Try using the validatePage method which will validate the data being submitted. The page param can be used to define specifically how to validate and save the data.
Define the _target<pageNumber> in your form submission. This will define what page will be displayed after the form has been submitted. You will more than likely want to ensure the allowDirtyForward and allowDirtyBack values are set to true.
protected void validatePage(Object command,Errors errors,int page)
Let me know if this works. I'll watch the thread.
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