[[validate]]
= `validate...()`

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The `validate...()` supporting method is called for properties, actions and action parameters. 

When a validating method is returning any non-empty _String_, the validation is considered a failure, that is brought to the user's attention. 

[source,java]
.using _validate_ for an action parameter
----
import lombok.Getter;
import lombok.Setter;

public class Customer {

    @Property
    @Getter @Setter
    private Product product;

    public String validateProduct( // <.>
            final Product product) { 
        // ...
    }

    // ...
}
----
<.> validating a property's setter argument

[source,java]
.using _validate_ for an action
----
public class Customer {

    public Order placeOrder(
            final Product product,
            final int quantity) {
        // ...
    }
    
    public String validatePlaceOrder( // <.>
            final Product product,
            final int quantity) {
        // ...
    }

    // ...
}
----
<.> validating the action considering all its parameters

[source,java]
.using _validate_ for an action parameter
----
public class Customer {

    public Order placeOrder(
            final Product product,
            final int quantity) {
        // ...
    }
    
    public String validate0PlaceOrder( // <.>
            final Product product) { 
        // ...
    }

    // ...
}
----
<.> validating the action's first parameter
