HOWTO: Use Maven, Ant, and XSLT to scrub unwanted p2 metadata from an update site

Some time ago, I wrote about Using p2.inf to add/remove update sites. Tonight I found a simpler way to remove references in p2 metadata to external 3rd party sites.

For example, say you're repackaging some 3rd party features onto your own site, but don't want those features to provide references to the vendor's own update sites because you want to ensure that your product's site will only result in your sanctioned version being installed.

When you generate an update site, p2 pulls the information in the included features and will result in a section of references in the site's metadata that looks like this:

  <references size="6">
    <repository uri="http://download.eclipse.org/egit/updates" url="http://download.eclipse.org/egit/updates" type="0" options="0"/>
    <repository uri="http://subclipse.tigris.org/update_1.6.x" url="http://subclipse.tigris.org/update_1.6.x" type="1" options="0"/>
    <repository uri="http://download.eclipse.org/egit/updates" url="http://download.eclipse.org/egit/updates" type="1" options="0"/>
    <repository uri="http://subclipse.tigris.org/update_1.6.x" url="http://subclipse.tigris.org/update_1.6.x" type="0" options="0"/>
    <repository uri="http://eclipse.svnkit.com/1.3.x/" url="http://eclipse.svnkit.com/1.3.x/" type="0" options="0"/>
    <repository uri="http://eclipse.svnkit.com/1.3.x/" url="http://eclipse.svnkit.com/1.3.x/" type="1" options="0"/>
  </references>

To remove that, you can play with p2.inf directives, or you can simply perform an XSL transformation on the generated content.xml (inside content.jar, if your metadata is compressed) to remove the <references/> node:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0">
<xsl:template match="/">
        <xsl:apply-templates select="*"/>
</xsl:template>
<xsl:template match="*">
        <xsl:copy >
                <xsl:for-each select="@*">
                        <xsl:copy />
                </xsl:for-each>
                <xsl:apply-templates />
        </xsl:copy>
</xsl:template>
<xsl:template match="references" />
</xsl:stylesheet>

If you're generating your update site w/ Tycho, this transform can be called via a simple Ant script:

       <target name="remove.references">
                <!-- requires ant-contrib only if you like using if-then-else structures -->
                <if>
                        <available file="${update.site.source.dir}/content.jar" type="file" />
                        <then>
                                <unzip src="${update.site.source.dir}/content.jar" dest="${update.site.source.dir}" />
                                <delete file="${update.site.source.dir}/content.jar" />
                        </then>
                </if>
                <copy file="${update.site.source.dir}/content.xml" tofile="${update.site.source.dir}/content.old.xml" overwrite="true" />
                <xslt style="remove-references.xsl" in="${update.site.source.dir}/content.old.xml" out="${update.site.source.dir}/content.xml" />
                <zip destfile="${update.site.source.dir}/content.jar" basedir="${update.site.source.dir}" includes="content.xml" />
                <delete file="${update.site.source.dir}/content.xml" />
                <delete file="${update.site.source.dir}/content.old.xml" />
        </target>

Then, in your site's pom.xml, to call the Ant script, do this:

       <build>
                <plugins>
                        <plugin>
                                <groupId>org.apache.maven.plugins</groupId>
                                <artifactId>maven-antrun-plugin</artifactId>
                                <!-- make sure this variable is defined, eg., set to 1.3 -->
                                <version>${maven.antrun.plugin.version}</version>
                                <executions>
                                        <execution>
                                                <id>install</id>
                                                <phase>install</phase>
                                                <configuration>
                                                        <quiet>true</quiet>
                                                        <tasks>
                                                                <!-- called AFTER generating update site + zip to tweak content -->
                                                                <ant antfile="build.xml">
                                                                        <property name="SOME_ANT_VARIABLE" value="${SOME_MAVEN_VARIABLE}" />
                                                                </ant>
                                                        </tasks>
                                                </configuration>
                                                <goals>
                                                        <goal>run</goal>
                                                </goals>
                                        </execution>
                                </executions>
                                <dependencies>
                                        <!-- some dependencies your ant script might need -->
                                        <dependency>
                                                <groupId>commons-net</groupId>
                                                <artifactId>commons-net</artifactId>
                                                <version>1.4.1</version>
                                        </dependency>
                                        <dependency>
                                                <groupId>org.apache.ant</groupId>
                                                <artifactId>ant</artifactId>
                                                <version>1.7.1</version>
                                        </dependency>
                                        <dependency>
                                                <groupId>org.apache.ant</groupId>
                                                <artifactId>ant-nodeps</artifactId>
                                                <version>1.7.1</version>
                                        </dependency>
                                        <dependency>
                                                <groupId>org.apache.ant</groupId>
                                                <artifactId>ant-trax</artifactId>
                                                <version>1.7.1</version>
                                        </dependency>
                                        <dependency>
                                                <groupId>org.apache.ant</groupId>
                                                <artifactId>ant-commons-net</artifactId>
                                                <version>1.7.1</version>
                                        </dependency>
                                        <dependency>
                                                <groupId>org.apache.ant</groupId>
                                                <artifactId>ant-apache-regexp</artifactId>
                                                <version>1.7.1</version>
                                        </dependency>
                                        <dependency>
                                                <groupId>ant-contrib</groupId>
                                                <artifactId>ant-contrib</artifactId>
                                                <version>1.0b3</version>
                                        </dependency>
                                </dependencies>
                        </plugin>
                </plugins>
        </build>

I suppose there's probably a way to call a transform directly from Maven w/o the Ant wrapper, but this allows unpacking and repacking of the content.jar to get at the content.xml file.