Advancing to the next panel during the installation can be controlled using validators.

This can be achieved by a nested <validator> definition in the panel definition in the installer descriptor:

<panels>
    ...
    <panel classname="TargetPanel">
      <validator classname="com.izforge.izpack.installer.validator.ConditionValidator"/>
    </panel>
    ...
</panels>

Either Built-in validators or user-defined validators can be used. User-defined validators must in a library specified in a <jar> tag.

There can be any number of validators nested in a <panel> definition. All of the validators must evaluate to true for the final status to be true, 

If any of the unconditioned validators or those that are active by a condition fails the user is prevented from advancing to the next panel using the Next button. Instead, an error or warning message is shown.

The validator determines whether a warning or an error messagebox is shown. It also controls the message translation.

A <validator> tag takes the following attributes:

AttributeDescriptionValuesRequired
className

Fully qualified classname of an validator implementation.

This can be a built-in validator or user-defined .

Stringyes
conditionCondition for applying this validator. If this condition evaluates false, the validator is ignoredStringno