javax.faces.model.DataModel Maven / Gradle / Ivy
/*
* $Id: DataModel.java,v 1.20 2007/04/27 22:00:09 ofung Exp $
*/
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package javax.faces.model;
import java.util.ArrayList;
import java.util.List;
import javax.faces.FacesException;
import javax.faces.component.UIData;
/**
* DataModel is an abstraction around arbitrary data
* binding technologies that can be used to adapt a variety of data sources
* for use by JavaServer Faces components that support per-row processing
* for their child components (such as {@link UIData}.
*
* The data collection underlying a {@link DataModel} instance is
* modeled as a collection of row objects that can be accessed by
* a zero-relative cursor (row index). The APIs provide mechanisms to
* position to a specified zero-relative row index, and to retrieve an
* object that represents the data that corresponds to the current
* row index.
*
* A concrete {@link DataModel} instance is attached to a particular
* collection of underlying data by calling the setWrappedData()
* method. It can be detached from that underlying data collection by
* passing a null parameter to this method.
*
* Concrete {@link DataModel} implementations must provide a public
* zero-arguments constructor that calls setWrappedData(null).
* A convenience constructor that takes a wrapped object of the appropriate
* type (and passes it on via a call to setWrappedData(),
* should also be provided.
*
* Event listeners may be registered to receive notifications
* of when a new row index is selected.
*/
public abstract class DataModel {
private static final DataModelListener[] EMPTY_DATA_MODEL_LISTENER =
new DataModelListener[0];
// -------------------------------------------------------------- Properties
/**
* Return a flag indicating whether there is rowData
* available at the current rowIndex. If no
* wrappedData is available, return false.
*
* @throws FacesException if an error occurs getting the row availability
*/
public abstract boolean isRowAvailable();
/**
* Return the number of rows of data objects represented by this
* {@link DataModel}. If the number of rows is unknown, or no
* wrappedData is available, return -1.
*
* @throws FacesException if an error occurs getting the row count
*/
public abstract int getRowCount();
/**
* Return an object representing the data for the currenty selected
* row index. If no wrappedData is available, return
* null.
*
* @throws FacesException if an error occurs getting the row data
* @throws IllegalArgumentException if now row data is available
* at the currently specified row index
*/
public abstract Object getRowData();
/**
* Return the zero-relative index of the currently selected row. If
* we are not currently positioned on a row, or no wrappedData
* is available, return -1.
*
* @throws FacesException if an error occurs getting the row index
*/
public abstract int getRowIndex();
/**
* Set the zero-relative index of the currently selected row, or -1
* to indicate that we are not positioned on a row. It is
* possible to set the row index at a value for which the underlying data
* collection does not contain any row data. Therefore, callers may
* use the isRowAvailable() method to detect whether row data
* will be available for use by the getRowData() method.
*
* If there is no wrappedData available when this method
* is called, the specified rowIndex is stored (and may be
* retrieved by a subsequent call to getRowData()), but no
* event is sent. Otherwise, if the currently selected row index is
* changed by this call, a {@link DataModelEvent} will be sent to the
* rowSelected() method of all registered
* {@link DataModelListener}s.
*
* @param rowIndex The new zero-relative index (must be non-negative)
*
* @throws FacesException if an error occurs setting the row index
* @throws IllegalArgumentException if rowIndex
* is less than -1
*/
public abstract void setRowIndex(int rowIndex);
/**
* Return the object representing the data wrapped by this
* {@link DataModel}, if any.
*/
public abstract Object getWrappedData();
/**
* Set the object representing the data collection wrapped by this
* {@link DataModel}. If the specified data is
* null, detach this {@link DataModel} from any previously
* wrapped data collection instead.
*
* If data is non-null, the currently selected
* row index must be set to zero, and a {@link DataModelEvent} must be sent
* to the rowSelected() method of all registered
* {@link DataModelListener}s indicating that this row is now selected.
*
* @param data Data collection to be wrapped, or null to
* detach from any previous data collection
*
* @throws ClassCastException if data is not of the
* appropriate type for this {@link DataModel} implementation
*/
public abstract void setWrappedData(Object data);
// ------------------------------------------------------ Instance Variables
/**
* The list of registered {@link DataModelListener}s for this
* {@link DataModel}. This variable will be null unless
* there is at least one registered listener.
*/
private List listeners = null;
// --------------------------------------------- Event Listener Registration
/**
* Add a new {@link DataModelListener} to the set interested in
* notifications from this {@link DataModel}.
*
* @param listener The new {@link DataModelListener} to be registered
*
* @throws NullPointerException if listener
* is null
*/
public void addDataModelListener(DataModelListener listener) {
if (listener == null) {
throw new NullPointerException();
}
if (listeners == null) {
//noinspection CollectionWithoutInitialCapacity
listeners = new ArrayList();
}
listeners.add(listener);
}
/**
* Return the set of {@link DataModelListener}s interested in
* notifications from this {@link DataModel}. If there are no such
* listeners, an empty array is returned.
*/
public DataModelListener[] getDataModelListeners() {
if (listeners == null) {
return EMPTY_DATA_MODEL_LISTENER;
} else {
return listeners.toArray
(new DataModelListener[listeners.size()]);
}
}
/**
* Remove an existing {@link DataModelListener} from the set
* interested in notifications from this {@link DataModel}.
*
* @param listener The old {@link DataModelListener} to be deregistered
*
* @throws NullPointerException if listener
* is null
*/
public void removeDataModelListener(DataModelListener listener) {
if (listener == null) {
throw new NullPointerException();
}
if (listeners != null) {
listeners.remove(listener);
if (listeners.isEmpty()) {
listeners = null;
}
}
}
}