Validating User Input - Stripes...and Java Web Development is Fun Again - page 83

Source Page Resolution
To determine the page from which a request came from,
Stripes calls the getSourcePageResolution ( ) method of the Action-
BeanContext class. This method uses the _sourcePage request
parameter, which is automatically generated by Stripes.
• If we delete all errors from the list and return null , it's as if those
errors never happened. Only in this case is the event handler exe-
cuted.
For example:
public class MyActionBean extends BaseActionBean
implements ValidationErrorHandler
{
Resolution handleValidationErrors(ValidationErrors errors) {
if (specialSituation) {
return new ForwardResolution("/WEB-INF/jsp/special.jsp");
}
if (bypassErrors) {
errors.clear();
}
return null ;
}
}
If the specialSituation flag is true , the user is sent directly to special.jsp .
If the bypassErrors flag is true , the event handler is executed because the
list of errors is emptied before returning null . If neither flag is true , the
user is sent back to the source page because the method returns null
but the list still contains errors.
The custom methods part of the validation process is summarized in
Figure 4.9 , on the following page. With validation methods and the han-
dleValidationErrors ( ) method of the ValidationErrorHandler interface, we have
full control over what happens after the built-in validations have been
executed. We can run custom validation methods and control what hap-
pens when errors have occurred.
Validation in the Event Handler
Finally, we may encounter situations where the validation that we want
to perform just doesn't fit anywhere in the validation process.