Package org.apache.tapestry5.internal.grid

# Class NullDataSource

java.lang.Object
org.apache.tapestry5.internal.grid.NullDataSource

All Implemented Interfaces:
  `GridDataSource`

public class NullDataSource extends Object implements GridDataSource
An implementation of `GridDataSource` used when the value null is provided as the source.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `NullDataSource()`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `int`
  `getAvailableRows()`
  Returns the number of rows available in the data source.
  `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.
  `void`
  `prepare(int startIndex, int endIndex, List<SortConstraint> sortConstraints)`
  Invoked to allow the source to prepare to present values.

  ### Methods inherited from class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

  ### Methods inherited from interface org.apache.tapestry5.grid.GridDataSource

  `getAvailableRows, isEmpty`

- ## Constructor Details

  - ### NullDataSource

    public NullDataSource()

- ## Method Details

  - ### getAvailableRows

    public int getAvailableRows()
    Description copied from interface: `GridDataSource`
    Returns the number of rows available in the data source.
    Specified by:
      `getAvailableRows` in interface `GridDataSource`

  - ### getRowType

    public Class getRowType()
    Description copied from interface: `GridDataSource`
    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.
    Specified by:
      `getRowType` in interface `GridDataSource`
    Returns:
      the row type, or null

  - ### prepare

    public void prepare(int startIndex, int endIndex, List<SortConstraint> sortConstraints)
    Description copied from interface: `GridDataSource`
    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.
    Specified by:
      `prepare` in interface `GridDataSource`
    Parameters:
      `startIndex` - the starting index to be retrieved
      `endIndex` - the ending index to be retrieved
      `sortConstraints` - identify how data is to be sorted

  - ### getRowValue

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