title: An API incompatibility was encountered while executing org.apache.maven.plugins:maven-shade-plugin:1.3.1:shade: java.lang.AbstractMethodError: null
body: <p>While trying to build an old version of Apache CXF 2.2.2, I kept getting an error produced by an <strong>XmlAppendingTransformer</strong> used by the <strong>maven-shade-plugin</strong>: unable to connect to get the DTD for <a href="http://java.sun.com/dtd/properties.dtd" rel="nofollow">http://java.sun.com/dtd/properties.dtd</a> (referenced by the file <strong>META-INF/cxf/extensions.xml</strong>)</p>
  
  <p>I have tried to fix this problem by using the <strong><em>ignoreDtd</em></strong> option provided by maven-shade-plugin starting with version 1.3.1.</p>
  
  <p>But now I am getting another more weird error:</p>
  
  <pre><code>[ERROR] Failed to execute goal org.apache.maven.plugins:maven-shade-plugin:1.3.1:shade (default) on project cxf-bundle: Execution default of goal org.apache.maven.plugins:maven-shade-plugin:1.3.1:shade failed: An API incompatibility was encountered while executing org.apache.maven.plugins:maven-shade-plugin:1.3.1:shade: java.lang.AbstractMethodError: null
  [ERROR] -----------------------------------------------------
  [ERROR] realm =    plugin&gt;org.apache.maven.plugins:maven-shade-plugin:1.3.1
  [ERROR] strategy = org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy
  [ERROR] urls[0] = file:/C:/Users/postese/.m2/repository/org/apache/maven/plugins/maven-shade-plugin/1.3.1/maven-shade-plugin-1.3.1.jar
  [ERROR] urls[1] = file:/C:/Users/postese/libraries/apache-cxf-2.2.2-patched-src/buildtools/target/cxf-buildtools-2.2.2.jar
  [ERROR] urls[2] = file:/C:/Users/postese/.m2/repository/pmd/pmd/4.2/pmd-4.2.jar
  [ERROR] urls[3] = file:/C:/Users/postese/.m2/repository/ant/ant/1.6/ant-1.6.jar
  [ERROR] urls[4] = file:/C:/Users/postese/.m2/repository/junit/junit/3.8.1/junit-3.8.1.jar
  [ERROR] urls[5] = file:/C:/Users/postese/.m2/repository/org/codehaus/plexus/plexus-utils/1.5.5/plexus-utils-1.5.5.jar
  [ERROR] urls[6] = file:/C:/Users/postese/.m2/repository/asm/asm/3.2/asm-3.2.jar
  [ERROR] urls[7] = file:/C:/Users/postese/.m2/repository/asm/asm-commons/3.2/asm-commons-3.2.jar
  [ERROR] urls[8] = file:/C:/Users/postese/.m2/repository/asm/asm-tree/3.2/asm-tree-3.2.jar
  [ERROR] urls[9] = file:/C:/Users/postese/.m2/repository/org/jdom/jdom/1.1/jdom-1.1.jar
  [ERROR] urls[10] = file:/C:/Users/postese/.m2/repository/org/apache/maven/shared/maven-dependency-tree/1.1/maven-dependency-tree-1.1.jar
  [ERROR] Number of foreign imports: 1
  [ERROR] import: Entry[import  from realm ClassRealm[project&gt;org.apache.cxf:cxf-bundle:2.2.2, parent: ClassRealm[maven.api, parent: null]]]
  [ERROR]
  [ERROR] -----------------------------------------------------
  </code></pre>
  
  <p>Which library or plugin is causing the "API incompatibility" ?</p>