Performing Presentation Validation
This chapter has touched on performing your
application’s input
validation
in the validate( )
method of the
ActionForm
. You can create whatever presentation
validation rules you need in this method. For example, the
LoginForm
from Example 7-2
validated that the email and password fields were entered and were
not empty strings. Although this is a trivial example, you can
validate anything you like. A common validation rule is to ensure
that a string value that should be a number is in fact a string
representation of a valid number. The validate( )
routine for this rule might look like the one in Example 7-5.
Example 7-5. Performing a number validation rule
public ActionErrors validate(ActionMapping mapping, HttpServletRequest request) { ActionErrors errors = new ActionErrors( ); String orderQtyStr = getQuantity( ); if( orderQtyStr == null || orderQtyStr.length( ) < 1 ){ errors.add( ActionErrors.GLOBAL_ERROR, new ActionError( "order.quantity.required" )); } // Validate that the qty entered was in fact a number try{ // Integer.parse was not used because it's not really I18N-safe java.text.Format format = java.text.NumberFormat.getNumberInstance( ); Number orderQty = (Number)format.parseObject( orderQtyStr ); }catch( Exception ex ){ // The quantity entered by the user was not a valid qty errors.add( ActionErrors.GLOBAL_ERROR, new ActionError( "order.quantity.invalid" )); } return errors; }
As you can imagine, web applications often need to check for ...
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