Ti sei dimenticato la proprieta action nel tag form. Infatti è required. Quarta il tld
<tag>
<name>form</name>
<tagclass>org.apache.struts.taglib.html.FormTag</tagclass>
<bodycontent>JSP</bodycontent>
-
<attribute>
<name>action</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>acceptCharset</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>disabled</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>enctype</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>focus</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>focusIndex</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>method</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>onreset</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>onsubmit</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>readonly</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>scriptLanguage</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>style</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>styleClass</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>styleId</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
-
<attribute>
<name>target</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>