There are some standard JDK APIs that are not part of the mapreduce.job.classloader.system.classes property value.
Currently the default value covers only "java.,javax." from the JDK. However, there are other APIs that are as well-established as these, such as org.w3c.dom and org.xml.sax. In other similar systems (e.g. OSGi), it is a standard practice to include both of these packages in the system classes. We should add these to the default values.