超级简单的struts问题，可是我不明白(愧)......

你这里有错误：
class的名字是LogonActive
而这里是
<action-mappings>
        <action path="/logon"
                type="myTest.LogonAction"
                ~~~~~~~~~~~~~~~~~~~~~~~~~~~
                name="logonForm"
                scope="request"
                input="/index.jsp">
            <forword name="success" path="/welcome.jsp"/>
        </action>
    </action-mappings>
所以你的LogonActive和LogonAction名字不一致引起了错误