Servlet Web.xml配置问题！请高手指教！
------------------------------错误信息----------------------------------
type   Exception   report

message  

description   The   server   encountered   an   internal   error   ()   that   prevented   it   from   fulfilling   this   request.

exception  

javax.servlet.ServletException:   Error   allocating   a   servlet   instance
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870)
org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
java.lang.Thread.run(Unknown   Source)


root   cause  

java.lang.NoClassDefFoundError:   IllegalName:   ok/Login
java.lang.ClassLoader.preDefineClass(Unknown   Source)
java.lang.ClassLoader.defineClass(Unknown   Source)
java.security.SecureClassLoader.defineClass(Unknown   Source)
org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1847)
org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:873)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1326)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1205)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870)
org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
java.lang.Thread.run(Unknown   Source)


note   The   full   stack   trace   of   the   root   cause   is   available   in   the   Apache   Tomcat/5.5.23   logs.

项目结构：xxx/index.jsp,
                    xxx/web-inf/xml
                    xxx/web-inf/classes/ok/Login.class
------------------------------web.xml----------------------------------
<?xml   version= "1.0 "   encoding= "ISO-8859-1 "?>
<web-app   xmlns= "http://java.sun.com/xml/ns/j2ee "
        xmlns:xsi= "http://www.w3.org/2001/XMLSchema-instance "
        xsi:schemaLocation= "http://java.sun.com/xml/ns/j2ee   http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd "
        version= "2.4 ">

    <display-name> Welcome   to   Tomcat </display-name>
    <description>
          ServLet   Web.xml   Test
    </description>

<!--   JSPC   servlet   mappings   start   -->