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https://issues.apache.org/jira/browse/OWB-629?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13153524#comment-13153524
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Christian Kaltepoth commented on OWB-629:
-----------------------------------------
I've created a first simple version of a patch for this issue. Please note that
it is more or less a quickfix. But it works fine. :)
Let me first explain what Weld does to prevent such problems. Weld creates one
"WeldClassImpl" object for every class it finds. This object holds all
information of a class like it's fields, methods, constructors and so on. All
the reflection is done in the constructor of WeldClassImpl. If some of the
reflection code fails (due to a NoClassDefFoundError for example) an info
message is created in the logs and the class is ignored for the deployment.
My first try to fix this issue in OWB was to simply catch NoClassDefFoundError
when loading the class. Unfortunately this was not enough. It seems like in
some cases loading the class works fine but later when getDeclaredFields() is
called similar exceptions are thrown. Weld doesn't suffer from these issues as
all reflection is done initially for the class when creating WeldClassImpl.
My patch does the following. It tries to load the class using
ClassUtil.getClassFromName(). If this succeeds it invokes getDeclaredFields()
and getDeclaredFields(). This is done just to provoke a NoClassDefFoundError if
some dependencies of the class are missing. If an exception is thrown, a
warning is created in the logs and the class is ignored.
I know this is probably a quickfix. There are definitively nicer ways to do it.
But it seems to work fine. I was able to deploy an application that includes
Seam Persistence and Seam Faces without any issues which wasn't the case with
plain 1.1.2.
I hope my explanations helps a bit! :)
> NoClassDefFoundError for optional dependencies
> ----------------------------------------------
>
> Key: OWB-629
> URL: https://issues.apache.org/jira/browse/OWB-629
> Project: OpenWebBeans
> Issue Type: Bug
> Components: Core
> Affects Versions: 1.1.2
> Environment: Tomcat 7.0.22, JDK 1.6.0_23
> Reporter: Christian Kaltepoth
> Assignee: Gurkan Erdogdu
> Attachments: owb-test-updated.zip, owb-test.zip
>
>
> Some of the Seam modules (like Seam Persistence) contain optional Maven
> dependencies. The persistence module for example declares Hibernate as an
> provided dependency. The Seam Persistence module contains only one single
> class that requires Hibernate which is an SPI implementation to support
> specific Hibernate features. This class is only loaded/used if Hibernate is
> detected. Furthermore it's important to know that this bean is not meant to
> be a bean manged by the CDI runtime. Therefore it is annotated with @Veto
> (Seam Solder API) to get vetoed during CDI startup.
> All this works very fine with Weld 1.1.x. Unfortunately OWB fails to deploy
> the Seam Persistence JAR with the following exception:
> SCHWERWIEGEND: Exception sending context initialized event to listener
> instance of class org.apache.webbeans.servlet.WebBeansConfigurationListener
> java.lang.NoClassDefFoundError: org/hibernate/TransientObjectException
> at java.lang.Class.forName0(Native Method)
> at java.lang.Class.forName(Class.java:264)
> at
> org.apache.webbeans.util.ClassUtil.getClassFromName(ClassUtil.java:115)
> at
> org.apache.webbeans.corespi.scanner.AbstractMetaDataDiscovery.getBeanClasses(AbstractMetaDataDiscovery.java:209)
> at
> org.apache.webbeans.config.BeansDeployer.checkStereoTypes(BeansDeployer.java:732)
> at
> org.apache.webbeans.config.BeansDeployer.deploy(BeansDeployer.java:160)
> at
> org.apache.webbeans.lifecycle.AbstractLifeCycle.startApplication(AbstractLifeCycle.java:127)
> at
> org.apache.webbeans.web.lifecycle.WebContainerLifecycle.startApplication(WebContainerLifecycle.java:88)
> at
> org.apache.webbeans.servlet.WebBeansConfigurationListener.contextInitialized(WebBeansConfigurationListener.java:85)
> at
> org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4723)
> at
> org.apache.catalina.core.StandardContext$1.call(StandardContext.java:5226)
> at
> org.apache.catalina.core.StandardContext$1.call(StandardContext.java:5221)
> at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
> at java.util.concurrent.FutureTask.run(FutureTask.java:166)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
> at java.lang.Thread.run(Thread.java:679)
> Caused by: java.lang.ClassNotFoundException:
> org.hibernate.TransientObjectException
> at
> org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1678)
> at
> org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1523)
> ... 17 more
> For me it looks like the class scanner tries to build a set of Class objects
> from all classes in the bean archive. But this fails as soon as the class
> compiled against the Hibernate API is picked up as Hibernate is not on the
> classpath.
> If I remember correctly Weld 1.0.x had similar issues. Somehow this was
> resolved in Weld 1.1.x but I don't know anything about the details.
> I think OWB could handle NoClassDefFoundErrors a bit nicer. Currently OWB
> doesn't support bean archives that have optional dependencies at all. So an
> archive that contains just one class for which not all dependencies (classes)
> are accessible from the ClassLoader completely fails to deploy using OWB.
> Even if this class isn't used at all (neither within CDI nor manually
> instantiated in the application code).
> I think it would be easy to fix this. ClassUtil.getClassFromName() or
> AbstractMetaDataDiscovery.getBeanClasses() could catch NoClassDefFoundError
> and handles them in some way. I think it would make sense to simply ignore
> such errors during the bean archive scanning process on continue with the
> next class.
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