1)

A bug was inserted when the patch for XMLRPC-116 was changed/refactored slightly.

In handleInitParameters you call ReflectionUtil.setProperty(server, name, value) where server is an XmlRpcServletServer . This class does not have any setters for init parameters such as "enabledForExtensions" or "contentLengthOptional", so reflection fails. I believe that methods on XmlRpcServerConfig are reflection should be used on (this is what I did in my patch) and therefore

ReflectionUtil.setProperty(server, name, value)

should change to

ReflectionUtil.setProperty(server.getConfig(), name, value).

2)

The latter issue was due to voidMethodEnabled not being set (here: to true) using isEnabledForExtension prior to public method being registered and therefore
XmlRpcServlet.newPropertyHandlerMapping:~180

should change to

        mapping.setVoidMethodEnabled(server.getConfig().isEnabledForExtensions());
        mapping.load(Thread.currentThread().getContextClassLoader(), url);

from

        mapping.load(Thread.currentThread().getContextClassLoader(), url);
        mapping.setVoidMethodEnabled(server.getConfig().isEnabledForExtensions());