帮忙看看这是因为什么报错 javax.servlet.ServletExcept?报错

C:\Java\jdk1.6.0_18\lib\tools.jar;D:\tomcat6.0\bin\bootstrap.jar
javax.servlet.ServletException: java.lang.NoClassDefFoundError: javaxrvlet/js
p/jstl/core/LoopTag
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:275)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:206)
        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDisp
atcher.java:630)
        at org.apache.catalina.core.ApplicationDispatcher.processRequest(Applica
tionDispatcher.java:436)
        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationD
ispatcher.java:374)
        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDis
patcher.java:302)
        at com.sundoctor.example.servlet.JobProcessServlet.getQrtzTriggers(JobPr
ocessServlet.java:186)
        at com.sundoctor.example.servlet.JobProcessServlet.service(JobProcessSer
vlet.java:64)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV
alve.java:233)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV
alve.java:191)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j
ava:128)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j
ava:102)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal
ve.java:109)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.jav
a:286)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java
:845)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.proce
ss(Http11Protocol.java:583)
        at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:44
7)
        at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NoClassDefFoundError: javaxrvlet/jsp/jstl/core/LoopTag
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:14
1)
        at org.apache.catalina.loader.WebappClassLoader.findClassInternal(Webapp
ClassLoader.java:1847)
        at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoa
der.java:890)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoa
der.java:1354)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoa
der.java:1233)
        at org.apache.jasper.compiler.Parser.parseCustomTag(Parser.java:1239)
        at org.apache.jasper.compiler.Parser.parseElements(Parser.java:1467)
        at org.apache.jasper.compiler.Parser.parse(Parser.java:138)
        at org.apache.jasper.compiler.ParserController.doParse(ParserController.
java:216)
        at org.apache.jasper.compiler.ParserController.parse(ParserController.ja
va:103)
        at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:154)
        at org.apache.jasper.compiler.Compiler.compile(Compiler.java:315)
        at org.apache.jasper.compiler.Compiler.compile(Compiler.java:295)
        at org.apache.jasper.compiler.Compiler.compile(Compiler.java:282)
        at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext
.java:586)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper
.java:317)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:3
42)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
        ... 22 more
Caused by: java.lang.ClassNotFoundException: javax.servlet.jsp.jstl.core.LoopTag

        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoa
der.java:1387)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoa
der.java:1233)
        ... 43 more