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http://jira.codehaus.org/browse/MNG-4207?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=180741#action_180741
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John Casey commented on MNG-4207:
---------------------------------
The problem is in the way the commons-logging API discovers which logging
framework to delegate to. Commons-logging is used by httpclient, which is used
by the non-lightweight http wagon. The first thing clogging checks for is the
presence of the Log4J classes, and if it finds them, it tries to load them
preferentially over the other logging frameworks. If a plugin depends on log4j,
it seems like this can confuse clogging into thinking Maven's core has access
to these classes - probably because clogging is using the Thread context
classloader to discover the log4j classes - which in turn leads commons-logging
to throw an exception when it tries to instantiate log4j (commons-logging in
this case is loaded from shaded classes that are in the Maven core). Including
- and shading - log4j into the Maven core seems to solve this problem by making
the classes available in the correct classloader.
> Plugins that use ArtifactResolver with http repositories AND depend on log4j
> run into ExceptionInInitializerError
> -----------------------------------------------------------------------------------------------------------------
>
> Key: MNG-4207
> URL: http://jira.codehaus.org/browse/MNG-4207
> Project: Maven 2
> Issue Type: Bug
> Components: Artifacts and Repositories, Class Loading
> Affects Versions: 2.2.0
> Reporter: John Casey
> Assignee: John Casey
> Priority: Blocker
> Fix For: 2.2.0
>
> Attachments: maven-it-plugin-log4j.zip, pom.xml
>
>
> plugins that use log4j as a dependency and that also resolve artifacts using
> the ArtifactResolver to access one or more http repositories are running into
> a stacktrace as follows:
> {noformat}
> [FATAL ERROR] org.apache.maven.plugin.coreit.ItMojo#execute() caused a
> linkage error (java.lang.ExceptionInInitializerError) and may be out-of-date.
> Check the realms:
> [FATAL ERROR] Plugin realm =
> app0.child-container[org.apache.maven.its.plugins:maven-it-plugin-log4j:2.1-SNAPSHOT]
> urls[0] =
> file:/Users/jdcasey/.m2/repository/org/apache/maven/its/plugins/maven-it-plugin-log4j/2.1-SNAPSHOT/maven-it-plugin-log4j-2.1-SNAPSHOT.jar
> urls[1] =
> file:/Users/jdcasey/.m2/repository/org/codehaus/plexus/plexus-utils/1.1/plexus-utils-1.1.jar
> urls[2] =
> file:/Users/jdcasey/.m2/repository/log4j/log4j/1.2.14/log4j-1.2.14.jar
> [FATAL ERROR] Container realm = plexus.core
> urls[0] =
> file:/Users/jdcasey/apps/maven/apache-maven-2.2.0-RC3-SNAPSHOT/lib/maven-2.2.0-RC3-SNAPSHOT-uber.jar
> [INFO]
> ------------------------------------------------------------------------
> [ERROR] FATAL ERROR
> [INFO]
> ------------------------------------------------------------------------
> [INFO] null
> org/apache/log4j/Category
> [INFO]
> ------------------------------------------------------------------------
> [DEBUG] Trace
> java.lang.ExceptionInInitializerError
> at
> org.apache.maven.wagon.shared.http.AbstractHttpClientWagon.openConnectionInternal(AbstractHttpClientWagon.java:153)
> at
> org.apache.maven.wagon.AbstractWagon.openConnection(AbstractWagon.java:105)
> at
> org.apache.maven.wagon.AbstractWagon.connect(AbstractWagon.java:207)
> at
> org.apache.maven.artifact.manager.DefaultWagonManager.getRemoteFile(DefaultWagonManager.java:439)
> at
> org.apache.maven.artifact.manager.DefaultWagonManager.getArtifact(DefaultWagonManager.java:372)
> at
> org.apache.maven.artifact.manager.DefaultWagonManager.getArtifact(DefaultWagonManager.java:327)
> at
> org.apache.maven.artifact.resolver.DefaultArtifactResolver.resolve(DefaultArtifactResolver.java:216)
> at
> org.apache.maven.artifact.resolver.DefaultArtifactResolver.resolve(DefaultArtifactResolver.java:90)
> at org.apache.maven.plugin.coreit.ItMojo.execute(ItMojo.java:97)
> at
> org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:483)
> at
> org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:678)
> at
> org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalWithLifecycle(DefaultLifecycleExecutor.java:540)
> at
> org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:519)
> at
> org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:371)
> at
> org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:332)
> at
> org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:181)
> at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:356)
> at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:137)
> at org.apache.maven.cli.MavenCli.main(MavenCli.java:362)
> at
> org.apache.maven.cli.compat.CompatibleMain.main(CompatibleMain.java:41)
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:585)
> at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315)
> at org.codehaus.classworlds.Launcher.launch(Launcher.java:255)
> at
> org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430)
> at org.codehaus.classworlds.Launcher.main(Launcher.java:375)
> Caused by: hidden.org.apache.commons.logging.LogConfigurationException:
> hidden.org.apache.commons.logging.LogConfigurationException: No suitable
> Log constructor [Ljava.lang.Class;@986c47 for
> hidden.org.apache.commons.logging.impl.Log4JLogger (Caused by
> java.lang.NoClassDefFoundError: org/apache/log4j/Category)
> (Caused by hidden.org.apache.commons.logging.LogConfigurationException:
> No suitable Log constructor [Ljava.lang.Class;@986c47
> for hidden.org.apache.commons.logging.impl.Log4JLogger (Caused by
> java.lang.NoClassDefFoundError: org/apache/log4j/Category))
> at
> hidden.org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:543)
> at
> hidden.org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:235)
> at
> hidden.org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:209)
> at
> hidden.org.apache.commons.logging.LogFactory.getLog(LogFactory.java:351)
> at
> hidden.org.apache.commons.httpclient.HttpClient.<clinit>(HttpClient.java:66)
> ... 28 more
> Caused by: hidden.org.apache.commons.logging.LogConfigurationException: No
> suitable Log constructor [Ljava.lang.Class;@986c47
> for hidden.org.apache.commons.logging.impl.Log4JLogger (Caused by
> java.lang.NoClassDefFoundError: org/apache/log4j/Category)
> at
> hidden.org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:413)
> at
> hidden.org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:529)
> ... 32 more
> Caused by: java.lang.NoClassDefFoundError: org/apache/log4j/Category
> at java.lang.Class.getDeclaredConstructors0(Native Method)
> at java.lang.Class.privateGetDeclaredConstructors(Class.java:2357)
> at java.lang.Class.getConstructor0(Class.java:2671)
> at java.lang.Class.getConstructor(Class.java:1629)
> at
> hidden.org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:410)
> ... 33 more
> {noformat}
> The problem seems to come from some sort of conflict between the dependencies
> of httpclient, which is now included in the Maven core as part of the
> non-lightweight http wagon, and other users of log4j (plugins, mainly). Still
> tracking down the exact cause of the problem, trying to determine how best to
> fix it. I'm including Benjamin Bentmann's original test case for this issue,
> since he's the one who has done most of the legwork at this point.
> instructions for the attached files (maven-it-plugin-log4j.zip and pom.xml):
> 1. unpack and install the IT plugin using Maven
> 2. Using the attached pom.xml as the project POM, try `mvn initialize -X`
> 3. observe the stacktrace that results.
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