java - dropdown select as ID and pass to action class but in search query i have given if null then search all content . how can i search by dropdown ID? -

    function searchcontentdisplay(key)     {        var paramtypeid=$("#paramlist").val();        var paramvalue = document.getelementbyid("paramval").value;         alert(paramvalue+paramtypeid);         $("#ajax_loader").show('slow');         $.ajax({             url : "serachglobalparam",             type : "post",             data : 'globalparamdto.paramtypeid='+paramtypeid+'&globalparamdto.paramvalue='+paramvalue,             async : true,             cache : false,             mimetype:"multipart/form-data",              beforesend: function(){                  $("#ajax_loader").show('slow');                 },              complete: function(){                     $("#ajax_loader").hide('slow');                 },             success : function (data) {             $("#searchglobalparam").html(data);              }             });         } 

i want search content on select dropdown , id pass ajax. if dont select value dropdown search content list .the query working fine when on mysql have taken null select empty dropdown , serach content when pass selected dropdown on ajax work id .if select nothing 0 pass on ajax , travel action class 0 in query have given if null serach content .it seems problem between null , 0.

i have set if paramtypeid == 0 paramtypeid= null null travel action class not execute while.next statement dont know why not working.try { pstmt = conn.preparestatement(slcmqueryconstant.search_global_param);

        pstmt.setstring(1,globalparamdto.getparamtypeid());         system.out.println(globalparamdto.getparamtypeid());         pstmt.setstring(2, globalparamdto.getparamvalue());         rs = pstmt.executequery();         while (rs.next()) {             globalparamdto globalparamdto= new globalparamdto();             globalparamdto.setparamvalue(rs.getstring("value"));             globalparamdto.setparamtypename(rs.getstring("param_type_name"));             paramlist.add(globalparamdto);         }     } catch (sqlexception e) {          e.printstacktrace();