How to do sorting/filtering on custom java data source implementation

Question

Hi,
I have an entity driven view object whose data should be retrieved and populated using custom java data source implementation. I've done the same as said in document. I understand that Query mode should be the default one (i.e. database tables) and createRowFromResultSet will be called as many times as it needs based on the no. of data retrieved from service, provided we should write the logic for hasNextForCollection(). Implementation sample code is given below.
protected void executeQueryForCollection(Object qc, Object[] params, int noUserParams) {      
Iterator datumItr = retrieveDataFromService(qc, params);
setUserDataForCollection(qc, datumItr);
hasNextForCollection(qc);
super.executeQueryForCollection(qc, params, noUserParams);
protected boolean hasNextForCollection(Object qc) {
Iterator datumItr = (Iterator) getUserDataForCollection(qc);
if (datumItr != null && datumItr.hasNext()){
return true;
setCallService(false);
setFetchCompleteForCollection(qc, true);
return false;
protected ViewRowImpl createRowFromResultSet(Object qc, ResultSet resultSet) {
Iterator datumItr = (Iterator) getUserDataForCollection(qc);
Object datumObj = datumItr.next();
ViewRowImpl r = createNewRowForCollection(qc);
return r;
Everything is working fine include table sorting/filtering. Then i noticed that everytime when user perform sorting/filtering, executeQueryForCollection is called, which in turn calls my service. It is a performance issue. I want to avoid. So i did some modification in the implementation in such a way that, service call will happen only if the callService flag is set to true, followed by executeQuery(). Code is given below.
private boolean callService = false;
public void setCallService(boolean callService){
this.callService = callService;
public boolean isCallService(){
return callService;
protected void executeQueryForCollection(Object qc, Object[] params, int noUserParams){
if (callService)
Iterator datumItr = retrieveDataFromService(qc, params);
setUserDataForCollection(qc, datumItr);
hasNextForCollection(qc);
super.executeQueryForCollection(qc, params, noUserParams);
Issue i have:
When user attempts to use table sort/filter, since i skipped the service call and set null as userDataCollection, createRowFromResultSet is not called and data which i retrieved and populated to view object is totally got vanished!!. I've already retrived data and created row from result set. Why it should get vanished? Don't know why.
Tried solution:
I came to know that query mode should be set to Scan_Entity_Cache for filtering and Scan_View_Rows for sorting. I din't disturb the implementation (i.e. skipping service call) but overrided the executeQuery and did like the following code.
@Override
public void executeQuery(){
setQueryMode(callService ? ViewObject.QUERY_MODE_SCAN_DATABASE_TABLES : ViewObject.QUERY_MODE_SCAN_ENTITY_ROWS);
super.executeQuery();
By doing this, i could able to do table filtering but when i try to use table sorting or programmatic sorting, sorting is not at all applied.
I changed the code like beolw*
@Override
public void executeQuery(){
setQueryMode(callService ? ViewObject.QUERY_MODE_SCAN_DATABASE_TABLES : ViewObject.QUERY_MODE_SCAN_VIEW_ROWS);
super.executeQuery();
Now sorting is working fine but filtering is not working in an expected way because Scan_View_rows will do further filtering of view rows.
Question:
I don't know how to achieve both filtering and sorting as well as skipping of service call too.
Can anyone help on this?? Thanks in advance.
Raguraman

Answer 1

Hi,
I have an entity driven view object whose data should be retrieved and populated using custom java data source implementation. I've done the same as said in document. I understand that Query mode should be the default one (i.e. database tables) and createRowFromResultSet will be called as many times as it needs based on the no. of data retrieved from service, provided we should write the logic for hasNextForCollection(). Implementation sample code is given below.
protected void executeQueryForCollection(Object qc, Object[] params, int noUserParams) {
  Iterator datumItr = retrieveDataFromService(qc, params);
  setUserDataForCollection(qc, datumItr);
  hasNextForCollection(qc);
  super.executeQueryForCollection(qc, params, noUserParams);
protected boolean hasNextForCollection(Object qc) {
  Iterator datumItr = (Iterator) getUserDataForCollection(qc);
  if (datumItr != null && datumItr.hasNext()){
    return true;
  setFetchCompleteForCollection(qc, true);
  return false;
protected ViewRowImpl createRowFromResultSet(Object qc, ResultSet resultSet) {
  Iterator datumItr = (Iterator) getUserDataForCollection(qc);
  Object datumObj = datumItr.next();
  ViewRowImpl r = createNewRowForCollection(qc);
  return r;
}Everything is working fine include table sorting/filtering. Then i noticed that everytime when user perform sorting/filtering, executeQueryForCollection is called, which in turn calls my service. It is a performance issue. I want to avoid. So i did some modification in the implementation in such a way that, service call will happen only if the callService flag is set to true, followed by executeQuery(). Code is given below.
private boolean callService = false;
public void setCallService(boolean callService){
  this.callService = callService;
public boolean isCallService(){
  return callService;
protected void executeQueryForCollection(Object qc, Object[] params, int noUserParams){
  if (callService) {
    Iterator datumItr = retrieveDataFromService(qc, params);
    setUserDataForCollection(qc, datumItr);
  hasNextForCollection(qc);
  super.executeQueryForCollection(qc, params, noUserParams);
}Issue i have:
When user attempts to use table sort/filter, since i skipped the service call and storing of userDataCollection, createRowFromResultSet is not called and data which i retrieved and populated to view object is totally got vanished!!. I've already retrived data and created row from result set. Why it should get vanished? Don't know why.
Tried solution:
I came to know that query mode should be set to Scan_Entity_Cache for filtering and Scan_View_Rows for sorting. I din't disturb the implementation (i.e. skipping service call) but overrided the executeQuery and did like the following code.
@Override
public void executeQuery(){
  setQueryMode(callService ? ViewObject.QUERY_MODE_SCAN_DATABASE_TABLES : ViewObject.QUERY_MODE_SCAN_ENTITY_ROWS);
  super.executeQuery();
}By doing this, i could able to do table filtering but when i try to use table sorting or programmatic sorting, sorting is not at all getting applied.
I changed the code like below one (i.e. changed to ViewObject.QUERY_MODE_SCAN_VIEW_ROWS instead of ViewObject.QUERY_MODE_SCAN_ENTITY_ROWS)
@Override
public void executeQuery(){
  setQueryMode(callService ? ViewObject.QUERY_MODE_SCAN_DATABASE_TABLES : ViewObject.QUERY_MODE_SCAN_VIEW_ROWS);
  super.executeQuery();
}Now sorting is working fine but filtering is not working in an expected way because Scan_View_rows will do further filtering of view rows.
If i OR'ed the Query Mode as given below, i am getting duplicate rows. (vewObject.QUERY_MODE_SCAN_ENTITY_ROWS | ViewObject.QUERY_MODE_SCAN_VIEW_ROWS) Question:
I don't know how to achieve both filtering and sorting as well as skipping of service call too.
Can anyone help on this?? Thanks in advance.
Raguraman
Edited by: Raguraman on Apr 12, 2011 6:53 AM