  <p>Declares that this attribute must be a <code>ValueExpression</code>
                whose expected type is given by the value of this attribute. If
                not
                specified, and no "method-signature" attribute is present,
                <code>java.lang.Object</code> is assumed. This
                attribute is mutually
                exclusive with the "method-signature" attribute. If both attributes are
                present, the
                "method-signature" attribute i