* e.g running mvn site:run will cause Jetty to fail.
     * </p>
     * <p>
     * The resolution is to add -Djava.net.preferIPv4Stack=true to the command line as documented in
     * http://cwiki.apache.org/confluence/display/MAVEN/ConnectException
     * </p>
     */
    @Test
    void testJdk7ipv6() {
        ConnectException connEx = new ConnectException("Connection refused: connect");

 The jar file is executable and provides a little tool to display how Maven parses and compares versions:

+----+
$ java -jar maven-artifact-*.jar 3.2.4-alpha-1 3.2.4-SNAPSHOT 3.2.4.0
Display parameters as parsed by Maven (in canonical form) and comparison result:
1. 3.2.4-alpha-1 == 3.2.4.alpha.1
   3.2.4-alpha-1 < 3.2.4-SNAPSHOT

ClassNotFoundExcepti; public abstract java.net.URL getResource(String); public abstract java.util.Enumeration findResources(String) throws java.io.IOException; public abstract java.io.InputStream getResourceAsStream(String); public abstract void display(); } org/codehaus/classworlds/ClassRealmAdapter.class package org.codehaus.classworlds; public synchronized class ClassRealmAdapter implements ClassRealm { private static java.util.HashMap instances; private org.codehaus.plexus.classworlds.realm.ClassRealm...

 Plugins should avoid these classes and be updated to use only Maven3 dependencies (and require Maven3): see
 {{{https://cwiki.apache.org/confluence/display/MAVEN/Plugin+migration+to+Maven3+dependencies} Plugin migration to Maven3 dependencies}}

                        + pluginDescriptor.getId() + "'. A required class is missing: "
                        + cause.getMessage());
                pluginRealm.display(ps);

                throw new PluginContainerException(mojoDescriptor, pluginRealm, os.toString(), cause);
            } else if (cause instanceof LinkageError) {

      this License, each Contributor hereby grants to You a perpetual,
      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
      copyright license to reproduce, prepare Derivative Works of,
      publicly display, publicly perform, sublicense, and distribute the
      Work and such Derivative Works in Source or Object form.

   3. Grant of Patent License. Subject to the terms and conditions of

ClassNotFoundExcepti; public abstract java.net.URL getResource(String); public abstract java.util.Enumeration findResources(String) throws java.io.IOException; public abstract java.io.InputStream getResourceAsStream(String); public abstract void display(); } org/codehaus/classworlds/ClassRealmAdapter.class package org.codehaus.classworlds; public synchronized class ClassRealmAdapter implements ClassRealm { private static java.util.HashMap instances; private org.codehaus.plexus.classworlds.realm.ClassRealm...

        // The exception stack trace is not really interesting here
        // but the message itself may be quite details and span multiple
        // lines with errors in it, so only display it at debug level.
        String msg = "The POM for {} is invalid, transitive dependencies (if any) will not be available: {}";
        if (logger.isDebugEnabled()) {

[dev-ml-list]: https://maven.apache.org/mailing-lists.html
[code-style]: https://maven.apache.org/developers/conventions/code.html
[cla]: https://www.apache.org/licenses/#clas
[maven-wiki]: https://cwiki.apache.org/confluence/display/MAVEN/Index

            PrintStream ps = new PrintStream(os);
            ps.println(
                    "A required class was missing while executing " + mojoDescriptor.getId() + ": " + e.getMessage());
            pluginRealm.display(ps);
            Exception wrapper = new PluginContainerException(mojoDescriptor, pluginRealm, os.toString(), e);
            throw new PluginExecutionException(mojoExecution, project, wrapper);
        } catch (LinkageError e) {