention the default name in hibernate.cfg.xml file instead of the connection string.

<?xml version = "1.0" encoding = "utf-8" ?> 
<hibernate-configuration xmlns = "urn:nhibernate-configuration-2.2"> 

   <session-factory> 
      <property name = "connection.connection_string">default</property> 
		
      <property name = "connection.driver_class">
         NHibernate.Driver.SqlClientDriver
      </property> 
		
      <property name = "dialect">
         NHibernate.Dialect.MsSql2008Dialect
      </property> 
		
      <mapping assembly = "NHibernateDemoApp"/> 
   </session-factory> 

</hibernate-configuration>

Let’s comment on the connection string part, driver, and dialect part from the code-based configuration, because the program will read it from the hibernate.cfg.xml file and the LogSqlInConsole part will remain in the code-based configuration.

using HibernatingRhinos.Profiler.Appender.NHibernate; 
using NHibernate.Cfg; 
using NHibernate.Dialect; 
using NHibernate.Driver; 

using System; 
using System.Linq; 
using System.Reflection;
namespace NHibernateDemoApp { 
   
   class Program { 
	
      static void Main(string[] args) { 
		
         NHibernateProfiler.Initialize(); 
         var cfg = new Configuration();
			
         String Data Source = asia13797\\sqlexpress;
         String Initial Catalog = NHibernateDemoDB;
         String Integrated Security = True;
         String Connect Timeout = 15;
         String Encrypt = False;
         String TrustServerCertificate = False;
         String ApplicationIntent = ReadWrite;
         String MultiSubnetFailover = False;
			
         cfg.DataBaseIntegration(x = > { //x.ConnectionString = "Data Source + 
            Initial Catalog + Integrated Security + Connect Timeout + Encrypt +
            TrustServerCertificate + ApplicationIntent + MultiSubnetFailover";
				
            //x.Driver<SqlClientDriver>(); 
            //x.Dialect<MsSql2008Dialect>(); 
            x.LogSqlInConsole = true; 
         }); 
         
         cfg.Configure(); 
         cfg.AddAssembly(Assembly.GetExecutingAssembly()); 
         var sefact = cfg.BuildSessionFactory(); 
			
         using (var session = sefact.OpenSession()) { 
			
            using (var tx = session.BeginTransaction()) { 
               
               var students = session.CreateCriteria<Student>().List<Student>();
               Console.WriteLine("\nFetch the complete list again\n"); 
               
               foreach (var student in students) { 
                  Console.WriteLine("{0} \t{1} \t{2} \t{3}", student.ID,
                  student.FirstName, student.LastName, student.AcademicStanding); 
               } 
					
               tx.Commit(); 
            }
				
            Console.ReadLine(); 
         } 
      } 
   } 
}

Now when you run the application, you will see that the program has read the log from code-based configuration and other configuration from the hibernate.cfg.xml file.

NHibernate: SELECT this_.ID as ID0_0_, this_.LastName as LastName0_0_,   
   this_.FirstMidName as FirstMid3_0_0_, this_.AcademicStanding as Academic4_0_0_ FROM
   Student this_

Fetch the complete list again
1 Allan Bommer Excellent
2 Jerry Lewis Good

So now we have got some of our configuration inside of our hibernate.cfg.xml file, some of it is inside of the code-based configuration and depending on the order of calling code-based versus configure(), we can change which of them overrides the other.

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