Wednesday, November 14, 2012

Implementing an ExtJS Combobox in Apex (pt. 2/2)

This is the sequel from my previous blogpost. Now the static local data store of the ExtJS combobox will  be replaced with a remote data store.

To succeed the communications in JSON-format, i will use PL/JSON  by Jonas Krogsboell. It's a great utility, which provides the creating and parsing of json objects in pl/sql. If you shouldn't be experienced with this utility yet, here is an example script for introduction:

 tabResultset    json_list;
 tabParameters   json;
 tabResultset := json_dyn.executeList('select * from hr.employees where rownum < 5');

 tabParameters := json();
 tabParameters.put('Root', tabResultset);

This code dumps a json-object with records from the table "hr.employees" to the dbms-output-console. You can see how easily this can be accomplished. This code is also already the basis for the following data proxy package.

The intention is to create a universal procedure, where we pass the sql query as parameter and the json object including the recordset will be created. The json object should contain only those records from the current page and  the total row count of the query as additional information ("displaying records 25 - 49 of 128").

create or replace package pkg_data_proxy AS

   procedure pQueryJson(pSql varchar2, pStart pls_integer default null, pLimit pls_integer default null, pOutput varchar2 default 'htp');
end pkg_data_proxy;

create or replace
package body pkg_data_proxy AS

procedure pQueryJson(pSql varchar2, pStart pls_integer default null, pLimit pls_integer default null, pOutput varchar2 default 'htp') is

   tabResultset    adm.json_list;
   tabParameters   adm.json;

   vSqlEnvelope   varchar2(2000) := q'^
                          select * from 
                          (  select a.*, rownum as sql_rownum from 
                             ( select q.*, count(*) over () sql_totalrows  from 
                                (  #QUERY#
                                ) q
                             ) a where rownum <= #LIMIT#
                          ) where sql_rownum > #START#

   vTotalRows      pls_integer;


   wwv_flow_utilities.fast_replace(vSqlEnvelope, '#QUERY#', pSql);
   wwv_flow_utilities.fast_replace(vSqlEnvelope, '#START#', coalesce(to_char(pStart), '0'));
   wwv_flow_utilities.fast_replace(vSqlEnvelope, '#LIMIT#', coalesce(to_char(pStart + pLimit), 'rownum'));

   tabResultset := adm.json_dyn.executeList(vSqlEnvelope);
   tabParameters := adm.json();

   tabParameters.put('total', 0);
   tabParameters.put('rowset', tabResultset);

   vTotalRows := adm.json_ext.get_number(tabParameters, 'rowset[1].SQL_TOTALROWS');
   tabParameters.put('total', vTotalRows);

   if (pOutput = 'screen') then   
   end if;
end pQueryJson;

end pkg_data_proxy;

The parameters of the procedure "pQueryJson" are the sql query ("pSql"), the starting point of row count ("pStart"), the number of records ("pLimit") and the option to print the json object for debugging purposes to the dbms-output-console ("pOutput").
The query resultset is marked with "rowset" (line 38)  and the total row count of the query is copied into the header of the json object (line 40-41).

The complete json string for one record should look like this:

{"total":1,"rowset":[{"NAME":"David Austin","EMPLOYEE_ID":105,"PHONE_NUMBER":"590.423.4569","SALARY":4800,"SQL_TOTALROWS":1,"SQL_ROWNUM":1}]}

This procedure will be invoked in every ajax-call of the combobox, here is the updated code for the package "pkg_plugin_ext_combobox" including the new function "fAjax":

create or replace
PACKAGE pkg_plugin_ext_combobox AS

subtype typeAttr is apex_application_page_items.attribute_01%type;

function fRender (p_item                in apex_plugin.t_page_item,
                  p_plugin              in apex_plugin.t_plugin,
                  p_value               in varchar2,
                  p_is_readonly         in boolean,
                  p_is_printer_friendly in boolean) return apex_plugin.t_page_item_render_result;

function fAjax (p_item in apex_plugin.t_page_item, 
                p_plugin in apex_plugin.t_plugin ) return apex_plugin.t_page_item_ajax_result;

end pkg_plugin_ext_combobox;

create or replace
PACKAGE BODY pkg_plugin_ext_combobox AS

-- Private declarations

function fJsonProxy (p_item in apex_plugin.t_page_item, 
                     p_plugin in apex_plugin.t_plugin, 
                     p_value in varchar2 )
             return sys.dbms_sql.desc_tab2;

-- End private declarations

function fRender
    (p_item in apex_plugin.t_page_item, p_plugin in apex_plugin.t_plugin, p_value in varchar2,
     p_is_readonly in boolean, p_is_printer_friendly in boolean) 
  return apex_plugin.t_page_item_render_result is

   pDisplayColumn typeAttr := p_item.attribute_01;
   pValueColumn   typeAttr := p_item.attribute_02;
   pItemWidth     typeAttr := p_item.attribute_03;
   pEmptyText     typeAttr := p_item.attribute_05;
   pXTemplate     typeAttr := p_item.attribute_06;

   vResult        apex_plugin.t_page_item_render_result;  

   vItemValue     varchar2(32767) := sys.htf.escape_sc(p_value);
   vItemName      varchar2(200);
   vJsCode        varchar2(32767);
   vColumns       sys.dbms_sql.desc_tab2;


   if (apex_application.g_debug) then
      apex_plugin_util.debug_page_item (p_plugin => p_plugin, p_page_item => p_item, p_value => p_value,
            p_is_readonly => p_is_readonly, p_is_printer_friendly => p_is_printer_friendly );
   end if;

   vItemName := apex_plugin.get_input_name_for_page_item(false);

   vColumns := fJsonProxy(p_item => p_item, p_plugin => p_plugin, p_value => p_value );


   vJsCode := q'^
      {  var vCombo_#ITEM_ID# = Ext.create('Ext.form.field.ComboBox',
         {   transform: '#ITEM_ID#',
             store: vStore_#ITEM_ID#,
             queryMode: 'remote',
             queryParam: 'p_widget_num_return',
             displayField: '#DISPLAY_COLUMN#',
             valueField: '#VALUE_COLUMN#',
             hiddenName: '#ITEM_NAME#',
             emptyText: '#EMPTY_TEXT#',
             selectOnFocus: true,
             minChars: 1,
             {  resizable: true,
                resizeHandles: 'all',
                maxHeight: 400,
                maxWidth: 800
             width: #WIDTH#,
             pageSize: 1
         {  params : {  'x01' : '#VALUE#'},
            callback: function(records, operation, successful)
            { if (successful) 
              { vCombo_#ITEM_ID#.setValue(records[0]); 
              { vCombo_#ITEM_ID#.setValue("#EMPTY_TEXT#");


   wwv_flow_utilities.fast_replace(vJsCode, '#ITEM_ID#',;
   wwv_flow_utilities.fast_replace(vJsCode, '#ITEM_NAME#', vItemName);
   wwv_flow_utilities.fast_replace(vJsCode, '#VALUE#', vItemValue);
   wwv_flow_utilities.fast_replace(vJsCode, '#DISPLAY_COLUMN#', pDisplayColumn);
   wwv_flow_utilities.fast_replace(vJsCode, '#VALUE_COLUMN#', pValueColumn);
   wwv_flow_utilities.fast_replace(vJsCode, '#EMPTY_TEXT#', pEmptyText);
   wwv_flow_utilities.fast_replace(vJsCode, '#WIDTH#', pItemWidth);
   wwv_flow_utilities.fast_replace(vJsCode, '#XTEMPLATE#', pXTemplate);

   apex_javascript.add_onload_code(p_code => vJsCode);
   vResult.is_navigable := true;
   return (vResult);

end fRender;

function fAjax (p_item apex_plugin.t_page_item, p_plugin apex_plugin.t_plugin ) 
    return apex_plugin.t_page_item_ajax_result is

   pValueColumn   typeAttr := p_item.attribute_02;

   vSqlHandler  apex_plugin_util.t_sql_handler;
   vResult      apex_plugin.t_page_item_ajax_result;
   vSql         varchar2(32767);
   vBinds       dbms_sql.varchar2_table;


   vSql := p_item.lov_definition;

   vBinds := wwv_flow_utilities.get_binds(vSql);
   for i in 1..vBinds.count loop
      vSql := replace(lower(vSql), lower(vBinds(i)), '''' || v(ltrim(vBinds(i),':')) || '''');
   end loop;

   if (apex_application.g_widget_num_return is not null) then
      vSql := replace(vSql, '%%%', '%' || lower(apex_application.g_widget_num_return) || '%');
   end if;

   if (apex_application.g_x01 is not null) then
      vSql := vSql || ' and ' || pValueColumn || ' = ' || apex_application.g_x01;
   end if;

   pkg_data_proxy.pQueryJson(vSql, coalesce(apex_application.g_widget_action_mod, 0), coalesce(apex_application.g_widget_action, 100));


   return vResult;

   when others then

end fAjax;

function fJsonProxy (p_item in apex_plugin.t_page_item, p_plugin in apex_plugin.t_plugin, p_value in varchar2)
            return sys.dbms_sql.desc_tab2 is

   vSqlHandler     apex_plugin_util.t_sql_handler;
   vColCount       number;
   vColNames       varchar2(2000);
   vAjaxIdentifier varchar2(100);
   vPageSize       typeAttr  := p_item.attribute_04;

   vSqlHandler := apex_plugin_util.get_sql_handler (p_sql_statement => p_item.lov_definition,
                             p_min_columns => 1, p_max_columns => 999, p_component_name =>;
   vColCount := vSqlHandler.column_list.count();

   for i in 1 .. vColCount loop
      vColNames := vColNames || case when i > 1 then ',' end || '"' || upper(vSqlHandler.column_list(i).col_name) || '"';
   end loop;


   vAjaxIdentifier := apex_plugin.get_ajax_identifier;


   return vSqlHandler.column_list;

   when others then

end fJsonProxy;

end pkg_plugin_ext_combobox;

The local data store from the former "fRender"-function was removed. Instead of that, a new function "fJsonProxy" is called, which creates the remote data store.
At first this function gets the column names from our sql query and creates the data model. The data store sets an proxy to the database procedure "" to trigger the apex ajax calls. It's a bit fussy to get the correct mappings in the proxy attributes, but (as always) the webkit developer tools / firebug are the irreplaceable assistents when debugging ajax calls. In case of error, Apex itself keeps quiet and just throws a "404 page not found" due to security guidance.

The proxy properties in detail:
  • startParam: the starting point for the records rowcount, used for pagination, corresponds to "p_widget_action_mod" in Apex
  • limitParam: the number of records per page, corresponds to "p_widget_action"
  • pageParam: the starting page number, unset
  • noCache: set to "false", caching has to be enabled. Otherwise ExtJS would add a random "_dc"-Parameter to the URL like "". But Apex can't interpret/ignore this and fails. 
  • extraParams: Apex needs some more information like the app and page no. These are extracted from DOM and included in the "extraParams" section.
The create-command of the combobox in "fRender" stays almost the same, but some attributes are noteable. The attribut "pageSize" is no longer the number of records displayed per page. Now it just controls if the pagination toolbar should be displayed (yes/no)! The attribut "queryParam" contains the ongoing userinput of the item (for autocomplete) and is mapped to "p_widget_num_return".

You should also pay attention to the "hiddenName"-attribute. This creates a hidden input item with the value of the "valueField". Otherwise the value of the "displayField" would be submitted to database. ExtJs distinguishes between the value of an ExtJS-component and the corresponding DOM-element. By way of example,  the getValue()-method in "Ext.getCmp" differs elementary from the one in "Ext.get".
In consequence, we have to load the value of the "displayField" also via ajax call and set this value in the ExtJS-combobox (this happens in lines 84-94). Otherwise the employee id would be displayed, when loading a record during page refresh. This solution applies to version 4.1 of ExtJS -  in former releases it was quite easier, just by setting the "value"- and "valueField"-attributs in the combobox-config. Anyway, the primary key id for this ajax call is passed by using the apex parameter "x01". If this parameter is set, a  further condition will be added in the where-clause of the ajax call. It contains the filtering on the basis of the primary key, so that only one record with required the "DisplayName" is returned (line 141-143).

In order that, we hit the new function "fAjax". The call of the function has to be included in the apex item plugin: add "pkg_plugin_ext_combobox.fAjax" in the "AJAX function name" of the callbacks.

In function "fAjax" the sql query for the ajax call is getting prepared. At first it binds the page item variables (line 132 - 135). For example the apex page contains a field with the department id and the query should be filtered including the selected department. The comboxbox sql would contain a bind variable like :Px_DEPARTMENT_ID, which will be simply replaced with the actual value here.

Furthermore the functions checks, if the variable "apex_application.g_widget_num_return" is set. It contains the ongoing userinput of the item. The user enters "david" and all employees containing "david" will be automatically displayed (autocompletion). To understand the "replace"-command in line 138, please insert the following sql in the "list of values definition" of your apex item:

select first_name || ' ' || last_name as name,
from   hr.employees
where  lower(first_name || ' ' || last_name) like '%%%'

The "%%%"-Symbols are the placeholder for the search string the user has entered. They keep the query valid and the condition is always true (except when null, but this is not relevant), when no search text is entered. Of course this mechanism is quite rudimentary, but can be easily extended to the search criterias the developer needs.

At last, the purpose of checking the variable "apex_application.g_x01" was already explained before.

After all you should have this nice enhanced selectlist avaible now - and a good foundation to discover the enormous potential of the ExtJS-Framework furthermore.

The result of this blogposting

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