Vlaue List Handler using CachedRowSet

advantage : assume that the query results 1000 records. in this implementation at server side u cache a 100 records (page size) out of 1000and deliver these 100 and eventually all 1000 records to client in a frame requested by client (say 10 records per page)disadvantage : the com.sun.rowset.CachedRowSetImpl DOES NOT WORK SOMETIMES.i dont know ! i was not able to look into its impl as i guess its source is not available.below is the whole code!// stateful session bean interfacepackage session;// add imports@Remote()public interface CachedRowSetListerSessionRemoteextends CachedRowSetValueListIterator{public void executeStaffSearch(CriteriaVO oCriteriaVO,RequiredFieldsVO oRequiredFieldsVO) throws ListHandlerException;}// stateful session bean implpackage session;// add imports@Stateful(mappedName = "CachedListerSessionBean")public class CachedRowSetListerSessionBeanextends CachedRowSetValueListHandlerimplements CachedRowSetListerSessionRemote{public void executeStaffSearch(CriteriaVO oCriteriaVO,RequiredFieldsVO oRequiredFieldsVO) throws ListHandlerException{// Create DAO instance and fetch the list// according to the required FieldsStaffDAO oStaffDAO = DAOFactory.getDAOFactory(DAOFactory.POSTGRES).getStaffDAO();// Set the total size of the listint iSize = oStaffDAO.getListSize();setSize(iSize);// get the list from dao and set it// this list is nothing but custom list impl// (iterating over list is simple compared to that of cachedrowset cursor !)// get the required level of dataswitch(oRequiredFieldsVO.getListingLevel()){// if L1 : minimum data (from a same table all compulsary columns)case L1:setList(new RowSetWrapperList(oStaffDAO.getL1Detail(oCriteriaVO),iSize));break;// if L2 : medium data (from a same table all columns)case L2:setList(new RowSetWrapperList(oStaffDAO.getL2Detail(oCriteriaVO),iSize));break;// if L2 : maximum data (from a same table as well as related relational tables data)case L3:setList(new RowSetWrapperList(oStaffDAO.getL3Detail(oCriteriaVO),iSize));break;}setList(new RowSetWrapperList(oStaffDAO.getList(oCriteriaVO),iSize));}}}// value list handler classpackage session;// add importspublic abstract class CachedRowSetValueListHandlerimplements ValueListIterator{private List moList;private ListIterator moListIterator;private int miListSize;public CachedRowSetValueListHandler(){moLogger.debug("Called the constructor");}protected void setSize(int lSize){miListSize = lSize;}public int getSize(){moLogger.debug("Get the size in the getSize method: " + miListSize);return miListSize;}public List getNextElements(int iSize) throws IteratorException{int iCount = 0;Object oObject = null;ArrayList oList = new ArrayList();if(moListIterator != null){while(moListIterator.hasNext() && (iCount < oobject =" moListIterator.next();oList.add(oObject);iCount++;}}else{throw" icount =" 0;Object" oobject =" null;ArrayList" olist =" new" oobject =" moListIterator.previous();oList.add(oObject);iCount++;}}else{throw" olist =" new">= 0 && iStartIndex < icounter =" iStartIndex" molistiterator =" moList.listIterator();}}protected" molist =" oList;moLogger.debug(" molistiterator =" moList.listIterator();}}//" mologger =" Logger.getLogger(RowSetWrapperList.class.getName());private" mocachedrowset =" null;private" misize =" 0;public" micurrentpage =" 0;public" mimaxnoofpages =" 0;public" row_set_page_size =" 100;public" mocachedrowset =" oCachedRowSet;miSize" mimaxnoofpages =" miSize" mimaxnoofpages =" miSize" mimaxnoofpages =" miMaxNoOfPages" misize ="=""> miSize){moLogger.error("index " + iIndex + " out of bound !");throw new IndexOutOfBoundsException("index " + iIndex+ " out of bound !");}// find on which page this object isint iPage = 0;int iPageLocation = iIndex % ROW_SET_PAGE_SIZE;if(iPageLocation == 0){iPage = iIndex / ROW_SET_PAGE_SIZE;iPage--;iPageLocation = ROW_SET_PAGE_SIZE;}else{iPage = iIndex / ROW_SET_PAGE_SIZE;}moLogger.debug("the requested object is on page " + iPage);moLogger.debug("the requested object is at location "+ iPageLocation);// get the object// check whether object is on current pageif(micurrentPage == iPage){// object is on same page// get itmoCachedRowSet.absolute(iPageLocation);return createStaffTO();}// object is not on current page// go to that pageif(micurrentPage < ipagecounter =" 0;int" ihowmuchahead =" iPage" ipagecounter =" 0;int" ihowmuchbehind =" micurrentPage" breturn =" moCachedRowSet.nextPage();if(bReturn){moLogger.debug(" href="http://forum.java.sun.com/thread.jspa?threadID=769985" target="_blank">http://forum.java.sun.com/thread.jspa?threadID=769985if(!moCachedRowSet.nextPage()){moCachedRowSet.previousPage();}}private void goToPreviousPage() throws SQLException{boolean bReturn = moCachedRowSet.previousPage();if(bReturn){moLogger.debug("yup its previous page now");}else{moLogger.debug("this is the first page");}}public Object set(int iIndex, Object oElement){throw new UnsupportedOperationException("RowSetWrapperList does not support set operation");}public void add(int iIndex, Object oElement){throw new UnsupportedOperationException("RowSetWrapperList does not support add operation");}public Object remove(int iIndex){throw new UnsupportedOperationException("RowSetWrapperList does not support remove operation");}public int indexOf(Object oObject){throw new UnsupportedOperationException("RowSetWrapperList does not support indexOf operation");}public int lastIndexOf(Object oObject){throw new UnsupportedOperationException("RowSetWrapperList does not support lastIndexOf operation");}public ListIterator listIterator(){return new DataRowListIterator();}public ListIterator listIterator(int iIndex){throw new UnsupportedOperationException("RowSetWrapperList does not support listIterator operation");}public List subList(int iFromIndex, int iToIndex){throw new UnsupportedOperationException("RowSetWrapperList does not support subList operation");}private StaffTO createStaffTO(){StaffTO oStaffTO = null;moLogger.debug("inside Create Array List");try{oStaffTO = new StaffTO();oStaffTO.setStaffId(moCachedRowSet.getInt(1));moLogger.debug("inside Create Array List -- "+ oStaffTO.getStaffId());oStaffTO.setFirstName(moCachedRowSet.getString(2));moLogger.debug("inside Create Array List -- "+ oStaffTO.getFirstName());oStaffTO.setMiddleName(moCachedRowSet.getString(3));moLogger.debug("inside Create Array List -- "+ oStaffTO.getMiddleName());oStaffTO.setLastName(moCachedRowSet.getString(4));moLogger.debug("inside Create Array List -- "+ oStaffTO.getLastName());oStaffTO.setDesignation(StaffDesignation.values()[moCachedRowSet.getInt(5)]);moLogger.debug("inside Create Array List -- "+ oStaffTO.getDesignation());}catch(SQLException oSQLException){moLogger.error("Could not fetch data from resultset", oSQLException);throw new InternalException("Could not fetch data from resultset : "+ oSQLException.getMessage());}return oStaffTO;}private class DataRowListIteratorimplements ListIterator{private int miCurrentRow = 0;public void add(Object oObject){throw new UnsupportedOperationException("DataRowListIterator does not support add operation");}public boolean hasNext(){return miCurrentRow != size();}public boolean hasPrevious(){return miCurrentRow != 0;}public Object next(){return get(++miCurrentRow);}public int nextIndex(){return miCurrentRow;}public Object previous(){return get(miCurrentRow--);}public int previousIndex(){return miCurrentRow - 1;}public void remove(){throw new UnsupportedOperationException("DataRowListIterator does not support remove operation");}public void set(Object oObject){throw new UnsupportedOperationException("DataRowListIterator does not support set operation");}}}// staff daopackage dao;// add importspublic class StaffDAO{private static final Logger moLogger = Logger.getLogger(CourseDAO.class.getName());private final String ASCENDING = "asc";private final String DESCENDING = "desc";private static StaffDAO moStaffDAO = null;private StaffDAO(){// do nothing}public static synchronized StaffDAO getInstance(){if(moStaffDAO == null){moStaffDAO = new StaffDAO();}return moStaffDAO;}public CachedRowSet getL1Detail(CriteriaVO oCriteriaVO){String szSortCriteria = null;CachedRowSet oCachedRowSet = null;try{if(oCriteriaVO.isAscending()){szSortCriteria = ASCENDING;}else{szSortCriteria = DESCENDING;}oCachedRowSet = new CachedRowSetImpl();oCachedRowSet.setDataSourceName(PostgresDAOFactory.DATASOURCE);oCachedRowSet.setPageSize(RowSetWrapperList.ROW_SET_PAGE_SIZE);oCachedRowSet.setCommand("select staff_id, first_name, middle_name, last_name, designation from staff "+ " where is_deleted != '1' order by first_name "+ szSortCriteria);oCachedRowSet.execute();}catch(SQLException oSQLException){moLogger.error("cannot execute at level1", oSQLException);throw new InternalException("cannot execute at level1 : "+ oSQLException.getMessage());}return oCachedRowSet;}public int getListSize(){Connection oConnection = null;Statement oStatement = null;ResultSet oResultSet = null;try{oConnection = PostgresDAOFactory.createConnection();oStatement = oConnection.createStatement();oResultSet = oStatement.executeQuery("SELECT count(*) from staff WHERE is_deleted !='1'");oResultSet.next();int iCount = oResultSet.getInt(1);moLogger.debug("Result Set Size" + iCount);return iCount;}catch(SQLException oSQLException){moLogger.error("cannot execute at get Size", oSQLException);throw new InternalException("cannot execute at get Size -- "+ oSQLException.getMessage());}finally{try{if(oResultSet != null){oResultSet.close();}}catch(SQLException oSQLException){// ignore}try{if(oStatement != null){oStatement.close();}}catch(SQLException oSQLException){// ignore}try{if(oConnection != null){oConnection.close();}}catch(SQLException oSQLException){// ignore}}}}