Skip to main content

Saving NHibernate objects with assigned id’s

One of the great features of Nhibernate is that it manages persistance for us. You just attach an object to the session and NHibernate will figure out if this object is added or changed. But how does NHibernate knows the difference between a new and existing object?

By default it uses the value we assigned to the unsaved-value attribute on the id mapping. This means that if the id of our object is equal to our unsaved-value that NHibernate will detect this object as new and do an INSERT statement. If the id value is different from our unsaved-value NHibernate will generate an UPDATE statement instead.

 

   1:  <hibernate-mapping default-cascade="none" xmlns="urn:nhibernate-mapping-2.2">
   2:    <class name="Test.Data.Domain.Category, Test.Data" table="Categories" lazy="true">
   3:      <id name="CategoryID" type="System.Int32" column="CategoryID" unsaved-value="0">
   4:        <generator class="native" />
   5:      </id>
   6:    </class>
   7:  </hibernate-mapping>


Sounds easy but what if you are using a composite key? In that case using the unsaved-value makes no sense. If we have a look at the documentation NHibernate gives us a second option:

A version or timestamp property should never be null for a detached instance, so Hibernate will detact any instance with a null version or timestamp as transient, no matter what other unsaved-value strategies are specified. Declaring a nullable version or timestamp property is an easy way to avoid any problems with transitive reattachment in Hibernate, especially useful for people using assigned identifiers or composite keys!

So if you leave your version column empty, NHibernate will always detect the object as new.

Popular posts from this blog

DevToys–A swiss army knife for developers

As a developer there are a lot of small tasks you need to do as part of your coding, debugging and testing activities.  DevToys is an offline windows app that tries to help you with these tasks. Instead of using different websites you get a fully offline experience offering help for a large list of tasks. Many tools are available. Here is the current list: Converters JSON <> YAML Timestamp Number Base Cron Parser Encoders / Decoders HTML URL Base64 Text & Image GZip JWT Decoder Formatters JSON SQL XML Generators Hash (MD5, SHA1, SHA256, SHA512) UUID 1 and 4 Lorem Ipsum Checksum Text Escape / Unescape Inspector & Case Converter Regex Tester Text Comparer XML Validator Markdown Preview Graphic Color B

Help! I accidently enabled HSTS–on localhost

I ran into an issue after accidently enabling HSTS for a website on localhost. This was not an issue for the original website that was running in IIS and had a certificate configured. But when I tried to run an Angular app a little bit later on http://localhost:4200 the browser redirected me immediately to https://localhost . Whoops! That was not what I wanted in this case. To fix it, you need to go the network settings of your browser, there are available at: chrome://net-internals/#hsts edge://net-internals/#hsts brave://net-internals/#hsts Enter ‘localhost’ in the domain textbox under the Delete domain security policies section and hit Delete . That should do the trick…

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.