Servlet.service() for servlet jsp threw exception java.lang.NullPointerException
第一次运行的时候是正常的，如果不更改页面内容，操作也没有问题。但是只要修改了页面上面的内容，执行之后就会出现这种错误，在网上看了下别人说的解决方法，有可能是我引用的tomcat-api.jar与tomcat自带的包冲突了，删除了之后还是会出现上面的情况下面是错误内容：
Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
at org.apache.taglibs.standard.tlv.JstlBaseTLV.validate(JstlBaseTLV.java:149)
at org.apache.taglibs.standard.tlv.JstlCoreTLV.validate(JstlCoreTLV.java:105)
at org.apache.jasper.compiler.TagLibraryInfoImpl.validate(TagLibraryInfoImpl.java:949)
at org.apache.jasper.compiler.Validator.validateXmlView(Validator.java:1921)
at org.apache.jasper.compiler.Validator.validate(Validator.java:1888)
at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:223)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:625)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:492)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:378)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:749)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:487)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:412)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:339)
at com.jfinal.render.JspRender.render(JspRender.java:56)
at com.jfinal.core.ActionHandler.handle(ActionHandler.java:92)
at com.jfinal.core.JFinalFilter.doFilter(JFinalFilter.java:72)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744) --------------------编程问答-------------------- 你 传入 jstl 标签的内容是个 null --------------------编程问答-------------------- jar 包有问题、 --------------------编程问答-------------------- 你项目中是不是有了servelt-api.jar,standard.jar,jstl.jar? --------------------编程问答-------------------- standard.jar,jstl.jar这2个包有，不然会报错。jstl的标签内容不是空的，第一次显示是正常的，只要不修改页面上的东西，就没有任何问题。
补充：Java , Java EE
