You need to use a custom-createMethod. http://dozer.sourceforge.net/documentation/customCreateMethod.html
Something like this:
<mapping>
<class-a>hl.test.dozer03.form.Form</class-a>
<class-b create- method="PersonContainerFactory.createPersonContainer">hl.test.dozer03.result.PersonContainer</class-b>
<field>
<a>firstNameEmployee</a>
<b>person.firstName</b>
</field>
<field>
<a>lastNameEmployee</a>
<b>person.lastName</b>
</field>
</mapping>
With the java class:
public class PersonContainerFactory {
public static PersonContainer createPersonContainer(){
PersonContainer cont = new PersonContainer();
cont.setPerson(new Employee());
return classA;
}
}