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package javax.faces.model;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import javax.faces.component.UIData;
/**
* <p><span class="changed_modified_2_0"><strong>DataModel</strong></span>
* 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}.</p>
*
* <p>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.</p>
*
* <p>A concrete {@link DataModel} instance is attached to a particular
* collection of underlying data by calling the <code>setWrappedData()</code>
* method. It can be detached from that underlying data collection by
* passing a <code>null</code> parameter to this method.</p>
*
* <p>Concrete {@link DataModel} implementations must provide a public
* zero-arguments constructor that calls <code>setWrappedData(null)</code>.
* A convenience constructor that takes a wrapped object of the appropriate
* type (and passes it on via a call to <code>setWrappedData()</code>,
* should also be provided.</p>
*
* <p>Event listeners may be registered to receive notifications
* of when a new row index is selected.</p>
*/
public abstract class DataModel<E> implements Iterable<E> {
private static final DataModelListener[] EMPTY_DATA_MODEL_LISTENER =
new DataModelListener[0];
// -------------------------------------------------------------- Properties
/**
* <p>Return a flag indicating whether there is <code>rowData</code>
* available at the current <code>rowIndex</code>. If no
* <code>wrappedData</code> is available, return <code>false</code>.</p>
*
* @throws javax.faces.FacesException if an error occurs getting the row availability
*
* @return true if and only if there is data available at the current index, false otherwise.
*/
public abstract boolean isRowAvailable();
/**
* <p>Return the number of rows of data objects represented by this
* {@link DataModel}. If the number of rows is unknown, or no
* <code>wrappedData</code> is available, return -1.</p>
*
* @throws javax.faces.FacesException if an error occurs getting the row count
*
* @return the number of rows of data represented by this {@code DataModel}
*/
public abstract int getRowCount();
/**
* <p>Return an object representing the data for the currently selected
* row index. If no <code>wrappedData</code> is available, return
* <code>null</code>.</p>
*
* @throws javax.faces.FacesException if an error occurs getting the row data
* @throws IllegalArgumentException if now row data is available
* at the currently specified row index
*
* @return an object representing the data for the currently selected
* row index
*/
public abstract E getRowData();
/**
* <p>Return the zero-relative index of the currently selected row. If
* we are not currently positioned on a row, or no <code>wrappedData</code>
* is available, return -1.</p>
*
* @throws javax.faces.FacesException if an error occurs getting the row index
*
* @return the index of the currently selected row
*/
public abstract int getRowIndex();
/**
* <p>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 <code>isRowAvailable()</code> method to detect whether row data
* will be available for use by the <code>getRowData()</code> method.</p>
*
* <p>If there is no <code>wrappedData</code> available when this method
* is called, the specified <code>rowIndex</code> is stored (and may be
* retrieved by a subsequent call to <code>getRowData()</code>), 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
* <code>rowSelected()</code> method of all registered
* {@link DataModelListener}s.</p>
*
* @param rowIndex The new zero-relative index (must be non-negative)
*
* @throws javax.faces.FacesException if an error occurs setting the row index
* @throws IllegalArgumentException if <code>rowIndex</code>
* is less than -1
*/
public abstract void setRowIndex(int rowIndex);
/**
* <p>Return the object representing the data wrapped by this
* {@link DataModel}, if any.</p>
*
* @return the {@code Object} that this model wraps.
*/
public abstract Object getWrappedData();
/**
* <p>Set the object representing the data collection wrapped by this
* {@link DataModel}. If the specified <code>data</code> is
* <code>null</code>, detach this {@link DataModel} from any previously
* wrapped data collection instead.</p>
*
* <p>If <code>data</code> is non-<code>null</code>, the currently selected
* row index must be set to zero, and a {@link DataModelEvent} must be sent
* to the <code>rowSelected()</code> method of all registered
* {@link DataModelListener}s indicating that this row is now selected.</p>
*
* @param data Data collection to be wrapped, or <code>null</code> to
* detach from any previous data collection
*
* @throws ClassCastException if <code>data</code> is not of the
* appropriate type for this {@link DataModel} implementation
*/
public abstract void setWrappedData(Object data);
// ------------------------------------------------------ Instance Variables
/**
* <p>The list of registered {@link DataModelListener}s for this
* {@link DataModel}. This variable will be <code>null</code> unless
* there is at least one registered listener.</p>
*/
private List<DataModelListener> listeners = null;
// --------------------------------------------- Event Listener Registration
/**
* <p>Add a new {@link DataModelListener} to the set interested in
* notifications from this {@link DataModel}.</p>
*
* @param listener The new {@link DataModelListener} to be registered
*
* @throws NullPointerException if <code>listener</code>
* is <code>null</code>
*/
public void addDataModelListener(DataModelListener listener) {
if (listener == null) {
throw new NullPointerException();
}
if (listeners == null) {
//noinspection CollectionWithoutInitialCapacity
listeners = new ArrayList<>();
}
listeners.add(listener);
}
/**
* <p>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.</p>
*
* @return the listeners for this instance, or an empty array
*/
public DataModelListener[] getDataModelListeners() {
if (listeners == null) {
return EMPTY_DATA_MODEL_LISTENER;
} else {
return listeners.toArray
(new DataModelListener[listeners.size()]);
}
}
/**
* <p>Remove an existing {@link DataModelListener} from the set
* interested in notifications from this {@link DataModel}.</p>
*
* @param listener The old {@link DataModelListener} to be deregistered
*
* @throws NullPointerException if <code>listener</code>
* is <code>null</code>
*/
public void removeDataModelListener(DataModelListener listener) {
if (listener == null) {
throw new NullPointerException();
}
if (listeners != null) {
listeners.remove(listener);
if (listeners.isEmpty()) {
listeners = null;
}
}
}
/**
* <p class="changed_added_2_0">Return a read-only <code>Iterator</code> over the
* row data for this model.</p>
*
* @since 2.0
*/
@Override
public Iterator<E> iterator() {
return new DataModelIterator<>(this);
}
// ---------------------------------------------------------- Nested Classes
@SuppressWarnings({"unchecked"})
private static final class DataModelIterator<T> implements Iterator<T> {
private DataModel<T> model;
private int index;
// -------------------------------------------------------- Constructors
DataModelIterator(DataModel<T> model) {
this.model = model;
this.model.setRowIndex(index);
}
// ----------------------------------------------- Methods from Iterator
/**
* @see java.util.Iterator#hasNext()
*/
@Override
public boolean hasNext() {
return model.isRowAvailable();
}
/**
* @see java.util.Iterator#next()
*/
@Override
public T next() {
if (!model.isRowAvailable()) {
throw new NoSuchElementException();
}
Object o = model.getRowData();
model.setRowIndex(++index);
return (T) o;
}
/**
* Unsupported.
* @see java.util.Iterator#remove()
*/
@Override
public void remove() {
throw new UnsupportedOperationException();
}
} // END DataModelIterator
}