=== Mandatory vs Optional

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By default, the framework assumes that all parameters of an action are required (mandatory).
The xref:refguide:applib:index/annotation/Parameter.adoc#optionality[optionality()] element allows this to be relaxed.

[TIP]
====
The attribute has no meaning for a primitive type such as `int`: primitives will always have a default value (e.g. zero).
If optionality is required, then use the corresponding wrapper class (e.g. `java.lang.Integer`) and annotate with `Parameter#optionality()` as required.
====

The values for the attribute are simply `OPTIONAL` or `MANDATORY`.

For example:

[source,java]
----
public class Customer {
    public Order placeOrder(
            final Product product,
            final int quantity,
            @Parameter(optionality = Optionality.OPTIONAL)
            final String specialInstructions) {
        ...
    }
    ...
}
----

==== Alternatives

It is also possible to specify optionality using xref:refguide:applib-ant:Nullable.adoc[@Nullable] annotation.
