Apache Struts 2 Documentation > Home > Guides > Core Developers Guide > Validation > required validator |
RequiredFieldValidator checks if the specified field is not null.
<validators> <!-- Plain Validator Syntax --> <validator type="required"> <param name="fieldName">username</param> <message>username must not be null</message> </validator> <!-- Field Validator Syntax --> <field name="username"> <field-validator type="required"> <message>username must not be null</message> </field-validator> </field> </validators>