H2 Console : NoClassDefFoundError on javax.servlet.http.HttpServlet

[Benoit Delagarde]

Hello,

I'm try to use the H2Console Servlet. I have add it in my web.xml, but i get the following error :

08:50:11,732 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-8) MSC000001: Failed to start service jboss.deployment.subunit."DivingReservationEAR.ear"."DivingReservationWeb.war".POST_MODULE: org.jboss.msc.service.StartException in service jboss.deployment.subunit."DivingReservationEAR.ear"."DivingReservationWeb.war".POST_MODULE: WFLYSRV0153: Failed to process phase POST_MODULE of subdeployment "DivingReservationWeb.war" of deployment "DivingReservationEAR.ear"
        at org.jboss...@18.0.0.Beta5//org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:189)
        at org.jb...@1.4.13.Final//org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1739)
        at org.jb...@1.4.13.Final//org.jboss.msc.service.ServiceControllerImpl$StartTask.execute(ServiceControllerImpl.java:1701)
        at org.jb...@1.4.13.Final//org.jboss.msc.service.ServiceControllerImpl$ControllerTask.run(ServiceControllerImpl.java:1559)
        at org.jbos...@2.4.0.Final//org.jboss.threads.ContextClassLoaderSavingRunnable.run(ContextClassLoaderSavingRunnable.java:35)
        at org.jbos...@2.4.0.Final//org.jboss.threads.EnhancedQueueExecutor.safeRun(EnhancedQueueExecutor.java:1990)
        at org.jbos...@2.4.0.Final//org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1486)
        at org.jbos...@2.4.0.Final//org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1377)
        at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: java.lang.NoClassDefFoundError: Failed to link org/h2/server/web/WebServlet (Module "com.h2database.h2" version 1.4.197 from local module loader @30c93896 (finder: local module finder @59a008ba (roots: D:\Documents\Mes Applications\DiveManager\wildfly-26.0.0.Beta1\modules,D:\Documents\Mes Applications\DiveManager\wildfly-26.0.0.Beta1\modules\system\layers\base))): javax/servlet/http/HttpServlet
        at java.base/java.lang.ClassLoader.defineClass1(Native Method)
        at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1012)
        at org.jboss.modules.ModuleClassLoader.doDefineOrLoadClass(ModuleClassLoader.java:350)
        at org.jboss.modules.ModuleClassLoader.defineClass(ModuleClassLoader.java:482)
        at org.jboss.modules.ModuleClassLoader.loadClassLocal(ModuleClassLoader.java:276)
        at org.jboss.modules.ModuleClassLoader$1.loadClassLocal(ModuleClassLoader.java:79)
        at org.jboss.modules.Module.loadModuleClass(Module.java:753)
        at org.jboss.modules.ModuleClassLoader.findClass(ModuleClassLoader.java:192)
        at org.jboss.modules.ConcurrentClassLoader.performLoadClassUnchecked(ConcurrentClassLoader.java:410)
        at org.jboss.modules.ConcurrentClassLoader.performLoadClass(ConcurrentClassLoader.java:398)
        at org.jboss.modules.ConcurrentClassLoader.loadClass(ConcurrentClassLoader.java:116)
        at org.jboss...@26.0.0.Beta1//org.jboss.as.jaxrs.deployment.JaxrsScanningProcessor.checkDeclaredApplicationClassAsServlet(JaxrsScanningProcessor.java:412)
        at org.jboss...@26.0.0.Beta1//org.jboss.as.jaxrs.deployment.JaxrsScanningProcessor.scanWebDeployment(JaxrsScanningProcessor.java:255)
        at org.jboss...@26.0.0.Beta1//org.jboss.as.jaxrs.deployment.JaxrsScanningProcessor.deploy(JaxrsScanningProcessor.java:105)
        at org.jboss...@18.0.0.Beta5//org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:182)
        ... 8 more

As I understand this error, the problerm  come from the class "javax.servlet.http.HttpServlet" witch is not in the classpath of the H2Console classloader.
This make me crazy because in th esame web.xml, I have another Servlet (javax.faces.webapp.FacesServlet) witch deploy correctly, and in cant imagine there is no need of the HttpServlet class in this servlet (by definition).

I believe there is some problem in the class path priority and the fact that the H2 librairy is loaded for the need of Wildlfy.

Can someone help me?

[Brian Stansberry]

This is likely because in https://issues.redhat.com/browse/WFLY-14814 we (deliberately) removed the H2 module's dependency on the javax.servlet.api module.

To restore support for this I suggest you do the following:

1) cd $WILDFLY_HOME

2) mkdir -p modules/javax/servlet/api/h2

3) In that dir create a 'module.xml' file with the following content:

<?xml version="1.0" encoding="UTF-8"?>

<module-alias xmlns="urn:jboss:module:1.9" name="javax.servlet.api:h2" target-name="javax.servlet.api"/>

Note that this won't work with WildFly Preview as H2 doesn't support the jakarta.* namespace.

There's more info on this at https://github.com/wildfly/wildfly/blob/main/ee-feature-pack/common/src/main/resources/modules/system/layers/base/com/h2database/h2/main/module.xml#L40

I filed https://issues.redhat.com/browse/WFLY-15814 to make sure I cover this point in the WF 26 Final release announcement.

I also filed https://issues.redhat.com/browse/WFLY-15815 to note this in the Datasource subsystem section of the Admin Guide, although I'm not sure if that will happen in the WF 26 docs.

[Benoit Delagarde]

Hello, 

The solution work fine in both Wildfly 25.0.1-Final and in Wildfly 26.0.0-Beta 1 

;-) 

Thank you. 

[Brian Stansberry]

Great; thanks for the question and the report that it works!