json - Return Object Null datasnap delphi XE2 and consuming in java Android -

when not want return object , return nil on server, proxy classes generated exception not convert on tjsonnull tjsonobject .. normal? can return null or tjsonnulll?

function tservermethods.getpais(codigo: integer; var erro:string): tpais; var   qry: tzquery; begin   result := nil;   try     qry := createqueryconectado(erro);     qry     begin       close;       sql.clear;       sql.add(sql_get_listpaises);       sql.add(' pais_codigo = :p00 ');       parambyname('p00').asinteger := codigo;       open;       if not isempty       begin         result := createpais;         result.codigo := fieldbyname('pais_codigo').asinteger;         result.nome := fieldbyname('pais_descricao').asstring;         result.lingua := fieldbyname('pais_lingua').asstring;         result.moeda := fieldbyname('pais_moeda').asstring;         result.taxacambio := fieldbyname('pais_taxacambio').ascurrency;         result.locale := fieldbyname('pais_locale').asstring;       end;     end;   except     on e: exception     begin       erro := tratarexception(e);     end;   end; end; 

for example query customer not exist.

this error in proxy classes

    java.lang.classcastexception: com.embarcadero.javaandroid.tjsonnull cannot cast com.embarcadero.javaandroid.tjsonobject 08-15 11:55:03.759: w/system.err(28204):  @ com.embarcadero.javaandroid.dsproxy$tservermethods.getpais(dsproxy.java:1773) 

is proxy

private dsrestparametermetadata[] tservermethods_getpais_metadata; private dsrestparametermetadata[] get_tservermethods_getpais_metadata() {   if (tservermethods_getpais_metadata == null) {     tservermethods_getpais_metadata = new dsrestparametermetadata[]{       new dsrestparametermetadata("codigo", dsrestparamdirection.input, dbxdatatypes.int32type, "integer"),       new dsrestparametermetadata("erro", dsrestparamdirection.inputoutput, dbxdatatypes.widestringtype, "string"),       new dsrestparametermetadata("", dsrestparamdirection.returnvalue, dbxdatatypes.jsonvaluetype, "tpais"),     };   }   return tservermethods_getpais_metadata; }  /**  * @param codigo [in] - type on server: integer  * @param erro [in/out] - type on server: string  * @return result - type on server: tpais  */ public static class getpaisreturns {   public string erro;   public tjsonobject returnvalue; } public getpaisreturns getpais(int codigo, string erro) throws dbxexception {   dsrestcommand cmd = getconnection().createcommand();   cmd.setrequesttype(dshttprequesttype.get);   cmd.settext("tservermethods.getpais");   cmd.prepare(get_tservermethods_getpais_metadata());   cmd.getparameter(0).getvalue().setasint32(codigo);   cmd.getparameter(1).getvalue().setasstring(erro);   getconnection().execute(cmd);   getpaisreturns ret = new getpaisreturns();   ret.erro = cmd.getparameter(1).getvalue().getasstring();   ret.returnvalue = (tjsonobject)cmd.getparameter(2).getvalue().getasjsonvalue();   return ret; } 

tanks!