程序报错 Unable to compile class for JSP ,

报错如下: 

org.apache.jasper.JasperException: Unable to compile class for JSP:

An error occurred at line: 16 in the jsp file: /grstemp/SpecialModule/metropro/paiban/classBasic/classBasicSave.jsp
check cannot be resolved to a variable
13:       ClassBasic cb=new ClassBasic(pageContext);
14:       Integer check = cb.saveBasic(param);
15:      */
16:       out.println(JSONArray.fromObject(check));
17: %>


Stacktrace:
    at org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:92)
    at org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:330)
    at org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:439)
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:356)
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:334)
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:321)
    at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:592)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:328)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at com.grs.Filter.BaseFilter.doFilter(BaseFilter.java:58)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:861)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
    at java.lang.Thread.run(Thread.java:722)

这个问题一般与class文件出错有关,

如图,classpath文件在更新时出错, 导致项目无法编译生成相应的class文件

解决办法: 确保classpath正确后, 将Java Build Path 中有红叉的remove掉,重新 Add Library 一个

最后, clean项目,重新启动即可