It will be interesting to see if there is a significant speed increase, as it will be nice to reduce the time of our main nightly build which usually takes about 90-95 minutes.

Luckily, Hudson / Jenkins makes it easy to test out running builds using different versions of Maven, so there is no reason not to test it out. Remember that the reporting has changed significantly in Maven 3, so while your project may build successfully in Maven 3 without any changes to the pom, you will need to make changes to get the reporting working. This article on the Maven Site Plugin explains the changes and shows an example of the new configuration.

org.apache.xerces.impl.dv.DVFactoryException:
DTD factory class org.apache.xerces.impl.dv.dtd.DTDDVFactoryImpl does not extend from DTDDVFactory.

This basically meant that an incompatible version of xerces was trying to be run. We have everything set to use Java 1.6, which ships with its own version of xerces. After some debugging, it was tracked down to the maven-site-plugin which we had recently upgraded to use version 2.1 of the plugin by specifying it in our pom file like so:

<pluginManagement>
	<plugins>
		<plugin>
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-site-plugin</artifactId>
			<version>2.1</version>
		</plugin>
	</plugins>
</pluginManagement>

The maven-site-site plugin has the following dependency structure:

• org.apache.maven.plugins:maven-site-plugin:maven-plugin:2.1
  • org.apache.maven.doxia:doxia-module-xhtml:jar:1.1.2 (compile)
    • org.apache.maven.doxia:doxia-core:jar:1.1.2 (compile)
      • xerces:xercesImpl:jar:2.8.1 (compile)

It is the dependency of the xercesImpl jar 2.8.1 that is the problem. To get around this issue, you can tell the maven-site-plugin to exclude a particular dependency. This can be done like so:

<pluginManagement>
	<plugins>
		<plugin>
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-site-plugin</artifactId>
			<version>2.1</version>
			<dependencies>
				<dependency>
					<groupId>org.apache.maven.doxia</groupId>
					<artifactId>doxia-core</artifactId>
					<version>1.1.2</version>
					<exclusions>
						<exclusion>
							<groupId>xerces</groupId>
							<artifactId>xercesImpl</artifactId>
						</exclusion>
					</exclusions>
				</dependency>
			</dependencies>
		</plugin>
	</plugins>
</pluginManagement>

There are a couple of maven reporting plugins that we found produced this exception when run with maven-site-plugin 2.1. These plugins are:

• DocFlex/XML Maven Plugin
• Canoo Webtest Maven Plugin

If you use an older version of the maven-site-plugin then the above mentioned reporting plugins should work ok. It is only when specifying a version of 2.1 or above that the exception occurs.

Some of the solutions suggested on the net didn’t work for us, like adding the xercesImpl jar as a dependency to the actual reporting plugin in question, so hopefully the solution mentioned in this post is helpful.