code: protected void exportFormPropertyToContext(RequestManager requestManager, WebContext context, ActionRuntime runtime) {
          runtime.getActionForm().ifPresent(virtualForm -> {
              final ActionFormMeta meta = virtualForm.getFormMeta();
              final Collection<ActionFormProperty> properties = meta.properties();
              if (properties.isEmpty()) {
                  return;
              }
              for (ActionFormProperty property : properties) {
                  if (isExportableProperty(property.getPropertyDesc())) {
                      final String propertyName = property.getPropertyName();
                      checkFormPropertyUsingReservedWord(runtime, virtualForm, propertyName);
                      checkFormPropertyConflictingWithRegisteredData(runtime, context, propertyName);
                      final Object propertyValue = virtualForm.getPropertyValue(property);
                      if (propertyValue != null) {
                          context.setVariable(propertyName, propertyValue);
                      }
                  }
              }
          });
      }
docs: ===========