Class file uses import but reports Unresolved compilation problems

Question

I am having an issue resulting in the "Unresolved compilation problems" error. I have looked at this SO question, as well as this one of the same nature and finally this one again describing the same error.

All three of those describe dealing with compilation errors, but when I compile my project's class files, either using Maven from inside eclipse, Maven from the command line, or just the javac command, no errors are reported.

We have a custom class, JmxTools, which uses import org.apache.commons.modeler.Registry; Now the source file does not complain about a missing import.

An answer to a similar question suggests looking at the "Problems" view in eclipse. This shows no errors

So, everything compiles fine, the commons-modeler jar is in my Maven dependencies. Yet when I run my web app and call the page using the JmxTools class I receive the following error stack:

    org.apache.jasper.JasperException: javax.servlet.ServletException: java.lang.Error: Unresolved compilation problems: 

    The import org.apache.commons.modeler cannot be resolved
    Registry cannot be resolved to a type
    Registry cannot be resolved to a type
    Registry cannot be resolved
    Registry cannot be resolved
    Registry cannot be resolved to a type
    Registry cannot be resolved to a type
    at 

    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:561)
        at 

org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:462)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at com.gy.filters.AccessControlFilter.doFilter(AccessControlFilter.java:150)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1115)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2549)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2538)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)

    Caused by: javax.servlet.ServletException: java.lang.Error: Unresolved compilation problems: 
    The import org.apache.commons.modeler cannot be resolved
    Registry cannot be resolved to a type
    Registry cannot be resolved to a type
    Registry cannot be resolved
    Registry cannot be resolved
    Registry cannot be resolved to a type
    Registry cannot be resolved to a type

    at org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:916)
    at org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:845)
    at org.apache.jsp.contextlist_jsp._jspService(contextlist_jsp.java:148)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:439)
    ... 26 more

    Caused by: java.lang.Error: Unresolved compilation problems: 
        The import org.apache.commons.modeler cannot be resolved
        Registry cannot be resolved to a type
        Registry cannot be resolved to a type
        Registry cannot be resolved
        Registry cannot be resolved
        Registry cannot be resolved to a type
        Registry cannot be resolved to a type

        at com.gy.admin.JmxTools.<init>(JmxTools.java:18)
        at org.apache.jsp.contextlist_jsp._jspService(contextlist_jsp.java:100)
        ... 29 more

How do I get around this? This is something I have not run into before and the answers to similar questions do not appear to apply to this situation

EDIT

Following Kayaman's advice:

Checked the war file and the commons-modeler jar file is present in WEB-INF/lib
Moved the commons-modeler jar from from the war to my tomcat's lib/ folder
did a fresh clean, then compile, the package from the command line

Unfortunately, none of these helped the situation. I am still receiving the error.

@bcsb1001 the bulk of those warnings are barking about generic types needing to be paramertized — Paul Stoner, Apr 04 '18 at 17:12
@Kayaman the warnings or the fact the jar is scoped for compile? I assume I should change it to provided? — Paul Stoner, Apr 04 '18 at 17:14
No, the scope should be fine, but it's not being found by the JSP compiler. Can you check the war file and see if the library is included correctly? You can also try putting the library in your app server's `lib` directory just to check if it fixes the problem (although it doesn't fix the root of the problem, but you gotta start somewhere). — Kayaman, Apr 04 '18 at 17:16
Also try cleaning and rebuilding the project. From commandline, not from Eclipse. It could be Eclipse causing trouble too. — Kayaman, Apr 04 '18 at 17:25

score 1 · Accepted Answer · answered Apr 05 '18 at 12:58

I wish to thank Kayaman. My issue was resolved by doing numerous maven clean then compile then package steps, outside of eclipse.

I also had to do several cleans and republish of tomcat inside of eclipse.

I also removed the errant dependency altogether built and packaged the project, then added the dependency back in.

I'm not exactly sure which of these steps solved my issue. I was in the middle of trying/testing various solutions when it started working.

Class file uses import but reports Unresolved compilation problems

1 Answers1