Exclusive Optionals

When you are developing a module that provides several ways of configuring the same thing, but only one of them should be used, you might need to set the following rule:

From a given set of parameters, only one shall be used at any time.

You use @ExclusiveOptionals to enforce this restriction.

@ExclusiveOptionals

The @ExclusiveOptionals annotation can only be used on types that are used as a @ParameterGroup (see Parameters for details).

Example

@ExclusiveOptionals
public class ExclusiveOptionalsExample {

    @Parameter
    private String requiredParameter;

    @Parameter
    @Optional
    private String optionalParameter;

    @Parameter
    @Optional
    private String anotherOptionalParameter;
}

As the name of the annotation implies, the exclusivity restriction only applies to the optional parameters. So, setting requiredParameter at the same time as optionalParameter or anotherOptionalParameter is allowed, but setting optionalParameter and anotherOptionalParameter at the same time causes an error to be thrown.

Tip: You can have as many parameters as you want inside an object that is annotated with @ExclusiveOptionals, but only one optional parameter is allowed to be set at any time.

Enforcing At Least One Parameter

There can be cases where exactly one (but no more than one) of the optional parameters must be set. You can configure this requirement by using @ExclusiveOptionals(isOneRequired = true), for example:

@ExclusiveOptionals(isOneRequired = true)
public class OneRequiredExample {

    @Parameter
    private String requiredParameter;

    @Parameter
    @Optional
    private String optionalParameter;

    @Parameter
    @Optional
    private String anotherOptionalParameter;
}

So, an error is thrown if you set requiredParameter but do not set one of the optional parameters: optionalParameter or anotherOptionalParameter.