e Struts//XWork Validator 1.0.3//EN" "http://struts.apache.org/dtds/xwork-validator-1.0.3.dtd"> <validators> <field name="bar"> <field-validator type="required"> <message>You must enter a value for bar.</message> </field-validator> <field-validator type="int"> <param name="min">6</param> <param name="max">10</param> <message>bar must be between ${min} and ${max}, current value is ${bar}.</message> </field-validator> </field> <field name="bar2"> <field-validator type="regex"> <param name="expression">[0-9],[0-9]</param> <message>The value of bar2 must be in the format "x, y", where x and y are between 0 and 9</message> </field-validator> </field> <field name="date"> <field-validator type="date"> <param name="min">12/22/2002</param> <param name="max">12/25/2002</param> <message>The date must be between 12-22-2002 and 12-25-2002.</message> </field-validator> </field> <field name="foo"> <field-validator type="int"> <param name="min">0</param> <param name="max">100</param> <message key="foo.range">Could not find foo.range!</message> </field-validator> </field> <validator type="expression"> <param name="expression">foo lt bar </param> <message>Foo must be greater than Bar. Foo = ${foo}, Bar = ${bar}.</message> </validator> </validators>
Here we can see the configuration of validators for the SimpleAction class. Validators (and field-validators) must have a type attribute, which refers to a name of an Validator registered with the ValidatorFactory as above. Validator elements may also have <param> elements with name and value attributes to set arbitrary parameters into the Validator instance. See below for discussion of the message element.
Each Validator or Field-Validator element must define one message element inside the validator element body. The message element has 1 attributes, key which is not required. The body of the message tag is taken as the default message which should be added to the Action if the validator fails. Key gives a message key to look up in the Action's ResourceBundles using getText() from LocaleAware if the Action implements that interface (as ActionSupport does). This provides for Localized messages based on the Locale of the user making the request (or whatever Locale you've set into the LocaleAware Action). After either retrieving the message from the ResourceBundle using the Key value, or using the Default message, the current Validator is pushed onto the ValueStack, then the message is parsed for \$\{...\} sections which are replaced with the evaluated value of the string between the \$\{ and \}. This allows you to parameterize your messages with values from the Validator, the Action, or both.
If the validator fails, the validator is pushed onto the ValueStack and the message - either the default or the locale-specific one if the key attribute is defined (and such a message exists) - is parsed for ${...} sections which are replaced with the evaluated value of the string between the ${ and }. This allows you to parameterize your messages with values from the validator, the Action, or both.
NOTE: Since validation rules are in an XML file, you must make sure you escape special characters. For example, notice that in the expression validator rule above we use ">" instead of ">". Consult a resource on XML for the full list of characters that must be escaped. The most commonly used characters that must be escaped are: & (use &), > (user >), and < (use <).
Here is an example of a parameterized message:
This will pull the min and max parameters from the IntRangeFieldValidator and the value of bar from the Action.
bar must be between ${min} and ${max}, current value is ${bar}. Another notable fact is that the provided message value is capable of containing OGNL expressions. Keeping this in mind, it is possible to construct quite sophisticated messages.
See the following example to get an impression:
${getText("validation.failednotice")}! ${getText("reason")}: ${getText("validation.inputrequired")}
@version $Date$ $Id$
@author Jason Carreira
@author James House