Gen.java

		BeanItemContainer<P> container = new BeanItemContainer<P>(P.class, ps);

		final GeneratedPropertyContainer gp = new GeneratedPropertyContainer(
				container);
		gp.addGeneratedProperty("Col1", new PropertyValueGenerator<String>() {

			@Override
			public SortOrder[] getSortProperties(SortOrder order) {
				return new SortOrder[] { new SortOrder("Col1", order
						.getDirection()) };
			}

			@Override
			public String getValue(Item item, Object itemId, Object propertyId) {
				return apply(((P) itemId).getVal());
			}

			@Override
			public Class<String> getType() {
				return String.class;
			}
		});

		container.setItemSorter(new DefaultItemSorter() {
			@Override
			public void setSortProperties(Sortable container,
					Object[] propertyId, boolean[] ascending) {
				super.setSortProperties(gp, propertyId, ascending);
			}
		});

		grid.setContainerDataSource(gp);