DataModel (Java EE 5 SDK)

javax.faces.model Class DataModel

java.lang.Object
  javax.faces.model.DataModel

直接已知子类:

ArrayDataModel, ListDataModel, ResultDataModel, ResultSetDataModel, ScalarDataModel

public abstract class DataModel

extends Object

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 UIData.

The data collection underlying a 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 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 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.

DataModel

public DataModel()

isRowAvailable

public abstract boolean isRowAvailable()

Return a flag indicating whether there is rowData available at the current rowIndex. If no wrappedData is available, return false.

抛出异常:

FacesException - if an error occurs getting the row availability

getRowCount

public abstract int getRowCount()

Return the number of rows of data objects represented by this DataModel. If the number of rows is unknown, or no wrappedData is available, return -1.

抛出异常:

FacesException - if an error occurs getting the row count

getRowData

public abstract Object getRowData()

Return an object representing the data for the currenty selected row index. If no wrappedData is available, return null.

抛出异常:

FacesException - if an error occurs getting the row data

IllegalArgumentException - if now row data is available at the currently specified row index

getRowIndex

public abstract int getRowIndex()

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.

抛出异常:

FacesException - if an error occurs getting the row index

setRowIndex

public abstract void setRowIndex(int rowIndex)

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 DataModelEvent will be sent to the rowSelected() method of all registered DataModelListeners.

参数:

rowIndex - The new zero-relative index (must be non-negative)

抛出异常:

FacesException - if an error occurs setting the row index

IllegalArgumentException - if rowIndex is less than -1

getWrappedData

public abstract Object getWrappedData()

Return the object representing the data wrapped by this DataModel, if any.

setWrappedData

public abstract void setWrappedData(Object data)

Set the object representing the data collection wrapped by this DataModel. If the specified data is null, detach this 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 DataModelEvent must be sent to the rowSelected() method of all registered DataModelListeners indicating that this row is now selected.

参数:

data - Data collection to be wrapped, or null to detach from any previous data collection

抛出异常:

ClassCastException - if data is not of the appropriate type for this DataModel implementation

addDataModelListener

public void addDataModelListener(DataModelListener listener)

Add a new DataModelListener to the set interested in notifications from this DataModel.

参数:

listener - The new DataModelListener to be registered

抛出异常:

NullPointerException - if listener is null

getDataModelListeners

public DataModelListener[] getDataModelListeners()

Return the set of DataModelListeners interested in notifications from this DataModel. If there are no such listeners, an empty array is returned.

removeDataModelListener

public void removeDataModelListener(DataModelListener listener)

Remove an existing DataModelListener from the set interested in notifications from this DataModel.

参数:

listener - The old DataModelListener to be deregistered

抛出异常:

NullPointerException - if listener is null

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