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> {
@Override
public GridDataSource coerce(final Criteria criteria) {
return new GridDataSource() {
private List<?> cache;
private int startIndex;
@Override
public int getAvailableRows() {
setupCriteria(Projections.rowCount(), 0, 1);
long count = ((Long) criteria.uniqueResult());
return (int) count;
}
@Override
public void prepare(int startIndex, int endIndex, List<SortConstraint> sortConstraints) {
setupCriteria(null, startIndex, endIndex - startIndex + 1);
criteria.setResultTransformer(Criteria.ROOT_ENTITY);
if (sortConstraints.size() != 0) {
for (SortConstraint sortConstraint : sortConstraints) {
String propertyName = sortConstraint.getPropertyModel().getPropertyName();
criteria.addOrder(
sortConstraint.getColumnSort() == ColumnSort.ASCENDING ?
Order.asc(propertyName) : Order.desc(propertyName));
}
}
cache = criteria.list();
this.startIndex = startIndex;
}
@Override
public Object getRowValue (int index) {
return cache.get(index - startIndex);
}
@Override
public Class getRowType() {
if (cache == null) {
setupCriteria(null, 0, 1);
criteria.setResultTransformer(Criteria.ROOT_ENTITY);
cache = criteria.list();
}
if (cache.size() != 0) {
return cache.get(0).getClass();
}
return null;
}
private void setupCriteria(Projection projection, int firstResult, int maxResults) {
criteria.setProjection(projection).setFirstResult(firstResult).setMaxResults
(maxResults);
}
};
}
}
and in you Module class
@Contribute(TypeCoercer.class)
public static void addCoercion(Configuration<CoercionTuple> types) {
types.add(new CoercionTuple(Criteria.class, GridDataSource.class,
new Criteria2GridDataSourceCoercion()));
}
Usage
public class SamplePage {
@Inject
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'> </div> </html>
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() {
@Override
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() {
@Override
public List coerce(Criteria input) {
return input.list();
}
}));
}
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
Cheers
Hi Dragan
Great! Why not blog it
and add a link or just add your code in a comment. It will help readers.
Thanks Dragan, I have added your comment(code) to the bottom of the post
[...] Tapestry5 Grid component [...]