Erro 500 em EmpresasService utilizando XML | Java Servlet: autenticação, autorização e o padrão MVC

HTTP Status 500 – Internal Server Error
Type Exception Report

Message Servlet execution threw an exception

Description The server encountered an unexpected condition that prevented it from fulfilling the request.

Exception

javax.servlet.ServletException: Servlet execution threw an exception
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
Root Cause

java.lang.ExceptionInInitializerError
    com.thoughtworks.xstream.XStream.setupConverters(XStream.java:1002)
    com.thoughtworks.xstream.XStream.<init>(XStream.java:592)
    com.thoughtworks.xstream.XStream.<init>(XStream.java:514)
    com.thoughtworks.xstream.XStream.<init>(XStream.java:483)
    com.thoughtworks.xstream.XStream.<init>(XStream.java:429)
    com.thoughtworks.xstream.XStream.<init>(XStream.java:368)
    br.com.mmb.gerenciador.servlet.EmpresasService.service(EmpresasService.java:36)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
Root Cause

java.lang.reflect.InaccessibleObjectException: Unable to make field protected java.lang.reflect.InvocationHandler java.lang.reflect.Proxy.h accessible: module java.base does not "opens java.lang.reflect" to unnamed module @661b3ea4
    java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354)
    java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297)
    java.base/java.lang.reflect.Field.checkCanSetAccessible(Field.java:178)
    java.base/java.lang.reflect.Field.setAccessible(Field.java:172)
    com.thoughtworks.xstream.core.util.Fields.locate(Fields.java:40)
    com.thoughtworks.xstream.converters.extended.DynamicProxyConverter.<clinit>(DynamicProxyConverter.java:42)
    com.thoughtworks.xstream.XStream.setupConverters(XStream.java:1002)
    com.thoughtworks.xstream.XStream.<init>(XStream.java:592)
    com.thoughtworks.xstream.XStream.<init>(XStream.java:514)
    com.thoughtworks.xstream.XStream.<init>(XStream.java:483)
    com.thoughtworks.xstream.XStream.<init>(XStream.java:429)
    com.thoughtworks.xstream.XStream.<init>(XStream.java:368)
    br.com.mmb.gerenciador.servlet.EmpresasService.service(EmpresasService.java:36)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
Note The full stack trace of the root cause is available in the server logs.

Apache Tomcat/9.0.56