org.apache.tapestry5.grid

Interface GridDataSource

All Known Implementing Classes:

CollectionGridDataSource, HibernateGridDataSource, JpaGridDataSource, NullDataSource

public interface GridDataSource

Defines how a Grid component (and its sub-components) gain access to the row data that is displayed on the page. In many cases, this is just a wrapper around a simple List, but the abstractions exist to support access to a large data set that is accessible in sections.

Method Summary

Modifier and Type	Method and Description
int	getAvailableRows() Returns the number of rows available in the data source.
default int	getAvailableRows(int limit) Return the number of rows available in the data source with an upper limit.
Class	getRowType() Returns the type of value in the rows, or null if not known.
Object	getRowValue(int index) Returns the row value at the provided index.
default boolean	isEmpty() Return whether the data source is empty, i.e.
void	prepare(int startIndex, int endIndex, List<SortConstraint> sortConstraints) Invoked to allow the source to prepare to present values.

Method Detail

isEmpty

default boolean isEmpty()

Return whether the data source is empty, i.e. does not have any rows available.

getAvailableRows

default int getAvailableRows(int limit)

Return the number of rows available in the data source with an upper limit. If determining the total number of rows is expensive, this method should be overridden to provide a more efficient implementation. Please note that the default Grid pager will still determine the total number of rows, so for this to have an effect, a custom pager should be used.

Parameters:

limit - the upper limit

Returns:

the number of rows or limit, whichever is lower

getAvailableRows

int getAvailableRows()

Returns the number of rows available in the data source.

prepare

void prepare(int startIndex,
             int endIndex,
             List<SortConstraint> sortConstraints)

Invoked to allow the source to prepare to present values. This gives the source a chance to pre-fetch data (when appropriate) and informs the source of the desired sort order. Sorting comes first, then extraction by range.

Parameters:

startIndex - the starting index to be retrieved

endIndex - the ending index to be retrieved

sortConstraints - identify how data is to be sorted

getRowValue

Object getRowValue(int index)

Returns the row value at the provided index. This method will be invoked in sequential order. In rare instances, getAvailableRows() may return a different number of rows than are actually available (i.e., the database was changed between calls to getAvailableRows() and the call to prepare(int, int, java.util.List)). In that case, this method should return null for any out-of-range indexes.

getRowType

Class getRowType()

Returns the type of value in the rows, or null if not known. This value is used to create a default BeanModel when no such model is explicitly provided.

Returns:

the row type, or null