Validating User Input - Stripes...and Java Web Development is Fun Again - page 78

there are previous validation errors. The value must be a ValidationState ,
which is an enum with these possible values:
• ALWAYS : Executes the validation method even if there are previous
validation errors
• NO_ERRORS : Executes the validation method only if there are no
previous validation errors
• DEFAULT : Uses the default behavior of the application
For example, this validation method will be executed regardless of pre-
vious errors:
@ValidationMethod(when=ValidationState.ALWAYS)
public void validateSomething(ValidationErrors errors) {
// ...
}
The default value of when= is, not surprisingly, ValidationState.DEFAULT .
This means “use the application's default,” and that default is Validation-
State.NO_ERRORS . You can change the “application default” to Validation-
State.ALWAYS by adding an initialization parameter to the Stripes filter
in web.xml :
<filter>
<filter-name> StripesFilter </filter-name>
<filter-class>
net.sourceforge.stripes.controller.StripesFilter
</filter-class>
<!-- ... -->
<init-param>
<param-name> Validation.InvokeValidateWhenErrorsExist </param-name>
<param-value> true </param-value>
</init-param>
</filter>
With this configuration, validation methods will always be executed by
default. To execute a validation method only if there are no previous
errors, you'd have to explicitly add when=ValidationState.NO_ERRORS to
@ValidationMethod .
Whether you are changing the default or using the when= attribute,
when you execute a validation method even if previous errors have
occurred, the fields could contain invalid values or even be null . Keep
that in mind when writing the code for a validation method that will
always be executed.