NullPointerException org.apache.commons.digester.Digester.getXMLReader(Digester.java:1058)

Maven is great build tool making it easy to fetch all the library dependencies for a particular build. But what happens when you've got an application that uses wide variety of libraries of which can be dependent on the same library but different versions. Indeed we can have conflicts and the title of this blog is what I got as a result of some transitive dependency of Apache CXF.

The root cause of the above error is because an older version of the SAXParserFactory was being used. The class loaders for commons digester was using the SAXParserFactory from another JAR file in the classpath rather than the one provided in the JDK 1.6.
Others have had similar problems as in this forum


It turns out I had ther xercesImpl-2.6.2 in my classpath. This I needed to remove and boilied down to adding exclusions in my POM file as follows:

    <!-- 
    ========================
    Apache CXF Web services
    ========================
    -->
    <dependency>
        <groupId>org.apache.cxf</groupId>
        <artifactId>cxf-bundle-minimal</artifactId>
        <version>2.2.4</version>
        
        <exclusions>
            <exclusion>
                <groupId>xalan</groupId>                
                <artifactId>xalan</artifactId>
            </exclusion>
            <exclusion>
                <groupId>xalan</groupId>                
                <artifactId>serializer</artifactId>
            </exclusion>

            <exclusion>
                <groupId>xom</groupId>
                <artifactId>xom</artifactId>
            </exclusion>        

            <exclusion>
                <groupId>xerces</groupId>
                <artifactId>xerces</artifactId>
            </exclusion>

            <exclusion>
                <groupId>xerces</groupId>
                <artifactId>xercesImpl</artifactId>
            </exclusion>

            <exclusion>
                <groupId>xerces</groupId>
                <artifactId>xmlParserAPIs</artifactId>
            </exclusion>
            
            <exclusion>
                <groupId>org.apache.santuario</groupId>
                <artifactId>xmlsec</artifactId>
            </exclusion>            
            
        </exclusions>        
        
    </dependency>