It is an error to omit the input
attribute for named Struts actions that can return valdiation errors..
The struts specification requires an input
attribute whenever a named action returns validation errors[2]. The input
attribute specifies the page used to display error messages when validation errors occur.
Example 1: The following configuration defines a named validating action, but does not specify an input
attribute.
<action-mappings>
<action path="/Login"
type="com.LoginAction"
name="LoginForm"
scope="request"
validate="true" />
</action-mappings>
[1] Apache Struts 1.3 Specification
[2] struts-config_1_3.dtd