com.cc.framework.ui.model.imp
Class VirtualListDataModel

java.lang.Object
  com.cc.framework.ui.model.imp.VirtualListDataModel

All Implemented Interfaces:

DataModel, ListDataModel, java.io.Serializable, VirtualDataModel

public abstract class VirtualListDataModel

extends java.lang.Object

implements VirtualDataModel, ListDataModel, java.io.Serializable

List Data Model for display lists with a very large or unknown number of rows.

Version:

$Revision: 1.14 $

Author:

Harald Schulz

See Also:

Serialized Form

Field Summary

private boolean	keepRows This flag directs the list not to flush the rowset cache when a new rowset is loaded.
private java.util.Vector	rowset The elements of the currently loaded rowset
private int	rowsetIndex This is the index of the first row in the rowset.
private int	rowsetSize This member holds the size of the rowset.
private static long	serialVersionUID Serial Version UID
private int	size The total number of elements.
private int	threshold Number of overlapping rows between rowsets to reduce page filtering

Constructor Summary

VirtualListDataModel()
Constructor

VirtualListDataModel(int rowsetSize, boolean keepRows)
Constructor

Method Summary

int	capacity() Returns the current capacity of this VirtualListDataModel.
void	clear() Clears the current list
protected void	clearRowset() Removes all elements from the rowset.
protected abstract java.util.Collection	doFetchRowset(int startIndex, int rowCount) This method reads a rowset into memory
protected int	doFetchSize() This method is called to fetch the actual rowset size.
protected void	doSetup() This method is called first to do any initialization processing
private void	fetchRowset(int index) This method is called when the next rowset is to be loaded into memory
java.lang.Object	getElementAt(int index) Returns the (row) object for the specified index.
java.lang.Object	getElementFromRowset(int index) Returns a Element of the rowset
int	getRowsetIndex() Returns the Index of the first element in the rowset
private int	mapIndexToRowSet(int index) This method maps an absolute index to a relative index in the rowset.
void	setRowsetSize(int i) Sets the rowset size to the specified value.
void	setSize(int i) Sets the number of total available elements in this list.
void	setThreshold(int i) Sets the threshold value.
int	size() Returns the number of rows within the list.

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.cc.framework.ui.model.ListDataModel

getUniqueKey

Field Detail

serialVersionUID

private static final long serialVersionUID

Serial Version UID

See Also:

Constant Field Values

keepRows

private boolean keepRows

This flag directs the list not to flush the rowset cache when a new rowset is loaded.

rowsetSize

private int rowsetSize

This member holds the size of the rowset. It should be larger than the number of displayed rows (but that is not necessary)

threshold

private int threshold

Number of overlapping rows between rowsets to reduce page filtering

size

private int size

The total number of elements. -1 when the correct number is unknown

rowsetIndex

private int rowsetIndex

This is the index of the first row in the rowset.

rowset

private java.util.Vector rowset

The elements of the currently loaded rowset

Constructor Detail

VirtualListDataModel

public VirtualListDataModel()

Constructor

VirtualListDataModel

public VirtualListDataModel(int rowsetSize,
                            boolean keepRows)

Constructor

Parameters:

rowsetSize - The number of records that should be fetched at a time

keepRows - Set to true when all rows should be kept in memory. Set to false when only a number of rowsetSize rows should be kept in memory (default)

Method Detail

clear

public void clear()

Clears the current list

clearRowset

protected void clearRowset()

Removes all elements from the rowset. The current rowset index is not affected.

fetchRowset

private void fetchRowset(int index)
                  throws java.lang.Exception

This method is called when the next rowset is to be loaded into memory

Parameters:

index - Start Index

Throws:

java.lang.Exception - Will be thrown in case of an error in the integration layer

doSetup

protected void doSetup()
                throws java.lang.Exception

This method is called first to do any initialization processing

Throws:

java.lang.Exception - Will be thrown in case of an error in the integration layer

doFetchSize

protected int doFetchSize()
                   throws java.lang.Exception

This method is called to fetch the actual rowset size. It's up to the derived class to provide an implementation or not

Returns:

Returns the size of the list or -1

Throws:

java.lang.Exception - Will be thrown in case of an error in the integration layer

doFetchRowset

protected abstract java.util.Collection doFetchRowset(int startIndex,
                                                      int rowCount)
                                               throws java.lang.Exception

This method reads a rowset into memory

Parameters:

startIndex - Index of the first row

rowCount - Number of rows to read

Returns:

Returns a collection of rowbeans

Throws:

java.lang.Exception - Will be thrown in case of an error in the integration layer

mapIndexToRowSet

private int mapIndexToRowSet(int index)
                      throws java.lang.Exception

This method maps an absolute index to a relative index in the rowset. When the relative index is outside the loaded rowset the missing data will be loaded dynamically to match the required index.

Parameters:

index - the absolute index

Returns:

returns the relative index or -1 when the index could not be matched

Throws:

java.lang.Exception - Will be thrown in case of an error in the integration layer

getElementAt

public java.lang.Object getElementAt(int index)

Description copied from interface: ListDataModel

Returns the (row) object for the specified index. This can be a display object (view helper) whose properties will be accessed within the columns of a List- or TreeControl

Specified by:

getElementAt in interface ListDataModel

Parameters:

index - A zero based index

Returns:

A row object.

See Also:

ListDataModel.getElementAt(int)

getElementFromRowset

public java.lang.Object getElementFromRowset(int index)

Returns a Element of the rowset

Parameters:

index - Element index in the rowset

Returns:

Row bean

size

public int size()

Description copied from interface: ListDataModel

Returns the number of rows within the list.

Specified by:

size in interface ListDataModel

Returns:

Number of rows

See Also:

ListDataModel.size()

capacity

public int capacity()

Returns the current capacity of this VirtualListDataModel.

Returns:

the current capacity (the length of its internal data array, kept in the field rowset of this VirtualListDataModel).

setSize

public void setSize(int i)

Sets the number of total available elements in this list.

Parameters:

i - Number of elements or -1 when the number is unknown

getRowsetIndex

public int getRowsetIndex()

Returns the Index of the first element in the rowset

Returns:

Index of the first element in the rowset

setRowsetSize

public void setRowsetSize(int i)

Sets the rowset size to the specified value. It should match the size of a database rowset for optimized data throughput.

Parameters:

i - new rowset size

setThreshold

public void setThreshold(int i)

Sets the threshold value. That is the number of overlapping rows between two adjacent rowsets. The threshold reduces page filtering when the user scrolls through the list.

Parameters:

i - new threshold value