This is blocker issue for RHV 4.0, exact issue is tracked under https://bugzilla.redhat.com/1400619

In short we are using symlinks in war deployments and allowing symlinks feature using <symbolic-linking-enabled>true</symbolic-linking-enabled> in jboss-web.xml. This was working fine in JBoss EAP 7.0.3.GA (WildFly Core 2.1.9.Final-redhat-1) and WildFly 10.1, but it suddenly stopped working in JBoss EAP 7.0.4.GA (WildFly Core 2.1.10.Final-redhat-1) and following error is raised when trying to access web application URL:

2016-12-02 03:42:12,876 ERROR [io.undertow.request] (default task-8) UT005023: Exception handling request to /ovirt-engine/: org.apache.jasper.JasperException: JBWEB004001: Unable to compile class for JSP
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:667) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:358) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:402) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:346) [jastow.jar:2.0.0.Final-redhat-1]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) [jboss-servlet-api_3.1_spec.jar:1.0.0.Final-redhat-1]
at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.FilterHandler.handleRequest(FilterHandler.java:81) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.jsp.JspFileHandler.handleRequest(JspFileHandler.java:32) [jastow.jar:2.0.0.Final-redhat-1]
at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) [undertow-core.jar:1.3.25.Final-redhat-1]
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) [undertow-core.jar:1.3.25.Final-redhat-1]
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) [undertow-core.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:266) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.ServletInitialHandler.dispatchToServlet(ServletInitialHandler.java:211) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.spec.RequestDispatcherImpl.includeImpl(RequestDispatcherImpl.java:352) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.spec.RequestDispatcherImpl.include(RequestDispatcherImpl.java:265) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at org.ovirt.engine.core.WelcomeServlet.doGet(WelcomeServlet.java:154) [welcome.jar:]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:687) [jboss-servlet-api_3.1_spec.jar:1.0.0.Final-redhat-1]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) [jboss-servlet-api_3.1_spec.jar:1.0.0.Final-redhat-1]
at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:129) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at org.ovirt.engine.core.branding.BrandingFilter.doFilter(BrandingFilter.java:73) [branding.jar:]
at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at org.ovirt.engine.core.utils.servlet.LocaleFilter.doFilter(LocaleFilter.java:66) [utils.jar:]
at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at org.ovirt.engine.core.utils.servlet.HeaderFilter.doFilter(HeaderFilter.java:94) [utils.jar:]
at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.FilterHandler.handleRequest(FilterHandler.java:84) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) [undertow-core.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) [undertow-core.jar:1.3.25.Final-redhat-1]
at io.undertow.security.handlers.AuthenticationConstraintHandler.handleRequest(AuthenticationConstraintHandler.java:51) [undertow-core.jar:1.3.25.Final-redhat-1]
at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46) [undertow-core.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.security.ServletSecurityConstraintHandler.handleRequest(ServletSecurityConstraintHandler.java:59) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60) [undertow-core.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50) [undertow-core.jar:1.3.25.Final-redhat-1]
at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43) [undertow-core.jar:1.3.25.Final-redhat-1]
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) [undertow-core.jar:1.3.25.Final-redhat-1]
at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) [undertow-core.jar:1.3.25.Final-redhat-1]
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43) [undertow-core.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:285) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:264) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:175) [undertow-servlet.jar:1.3.25.Final-redhat-1]
at io.undertow.server.Connectors.executeRootHandler(Connectors.java:207) [undertow-core.jar:1.3.25.Final-redhat-1]
at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:802) [undertow-core.jar:1.3.25.Final-redhat-1]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [rt.jar:1.8.0_111]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [rt.jar:1.8.0_111]
at java.lang.Thread.run(Thread.java:745) [rt.jar:1.8.0_111]
Caused by: java.lang.NullPointerException
at org.apache.jasper.compiler.TagLibraryInfoImpl.createTagFileInfo(TagLibraryInfoImpl.java:468) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.compiler.TagLibraryInfoImpl.<init>(TagLibraryInfoImpl.java:180) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.compiler.Parser.parseTaglibDirective(Parser.java:412) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.compiler.Parser.parseDirective(Parser.java:475) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.compiler.Parser.parseElements(Parser.java:1456) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.compiler.Parser.parse(Parser.java:143) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.compiler.ParserController.doParse(ParserController.java:223) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.compiler.ParserController.parse(ParserController.java:102) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:200) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:354) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:334) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:321) [jastow.jar:2.0.0.Final-redhat-1]
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:652) [jastow.jar:2.0.0.Final-redhat-1]
... 59 more

If we replace symlinks in war deployment with real files, everything works fine.