RichFaces ExtendedTableDataModel: sorting columns

Question

We use the ExtendedTableDataModel for paging. This is done to retrieve a set of results with Hibernate and load the next set when another page is requested.

All works fine, but if we sort columns by using rich:column sortBy within the rich:dataTable then RichFaces tries to load all rows. We can see this while debugging the getItemsByRange which we made for our custom DataProvider. After clicking sort once, RichFaces will continue to retrieve all rows from the database. This is of course not what we want. We wanted to use this solution to minimize the data traffic and load times.

We use Richfaces 3.3.2. Is there someone with a possible solution or workaround?

Answer 1

We had the same problem, and here's our solution. I'm not entirely sure that the whole code I'm pasting is relevant, but it should be

public class PagingExtendedTableDataModel<T> extends ExtendedDataModel implements
        Serializable, Modifiable {

    private DataProvider dataProvider;
    private Object rowKey;
    private List wrappedKeys;
    private Map wrappedData;
    private Integer rowCount;
    private Integer rowIndex;
    private List<FilterField> filterFields;
    private List<SortField2> sortFields;

    public PagingExtendedTableDataModel(DataProvider<T> dataProvider) {
        wrappedKeys = null;
        wrappedData = new HashMap();
        rowCount = null;
        rowIndex = Integer.valueOf(-1);
        rowKey = null;

        this.dataProvider = dataProvider;
    }

    public Object getRowKey() {
        return rowKey;
    }

    public void setRowKey(Object key) {
        rowKey = key;
    }

    @SuppressWarnings("unchecked")
    public void walk(FacesContext context, DataVisitor visitor, Range range,
            Object argument) throws IOException {

        int rowC = getRowCount();
        int firstRow = ((SequenceRange) range).getFirstRow();
        int numberOfRows = ((SequenceRange) range).getRows();
        if (numberOfRows <= 0) {
            numberOfRows = rowC;
        }

        if (wrappedKeys != null) {
            Object key;
            for (Iterator it = wrappedKeys.iterator(); it.hasNext();
                visitor.process(context, key, argument)) {

                key = it.next();
                setRowKey(key);
            }

        } else {
            wrappedKeys = new ArrayList();
            int endRow = firstRow + numberOfRows;
            if (endRow > rowC) {
                endRow = rowC;
            }

            if (dataProvider instanceof Sortable2) {
                ((Sortable2) dataProvider).setSortFields(sortFields);
            }

            if (dataProvider instanceof Filterable) {
                ((Filterable) dataProvider).setFilterFields(filterFields);
            }

            Object key;
            for (Iterator it = loadData(firstRow, endRow).iterator(); it.hasNext();
                visitor.process(context, key, argument)) {

                Object item = it.next();
                key = getKey(item);
                wrappedKeys.add(key);
                wrappedData.put(key, item);
            }

        }
    }

    protected List loadData(int startRow, int endRow) {
        if (startRow < 0) {
            startRow = 0;
            throw new IllegalArgumentException((new StringBuilder()).append(
                    "Illegal start index value: ").append(startRow).toString());
        }
        int rowCount = getRowCount();
        if (endRow > rowCount) {
            endRow = rowCount;
            throw new IllegalArgumentException((new StringBuilder()).append(
                    "Illegal end index value: ").append(endRow).toString());
        }

        return dataProvider.getItemsByRange(startRow, endRow);
    }

    public int getRowCount() {
        if (rowCount == null) {
            rowCount = new Integer(dataProvider.getRowCount());
        } else {
            return rowCount.intValue();
        }

        return rowCount.intValue();
    }

    public Object getRowData() {
        if (rowKey == null) {
            return null;
        }

        return getObjectByKey(rowKey);
    }

    @SuppressWarnings("unchecked")
    public Object getKey(Object o) {
        return dataProvider.getKey(o);
    }

    @SuppressWarnings("unchecked")
    public Object getObjectByKey(Object key) {
        Object t = wrappedData.get(key);
        if (t == null) {
            t = dataProvider.getItemByKey(key);
            wrappedData.put(key, t);
        }
        return t;
    }

    public int getRowIndex() {
        return rowIndex.intValue();
    }

    public void setRowIndex(int rowIndex) {
        this.rowIndex = Integer.valueOf(rowIndex);
    }

    public Object getWrappedData() {
        throw new UnsupportedOperationException();
    }

    public void setWrappedData(Object data) {
        throw new UnsupportedOperationException();
    }

    public boolean isRowAvailable() {
        return getRowData() != null;
    }

    public void reset() {
        wrappedKeys = null;
        wrappedData.clear();
        rowCount = null;
        rowIndex = Integer.valueOf(-1);
        rowKey = null;
    }

    public DataProvider getDataProvider() {
        return dataProvider;
    }

    public void setDataProvider(DataProvider dataProvider) {
        this.dataProvider = dataProvider;
    }

    @Override
    public void modify(List<FilterField> filterFields, List<SortField2> sortFields) {
        this.filterFields = filterFields;
        this.sortFields = sortFields;

        reset();
    }
}

And you also need a custom DataProvider

public class PagingDataProvider implements DataProvider<BeanDisplay>,
      Sortable2, Filterable 

In the method getItemsByRange make your query load only a limited amount of records. All other methods should be straightforward to implement (I'm not pasting our code, because it is full of quite specific code, which is not relevant)

And you construct your data model as follows:

new PagingExtendedTableDataModel<BeanDisplay>(new PagingDataProvider());