Tapestry Grid & Hibernate Criteria

Tapestry Grid is a very powerful tool for displaying a list of entities. It expects a GridDataSource as source parameter. A useful tool can be a TypeCoercer which converts a Criteria to GridDataSource.

Here is a simple implementation

public class Criteria2GridDataSourceCoercion implements Coercion<Criteria, GridDataSource> {

    public GridDataSource coerce(final Criteria criteria) {
        return new GridDataSource() {
            private List<?> cache;

            private int startIndex;

            public int getAvailableRows() {
                setupCriteria(Projections.rowCount(), 0, 1);
                long count = ((Long) criteria.uniqueResult());
                return (int) count;

            public void prepare(int startIndex, int endIndex, List<SortConstraint> sortConstraints) {
                setupCriteria(null, startIndex, endIndex - startIndex + 1);

                if (sortConstraints.size() != 0) {
                    for (SortConstraint sortConstraint : sortConstraints) {
                        String propertyName = sortConstraint.getPropertyModel().getPropertyName();
                                sortConstraint.getColumnSort() == ColumnSort.ASCENDING ?
                                        Order.asc(propertyName) : Order.desc(propertyName));

                cache = criteria.list();
                this.startIndex = startIndex;

            public Object getRowValue (int index) {
                return cache.get(index - startIndex);

            public Class getRowType() {
                if (cache == null) {
                    setupCriteria(null, 0, 1);
                    cache = criteria.list();

                if (cache.size() != 0) {
                    return cache.get(0).getClass();

                return null;

            private void setupCriteria(Projection projection, int firstResult, int maxResults) {

and in you Module class

    public static void addCoercion(Configuration<CoercionTuple> types) {
        types.add(new CoercionTuple(Criteria.class, GridDataSource.class,
                new Criteria2GridDataSourceCoercion()));


public class SamplePage {

    private Session session;

    public Criteria getCriteria() {
        Criteria criteria = session.createCriteria(MyEntity.class);
        return criteria;

<html xmlns:t='http://tapestry.apache.org/schema/tapestry_5_3.xsd'>
   <div t:type='Grid' t:source='criteria'>

Dragan came up with another useful Coercer to convert Criteria to Long

    public static void contributeTypeCoercer(Configuration configuration) {
        configuration.add(CoercionTuple.create(Criteria.class, Long.class,
                new Coercion() {
                    public Long coerce(Criteria input) {
                        input = input.setProjection(Projections.rowCount());
                        input = input.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY);
                        return (Long) input.uniqueResult();

        configuration.add(CoercionTuple.create(Criteria.class, List.class,
                new Coercion() {
                    public List coerce(Criteria input) {
                        return input.list();

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4 thoughts on “Tapestry Grid & Hibernate Criteria

  1. dragansah May 22, 2012 at 4:29 PM Reply

    This is almost the exact implementation as I have used in my projects. Good work !
    One thing though. If the criteria has no rows in the result – than you would have to know the class of the root entity, which you don’t in the example. One hack is to cast Criteria to CriteriaImpl (which is what is used for root criterias) and use criteria.getEntityOrClassName().

    I also have coercions to Long (for row count using projection not the expensive criteria.size()) and List


    • tawus May 22, 2012 at 4:56 PM Reply

      Hi Dragan

      Great! Why not blog it 🙂 and add a link or just add your code in a comment. It will help readers.

      • tawus May 22, 2012 at 6:48 PM

        Thanks Dragan, I have added your comment(code) to the bottom of the post

  2. Tapestry5 Grid component | kosmology June 25, 2012 at 5:50 PM Reply

    […] Tapestry5 Grid component […]

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