code: void mapInField(Object from, String from_field, Object to, String to_in) {
          if (to == ca.getComponent()) {
              throw new ComponentException("wrong connect:" + from_field);
          }
          ComponentAccess ca_to = lookup(to);
          Access to_access = ca_to.input(to_in);
          checkFA(to_access, to, to_in);
          try {
              FieldContent.FA f = new FieldContent.FA(from, from_field);
              ca_to.setInput(to_in, new FieldObjectAccess(to_access, f, ens));
              if (log.isLoggable(Level.CONFIG)) {
                  log.config(String.format("Field(%s) -> @In(%s)", f.toString(), to_access.toString()));
              }
  
          } catch (Exception E) {
              throw new ComponentException("No such field '" + from.getClass().getCanonicalName() + "." + from_field + "'");
          }
      }
docs: Map an input field.
  
  @param from
  @param from_field
  @param to
  @param to_in