The <properties> element allows the definition of a named, logical grouping of properties of a class. The most important use of the construct is that it allows a combination of properties to be the target of a property-ref. It is also a convenient way to define a multi-column unique constraint.

<properties 
        name="logicalName" 
        insert="true|false"
        update="true|false"
        optimistic-lock="true|false"
        unique="true|false"
>
        
        <property ...../>
        <many-to-one .... />
        ........
</properties>

name: The logical name of the grouping - not an actual property name.

insert: Do the mapped columns appear in SQL INSERT s?

update: Do the mapped columns appear in SQL UPDATE s?

optimistic-lock (optional - defaults to true): Specifies that updates to these properties do or do not require acquisition of the optimistic lock. In other words, determines if a version increment should occur when these properties are dirty.

unique (optional - defaults to false): Specifies that a unique constraint exists upon all mapped columns of the component.

For example, if we have the following <properties> mapping:

<class name="Person">
    <id name="personNumber"/>
    ...
    <properties name="name" 
            unique="true" update="false">
        <property name="firstName"/>
        <property name="initial"/>
        <property name="lastName"/>
    </properties>
</class>

Then we might have some legacy data association which refers to this unique key of the Person table, instead of to the primary key:

<many-to-one name="person" 
         class="Person" property-ref="name">
    <column name="firstName"/>
    <column name="initial"/>
    <column name="lastName"/>
</many-to-one>

We don't recommend the use of this kind of thing outside the context of mapping legacy data.