Wicket - Datatable custom pagination

Question

I am working on wicket datatable which uses built-in pagination feature where data is given through dataprovider. Wicket NavigationToolbar for displays links used to navigate the pages of the datatable as shown below

public class AbstractDataTable<T, S> extends DataTable<T, S> {
    private static final long serialVersionUID = -3370089530205846951L;

    public AbstractDataTable(String id, List<? extends IColumn<T, S>> columns, ISortableDataProvider<T, S> dataProvider) {
        this(id, columns, dataProvider, DataTableConstants.DEFAULT_ELEMS_PER_PAGE);
    }

    public AbstractDataTable(String id, List<? extends IColumn<T, S>> columns, ISortableDataProvider<T, S> dataProvider,
            int elemsPerPage) {
        super(id, columns, dataProvider, elemsPerPage);      
        addToolbars(dataProvider);
    }
    
    protected void addToolbars(ISortableDataProvider<T, S> dataProvider) {
        addTopToolbar(new HeadersToolbar<S>(this, dataProvider));
        addBottomToolbar(new NavigationToolbar(this));
        addBottomToolbar(new NoRecordsToolbar(this));
    }   

Here dataprovider holds entire data to be displayed so it takes too long time get entire data from database. So, to avoid that i am planning to implement pagination in such a way that to call database every time on clicking next button according to pagesize. Basically like below

select * from table_name LIMIT 25 OFFSET ${req.query.pageNumber25} will limit the number of records to 25. when req.query.pageNumber=1, it will offset first 25records and sends next 25 records. similarly if req.query.pageNumber=2, it will offset first 225 records and sends 51-75 records.

Got stuck here where i am looking ways to implement above feature

Update

Skeleton of dataprovider

public class DataTableProvider<T extends AbstractDataProvider> extends  BaseProvider implements Serializable {

    private static final long serialVersionUID = -6593326956377071200L;

    private final List<T> searchResults;

    public DataTableProvider() {
        this(null);
    }

    public DataTableProvider(List<T> bo) {
        this.searchResults = null != bo ? bo : new LinkedList<T>();
    }

    public List<T> provide() {
        return searchResults;
    }

    public int size() {
        return provide().size();
    }

    public void update(List<T> bos) {
        searchResults.clear();
        searchResults.addAll(null != bos ? bos : Collections.<T> emptyList());
    }

    public boolean isEmpty() {
        return provide().isEmpty();
    }
}

Above dataprovider is populate on clicking the search button

    @Override
    protected void onSubmit(SearchFilterBO criteria) {
        if (getLog().isDebugEnabled()) {
            getLog().debug(format(MSG_PTRN_SEARCH_SUBMISSION, ToStringBuilder.reflectionToString(criteria)));
        }
        getResultsProvider().update(searchService.searchBy(criteria));
        getLog().info(format(MSG_PTRN_SEARCH_ENDED, getResultsProvider().size()));
    }

Answer 1

Your implementation of data provider is incorrect. You have to override 'iterator' method of IDataProvider and select your data there. Also BaseProvider is not presented in wicket libs. Here is a simple example:

IDataProvider<Location> provider = new IDataProvider<>() {
        @Override
        public Iterator<? extends Location> iterator(long first, long count) { 
            return getLocationDAO().findAll(first, count).iterator();
        }

        @Override
        public long size() {
            return getLocationDAO().getTotal();
        }

        @Override
        public IModel<Location> model(Location object) {
            return new Model<>(object);
        }
    };