== Example

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:page-partial:

For example:

[source,java]
----
@DomainObject(
    auditing=Auditing.ENABLED,
    autoCompleteRepository=CustomerRepository.class
    editing=Editing.ENABLED,
    updatedLifecycleEvent=Customer.UpdatedEvent.class

)
public class Customer {
    ...
}
----



[#view-models]
== View Models

The `@DomainObject(nature=VIEW_MODEL)` annotation, applied to a class, indicates that the class is a view model.

View models are not persisted to the database, instead their state is encoded within their identity (ultimately represented in the URL).


For example:

[source,java]
----
@DomainObject(nature=VIEW_MODEL)
public class CustomerViewModel {
    public CustomerViewModel() {}
    public CustomerViewModel(String firstName, int lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }
    ...
}
----

Although there are several ways to instantiate a xref:userguide:ROOT:view-models.adoc[view model], we recommend that they are instantiated using an N-arg constructor that initializes all relevant state.
The xref:refguide:applib:index/services/registry/ServiceRegistry.adoc[ServiceRegistry] can then be used to inject dependencies into the view model.
For example:

[source,java]
----
Customer cust = ...
CustomerViewModel vm = factoryService.viewModel(
    new CustomerViewModel(cust.getFirstName(), cust.getLastName()));
----

The view model's memento will be derived from the value of the view model object's properties.
Any properties annotated with xref:refguide:applib:index/annotation/Programmatic.adoc[@Programmatic] will be excluded from the memento.
Properties that are merely xref:refguide:applib:index/annotation/Property.adoc#hidden[hidden] _are_ included in the memento.

View models when defined using `@DomainObject(nature=VIEW_MODEL)` have some limitations:

* view models cannot hold collections other view models (simple properties _are_ supported, though)
* collections (of either view models or entities) are ignored.
* not every data type is supported,

However, these limitations do _not_ apply to xref:userguide:ROOT:view-models.adoc#jaxb[JAXB] view models.
If you are using view models heavily, you may wish to restrict yourself to just the JAXB flavour.


