Apache Struts 2 Documentation > Home > Guides > Core Developers Guide > Validation > requiredstring validator


RequiredStringValidator checks that a String field is non-null and has a length > 0. (i.e. it isn't ""). The "trim" parameter determines whether it will {@link String#trim() trim} the String before performing the length check. If unspecified, the String will be trimmed.


  • fieldName - The field name this validator is validating. Required if using Plain-Validator Syntax otherwise not required
  • trim - trim the field name value before validating (default is true)


    <!-- Plain-Validator Syntax -->
    <validator type="requiredstring">
        <param name="fieldName">username</param>
        <param name="trim">true</param>
        <message>username is required</message>
    <!-- Field-Validator Syntax -->
    <field name="username">
    	  <field-validator type="requiredstring">
            <param name="trim">true</param>
            <message>username is required</message>