Embedding Dependency in JAR with maven-bundle-plugin not working

Question

I'm suceeded with adding OSGi specific meta-data to the MANIFEST of the flying-saucer-pdf Maven artifact. However, I do not succeed with embedding the dependencies and transitive dependencies of that artifact into the created JAR file.

I was using the original sources from flying-saucer-pdf taken from GitHub [1] and added the following statements to the pom.xml file:

<plugin>
    <artifactId>maven-jar-plugin</artifactId>
    <configuration>
      <archive>
        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
      </archive>
    </configuration>
  </plugin>
  <plugin>
    <groupId>org.apache.felix</groupId>
    <artifactId>maven-bundle-plugin</artifactId>
    <executions>
      <execution>
        <id>bundle-manifest</id>
        <phase>process-classes</phase>
        <goals>
          <goal>manifest</goal>
        </goals>
        <configuration>
          <instructions>
            <Embed-Dependency>itext</Embed-Dependency>
            <Embed-Transitive>true</Embed-Transitive>
          </instructions>
        </configuration>
      </execution>
    </executions>
  </plugin>

The artifact has a dependency declared to itext version 2.1.7 in its original pom.xml which I did not touch. I also did not mess with the original packaging type of the artifact which is jar.

Unfortunately, this does only part of the work. The MANIFEST.MF seems correct and contains the expected OSGi tags:

Manifest-Version: 1.0
Bundle-Description: Flying Saucer is a CSS 2.1 renderer written in Jav
 a.  This artifact supports PDF output.
Bundle-License: http://www.gnu.org/licenses/lgpl.html
Bundle-SymbolicName: org.xhtmlrenderer.flying-saucer-pdf
Archiver-Version: Plexus Archiver
Built-By: u0400072
Bnd-LastModified: 1478168053263
Bundle-ManifestVersion: 2
Embed-Dependency: itext
Import-Package: com.apple.mrj,com.lowagie.toolbox,javax.crypto,javax.i
 mageio,javax.imageio.metadata,javax.imageio.plugins.jpeg,javax.imagei
 o.stream,javax.swing,javax.xml.parsers,javax.xml.transform,javax.xml.
 transform.dom,javax.xml.transform.sax,javax.xml.transform.stream,org.
 bouncycastle.asn1,org.bouncycastle.asn1.cmp,org.bouncycastle.asn1.cms
 ,org.bouncycastle.asn1.ocsp,org.bouncycastle.asn1.pkcs,org.bouncycast
 le.asn1.tsp,org.bouncycastle.asn1.x509,org.bouncycastle.cms,org.bounc
 ycastle.crypto,org.bouncycastle.crypto.engines,org.bouncycastle.crypt
 o.modes,org.bouncycastle.crypto.paddings,org.bouncycastle.crypto.para
 ms,org.bouncycastle.jce.provider,org.bouncycastle.ocsp,org.bouncycast
 le.tsp,org.w3c.dom,org.xhtmlrenderer.context,org.xhtmlrenderer.css.co
 nstants,org.xhtmlrenderer.css.extend,org.xhtmlrenderer.css.parser,org
 .xhtmlrenderer.css.sheet,org.xhtmlrenderer.css.style,org.xhtmlrendere
 r.css.style.derived,org.xhtmlrenderer.css.value,org.xhtmlrenderer.ext
 end,org.xhtmlrenderer.layout,org.xhtmlrenderer.render,org.xhtmlrender
 er.resource,org.xhtmlrenderer.simple.extend,org.xhtmlrenderer.swing,o
 rg.xhtmlrenderer.util,org.xml.sax,org.xml.sax.helpers
Require-Capability: osgi.ee;filter:="(&(osgi.ee=JavaSE)(version=1.6))"
Tool: Bnd-3.2.0.201605172007
Embedded-Artifacts: itext-2.1.7.jar;g="com.lowagie";a="itext";v="2.1.7
 "
Export-Package: org.xhtmlrenderer.pdf;uses:="org.w3c.dom,org.xhtmlrend
 erer.css.constants,org.xhtmlrenderer.css.parser,org.xhtmlrenderer.css
 .style,org.xhtmlrenderer.css.value,org.xhtmlrenderer.extend,org.xhtml
 renderer.layout,org.xhtmlrenderer.render,org.xhtmlrenderer.resource,o
 rg.xhtmlrenderer.simple.extend,org.xhtmlrenderer.swing,org.xml.sax";v
 ersion="9.0.10",org.xhtmlrenderer.pdf.util;uses:="org.w3c.dom,org.xht
 mlrenderer.pdf";version="9.0.10",org.xhtmlrenderer.simple;uses:="java
 x.swing,org.w3c.dom,org.xhtmlrenderer.css.extend,org.xhtmlrenderer.cs
 s.sheet,org.xhtmlrenderer.extend,org.xhtmlrenderer.layout,org.xhtmlre
 nderer.swing,org.xhtmlrenderer.util";version="9.0.10"
Bundle-Name: Flying Saucer PDF Rendering
Bundle-Version: 9.0.10.SNAPSHOT
Bundle-ClassPath: .,itext-2.1.7.jar
Embed-Transitive: true
Created-By: Apache Maven Bundle Plugin
Build-Jdk: 1.8.0_102

But the itext library is not put into the resulting JAR, i.e. the Bundle-ClassPath entry of the MANIFEST points to a missing content.

In addition I tried to create an entirely new artifact which declares a dependency to the original flying-saucer-pdf artifact and re-bundles it as an OSGi bundle flowing this answer [2] here on StackOverflow and this worked.

The only real difference that I can see is the packaging type 'bundle' vs. 'jar'. But I cannot change that packaging type in the original flying-saucer-pdf artifact since everything needs to stay as is for non-OSGi-usages in order to get that change accepted as a Push Request.

Do you guys know if this embedding dependencies with the maven-bundle-plugin can actually work with the packaging type 'jar'? Or does it need the packaging type 'bundle'?

I appreciate any response and hint of what I could try to get that re-bundling done directly within the original artifact.

Thank you very much.

Regards Timo Rohrberg

Answer 1

There are two ways to use the maven bundle plugin.

The first way is to use

<extensions>true</extensions> and <packaging>bundle</packaging>

In this case the maven bundle plugin is in charge of all build steps and can influence the jar file contents.

The second way is to use the manifest goal and add the manifest in the jar plugin. In this case maven bundle plugin can only influence the jar. It can not embed any other library or copy over external private classes.

So if you need embedding then the only way is to change the packaging.

So I think there are two solutions that do not influence the original jar too much.

1. Do not embed and install the dependencies as bundles
2. Create a spearate module in the build to create a bundle that is then available additionally to the original jar