Accumulative sorting in ADF 10g tables - backing

gistfile1.java

import oracle.adf.view.faces.event.SortEvent;
import oracle.adf.view.faces.model.SortCriterion;
import oracle.adf.view.faces.component.core.data.CoreTable;

import java.util.List;
import java.util.ArrayList;

public class Customers {

	public void onSort(SortEvent se) {
		// get selected criterion
		List sortList = se.getSortCriteria();
		SortCriterion currentSortCriterion = (SortCriterion)sortList.get(0);
		// get previously selected criteria
		ArrayList persistentSortList = getCustomerTableSortCriteria();
		// the rest of the code expands the sort criteria, applies the new criteria list to the table and saves the criteria list for the future
		ArrayList updatedSortList = new ArrayList();
		updatedSortList.add(0, currentSortCriterion);
		for(Object o : persistentSortList) {
			updatedSortList.add((SortCriterion)o);
		}
		CoreTable ct = (CoreTable)se.getComponent();
		ct.setSortCriteria(updatedSortList);
		setCustomerTableSortCriteria(updatedSortList);
	}

	public static final String CUSTOMER_TABLE_SORT_CRITERIA = "customerTableSortCriteria";

	/* As the sort criteria returned at any call to the onSort method have request scope,
	 * I use a session scoped bean that I call viewScope (I clean it up every time the viewId is changed, meaning that user has entered another page) which in fact is a java.util.HashMap.
	 * The method getCustomerTableSortCriteria() returns the Object under key CUSTOMER_TABLE_SORT_CRITERIA stored in viewScope.
	 * Naturally instead of viewScope one can use any other session scoped bean to store the ArrayList of SortCriterion objects.
	 */

	private ArrayList getCustomerTableSortCriteria() {
		ArrayList sortCriteria = (ArrayList)viewScope.get(CUSTOMER_TABLE_SORT_CRITERIA);
		if(sortCriteria == null) {
			sortCriteria = new ArrayList();
			setCustomerTableSortCriteria(sortCriteria);
		}
		return sortCriteria;
	}

	private void setCustomerTableSortCriteria(ArrayList sortCriteria) {
		viewScope.put(CUSTOMER_TABLE_SORT_CRITERIA, sortCriteria);
	}
}