code: public Properties getSystemProperties() throws Exception {
          final String[] address = { CORE_SERVICE, PLATFORM_MBEAN, "type", "runtime" };
          final ModelNode op = createReadAttributeRequest(true, "system-properties", Address.root().add(address));
          final ModelNode results = execute(op);
          if (isSuccess(results)) {
              // extract the DMR representation into a java Properties object
              final Properties sysprops = new Properties();
              final ModelNode node = getResults(results);
              final List<Property> propertyList = node.asPropertyList();
              for (Property property : propertyList) {
                  final String name = property.getName();
                  final ModelNode value = property.getValue();
                  if (name != null) {
                      sysprops.put(name, value != null ? value.asString() : "");
                  }
              }
              return sysprops;
          } else {
              throw new FailureException(results, "Failed to get system properties");
          }
      }
docs: This returns the system properties that are set in the AS JVM. This is not the system properties
  in the JVM of this client object - it is actually the system properties in the remote
  JVM of the AS instance that the client is talking to.
  
  @return the AS JVM's system properties
  @throws Exception any error