unique in .hbm.xml file not raising exception

问题

I am having the following in my .hbm.xml file

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                                    namespace="Core.Domain.Model"
                                    assembly="Core">

  <class name="Category" table="Categories" dynamic-update="true">
    <cache usage="read-write"/>
    <id name="Id" column="Id" type="Guid">
      <generator class="guid"/>
    </id>
    <property name="Name" length="100">
    <column name="Name" unique="true" index="IX_Category"/>
    </property>
  </class>
</hibernate-mapping>

I am having the following code, however, I can see that no exception is being raised when I am inserting a duplicate value for the Name field. Why is that so?

 void IRepository<Category>.Save(Category entity)
        {
            using (var scope = new TransactionScope(TransactionScopeOption.Required))
            {
            using (ISession session = NHibernateHelper.OpenSession())
            {
                using (ITransaction transaction = session.BeginTransaction())
                {
                    session.Save(entity);
                    transaction.Commit();
                }
            }
            scope.Complete();
            }    
        }

回答1:

The unique attribute is only used when generating a DDL schema from a mapping (hbm).

If you want to check uniqueness with NHibernate, it is data validation and you should look NHibernate validator. And as Rafael said you have to write your own validator.

You can also check the natural-id element.

Unless you absolutely need to validate uniqueness on application side, this sample and this one make me think it may be better to let the database do this job.

回答2:

Did NHibernate generate the database schema for you? Because even though you set the property as unique, if the schema does not have the unique constraint, it will do nothing. Basically, that property won't query the database looking for uniqueness; it will only set the SQL constraint on insert.

来源：https://stackoverflow.com/questions/3726478/unique-in-hbm-xml-file-not-raising-exception

标签

nhibernate

nhibernate-mapping