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

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

All Implemented Interfaces:

DataModel, ListDataModel, java.io.Serializable, VirtualDataModel

public abstract class VirtualKeyListDataModel

extends java.lang.Object

implements VirtualDataModel, ListDataModel, java.io.Serializable

List Data Model for Key lists with a very large or unknown number of keys.

Version:

$Revision: 1.7 $

Author:

Harald Schulz

See Also:

Serialized Form

Field Summary

private int	cache The List implements a very simple cache mechanism to prevent unnecessary loading
private java.lang.Object	cacheBean Cached row bean
private boolean	keepKeys This flag directs the list not to flush the keyset cache when a new keyset is loaded.
private java.util.Vector	keyset The elements of the currently loaded keyset
private int	keysetIndex This is the index of the first key in the keyset.
private int	keysetSize This member holds the size of the keyset.
private static long	serialVersionUID Serial Version UID
private int	size The total number of elements.
private int	threshold Number of overlapping keys between keysets to reduce page filtering

Constructor Summary

VirtualKeyListDataModel()
Constructor

VirtualKeyListDataModel(int keysetSize, boolean keepKeys)
Constructor

Method Summary

int	capacity() Returns the current capacity of this VirtualKeyListDataModel.
void	clear() Clears the current list
protected void	clearKeyset() Removes all elements from the keyset.
protected abstract java.util.Collection	doFetchKeyset(int startIndex, int keyCount) This method reads a keyset into memory
protected abstract java.lang.Object	doFetchRowBean(java.lang.Object key) Overwrite this method to load one single row bean
protected int	doFetchSize() This method is called to fetch the actual keyset size.
protected void	doSetup() This method is called first to do any initialization processing
private void	fetchKeyset(int index) This method is called when the next keyset is to be loaded into memory
java.lang.Object	getElementAt(int index) Returns the (row) object for the specified index.
java.lang.Object	getElementFromKeyset(int index) Returns a Element of the keyset
int	getKeysetIndex() Returns the Index of the first element in the keyset
private java.lang.Object	getRowBean(int index) Returns the row bean for the given index
java.lang.String	getUniqueKey(int index) Returns a unique key for the row which is specified by the index.
private int	mapIndexToKeyset(int index) This method maps an absolute index to a relative index in the keyset.
void	setKeysetSize(int i) Sets the keyset size to the specified value.
void	setSize(int i) Sets the number of total available keys 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

Field Detail

serialVersionUID

private static final long serialVersionUID

Serial Version UID

See Also:

Constant Field Values

keepKeys

private boolean keepKeys

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

keysetSize

private int keysetSize

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

threshold

private int threshold

Number of overlapping keys between keysets to reduce page filtering

size

private int size

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

keysetIndex

private int keysetIndex

This is the index of the first key in the keyset.

keyset

private java.util.Vector keyset

The elements of the currently loaded keyset

cache

private int cache

The List implements a very simple cache mechanism to prevent unnecessary loading

cacheBean

private java.lang.Object cacheBean

Cached row bean

Constructor Detail

VirtualKeyListDataModel

public VirtualKeyListDataModel()

Constructor

VirtualKeyListDataModel

public VirtualKeyListDataModel(int keysetSize,
                               boolean keepKeys)

Constructor

Parameters:

keysetSize - The number of keys that should be fetched at a time

keepKeys - Set to true when all keys should be kept in memory. Set to false when only a number of keysetSize keys should be kept in memory (default)

Method Detail

clear

public void clear()

Clears the current list

clearKeyset

protected void clearKeyset()

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

fetchKeyset

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

This method is called when the next keyset 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 keyset 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

doFetchKeyset

protected abstract java.util.Collection doFetchKeyset(int startIndex,
                                                      int keyCount)
                                               throws java.lang.Exception

This method reads a keyset into memory

Parameters:

startIndex - Index of the first key

keyCount - Number of keys to read

Returns:

Returns a collection of keys

Throws:

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

doFetchRowBean

protected abstract java.lang.Object doFetchRowBean(java.lang.Object key)
                                            throws java.lang.Exception

Overwrite this method to load one single row bean

Parameters:

key - The key

Returns:

row bean

Throws:

java.lang.Exception - An error occurred while loading the row bean

mapIndexToKeyset

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

This method maps an absolute index to a relative index in the keyset. When the relative index is outside the loaded keyset 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)

getUniqueKey

public java.lang.String getUniqueKey(int index)

Description copied from interface: ListDataModel

Returns a unique key for the row which is specified by the index. This id will be attached in hyperlinks to identify the row/object. This can be a simple row index or a key which correspond to the primary key from the database.

Specified by:

getUniqueKey in interface ListDataModel

Parameters:

index - A zero based index

Returns:

The unique key

See Also:

ListDataModel.getUniqueKey(int)

getRowBean

private java.lang.Object getRowBean(int index)

Returns the row bean for the given index

Parameters:

index - Element index

Returns:

row bean

getElementFromKeyset

public java.lang.Object getElementFromKeyset(int index)

Returns a Element of the keyset

Parameters:

index - Element index in the keyset

Returns:

Key

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 VirtualKeyListDataModel.

Returns:

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

setSize

public void setSize(int i)

Sets the number of total available keys in this list.

Parameters:

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

getKeysetIndex

public int getKeysetIndex()

Returns the Index of the first element in the keyset

Returns:

Index of the first element in the keyset

setKeysetSize

public void setKeysetSize(int i)

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

Parameters:

i - new keyset size

setThreshold

public void setThreshold(int i)

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

Parameters:

i - new threshold value