org.apache.velocity.tools.view
Class PagerTool

java.lang.Object
  extended by org.apache.velocity.tools.view.PagerTool
Direct Known Subclasses:
AbstractPagerTool, AbstractSearchTool

@DefaultKey(value="pager")
@InvalidScope(value={"application","session"})
public class PagerTool
extends Object

View tool for doing request-based pagination of items in an a list.

Usage:
To use this class, you typically push a List of items to it by putting it in the request attributes under the value returned by getNewItemsKey() (default is "new.items"). You can also set the list of items to be paged in a subclass using the setItems(List) method, or you can always set the item list at another point (even from within the template). This need only happen once per session if a session is available, but the item list can be (re)set as often as you like.

Here's an example of how your subclass would be used in a template:

   #if( $pager.hasItems() )
   Showing $!pager.pageDescription<br>
     #set( $i = $pager.index )
     #foreach( $item in $pager.page )
       ${i}. $!item <br>
       #set( $i = $i + 1 )
     #end
     <br>
     #if ( $pager.pagesAvailable > 1 )
       #set( $pagelink = $link.self.param("show",$!pager.itemsPerPage) )
       #if( $pager.prevIndex )
           <a href="$pagelink.param('index',$!pager.prevIndex)">Prev</a>
       #end
       #foreach( $index in $pager.slip )
         #if( $index == $pager.index )
           <b>$pager.pageNumber</b>
         #else
           <a href="$pagelink.param('index',$!index)">$!pager.getPageNumber($index)</a>
         #end
       #end
       #if( $pager.nextIndex )
           <a href="$pagelink.param('index',$!pager.nextIndex)">Next</a>
       #end
     #end
   #else
   No items in list.
   #end
 
The output of this might look like:

Showing 1-5 of 8
1. foo
2. bar
3. blah
4. woogie
5. baz

1 2 Next

Example tools.xml configuration:

 <tools>
   <toolbox scope="request">
     <tool class="org.apache.velocity.tools.view.PagerTool"/>
   </toolbox>
 </tools>
 

Since:
VelocityTools 2.0
Version:
$Revision: 961796 $ $Date: 2010-07-08 17:18:15 +0200 (jeu., 08 juil. 2010) $
Author:
Nathan Bubna

Field Summary
static String DEFAULT_INDEX_KEY
           
static int DEFAULT_ITEMS_PER_PAGE
          the default number of items shown per page
static String DEFAULT_ITEMS_PER_PAGE_KEY
           
static String DEFAULT_NEW_ITEMS_KEY
           
static int DEFAULT_SLIP_SIZE
          the default max number of page indices to list
static String DEFAULT_SLIP_SIZE_KEY
           
protected  HttpSession session
           
protected static String STORED_ITEMS_KEY
          the key under which items are stored in session
 
Constructor Summary
PagerTool()
           
 
Method Summary
 boolean getCreateSession()
           
 Integer getFirstIndex()
          Returns the index of the first item on the current page of results (as determined by the current index, items per page, and the number of items).
 int getIndex()
          Returns the current search result index.
 String getIndexKey()
           
 List getItems()
          Returns the item list.
 int getItemsPerPage()
          Returns the set number of items to be displayed per page of items
 String getItemsPerPageKey()
           
 Integer getLastIndex()
          Returns the index of the last item on the current page of results (as determined by the current index, items per page, and the number of items).
 String getNewItemsKey()
           
 Integer getNextIndex()
          Returns the index for the next page of items (as determined by the current index, items per page, and the number of items).
 List getPage()
          Returns the current "page" of search items.
 String getPageDescription()
          Returns a description of the current page.
 Integer getPageNumber()
          Returns the "page number" for the current index.
 Integer getPageNumber(int i)
          Returns the "page number" for the specified index.
 int getPagesAvailable()
          Returns the number of pages that can be made from this list given the set number of items per page.
 Integer getPrevIndex()
          Return the index for the previous page of items (as determined by the current index, items per page, and the number of items).
 List getSlip()
          Returns a Sliding List of Indices for Pages of items.
 int getSlipSize()
          Returns the number of result page indices getSlip() will return per request (if available).
 String getSlipSizeKey()
           
protected  List getStoredItems()
          Retrieves stored search items (if any) from the user's session attributes.
 int getTotal()
          Returns the total number of items available.
 boolean hasItems()
          Checks whether or not the result list is empty.
 void reset()
          Sets the item list to null, page index to zero, and items per page to the default.
 void setCreateSession(boolean createSession)
           
 void setIndex(int index)
          Sets the index of the first result in the current page
 void setIndexKey(String key)
           
 void setItems(List items)
          Sets the List to page through.
 void setItemsPerPage(int itemsPerPage)
          Sets the number of items returned in a page of items
 void setItemsPerPageKey(String key)
           
 void setNewItemsKey(String key)
           
 void setRequest(HttpServletRequest request)
          Initializes this tool with the specified HttpServletRequest.
 void setSlipSize(int slipSize)
          Sets the number of result page indices for getSlip() to list.
 void setSlipSizeKey(String key)
           
protected  void setStoredItems(List items)
          Stores current search items in the user's session attributes (if one currently exists) in order to do efficient result pagination.
 void setup(HttpServletRequest request)
          Sets the index, itemsPerPage, and/or slipSize *if* they are set in the request parameters.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

DEFAULT_NEW_ITEMS_KEY

public static final String DEFAULT_NEW_ITEMS_KEY
See Also:
Constant Field Values

DEFAULT_INDEX_KEY

public static final String DEFAULT_INDEX_KEY
See Also:
Constant Field Values

DEFAULT_ITEMS_PER_PAGE_KEY

public static final String DEFAULT_ITEMS_PER_PAGE_KEY
See Also:
Constant Field Values

DEFAULT_SLIP_SIZE_KEY

public static final String DEFAULT_SLIP_SIZE_KEY
See Also:
Constant Field Values

DEFAULT_ITEMS_PER_PAGE

public static final int DEFAULT_ITEMS_PER_PAGE
the default number of items shown per page

See Also:
Constant Field Values

DEFAULT_SLIP_SIZE

public static final int DEFAULT_SLIP_SIZE
the default max number of page indices to list

See Also:
Constant Field Values

STORED_ITEMS_KEY

protected static final String STORED_ITEMS_KEY
the key under which items are stored in session


session

protected HttpSession session
Constructor Detail

PagerTool

public PagerTool()
Method Detail

setRequest

public void setRequest(HttpServletRequest request)
Initializes this tool with the specified HttpServletRequest. This is required for this tool to operate and will throw a NullPointerException if this is not set or is set to null.


setup

public void setup(HttpServletRequest request)
Sets the index, itemsPerPage, and/or slipSize *if* they are set in the request parameters. Likewise, this will set the item list to be paged *if* there is a list pushed into the request attributes under the getNewItemsKey().

Parameters:
request - the current HttpServletRequest

setNewItemsKey

public void setNewItemsKey(String key)

getNewItemsKey

public String getNewItemsKey()

setIndexKey

public void setIndexKey(String key)

getIndexKey

public String getIndexKey()

setItemsPerPageKey

public void setItemsPerPageKey(String key)

getItemsPerPageKey

public String getItemsPerPageKey()

setSlipSizeKey

public void setSlipSizeKey(String key)

getSlipSizeKey

public String getSlipSizeKey()

setCreateSession

public void setCreateSession(boolean createSession)

getCreateSession

public boolean getCreateSession()

reset

public void reset()
Sets the item list to null, page index to zero, and items per page to the default.


setItems

public void setItems(List items)
Sets the List to page through.

Parameters:
items - - the List of items to be paged through

setIndex

public void setIndex(int index)
Sets the index of the first result in the current page

Parameters:
index - the result index to start the current page with

setItemsPerPage

public void setItemsPerPage(int itemsPerPage)
Sets the number of items returned in a page of items

Parameters:
itemsPerPage - the number of items to be returned per page

setSlipSize

public void setSlipSize(int slipSize)
Sets the number of result page indices for getSlip() to list. (for google-ish result page links).

Parameters:
slipSize - - the number of result page indices to list
See Also:
getSlip()

getItemsPerPage

public int getItemsPerPage()
Returns the set number of items to be displayed per page of items

Returns:
current number of items shown per page

getSlipSize

public int getSlipSize()
Returns the number of result page indices getSlip() will return per request (if available).

Returns:
the number of result page indices getSlip() will try to return

getIndex

public int getIndex()
Returns the current search result index.

Returns:
the index for the beginning of the current page

hasItems

public boolean hasItems()
Checks whether or not the result list is empty.

Returns:
true if the result list is not empty.

getItems

public List getItems()
Returns the item list. This is guaranteed to never return null.

Returns:
List of all the items

getLastIndex

public Integer getLastIndex()
Returns the index of the last item on the current page of results (as determined by the current index, items per page, and the number of items). If there is no current page, then null is returned.

Returns:
index for the last item on this page or null if none exists
Since:
VelocityTools 1.3

getNextIndex

public Integer getNextIndex()
Returns the index for the next page of items (as determined by the current index, items per page, and the number of items). If no "next page" exists, then null is returned.

Returns:
index for the next page or null if none exists

getFirstIndex

public Integer getFirstIndex()
Returns the index of the first item on the current page of results (as determined by the current index, items per page, and the number of items). If there is no current page, then null is returned. This is different than getIndex() in that it is adjusted to fit the reality of the items available and is not a mere accessor for the current, user-set index value.

Returns:
index for the first item on this page or null if none exists
Since:
VelocityTools 1.3

getPrevIndex

public Integer getPrevIndex()
Return the index for the previous page of items (as determined by the current index, items per page, and the number of items). If no "next page" exists, then null is returned.

Returns:
index for the previous page or null if none exists

getPagesAvailable

public int getPagesAvailable()
Returns the number of pages that can be made from this list given the set number of items per page.


getPage

public List getPage()
Returns the current "page" of search items.

Returns:
a List of items for the "current page"

getPageNumber

public Integer getPageNumber(int i)
Returns the "page number" for the specified index. Because the page number is used for the user interface, the page numbers are 1-based.

Parameters:
i - the index that you want the page number for
Returns:
the approximate "page number" for the specified index or null if there are no items

getPageNumber

public Integer getPageNumber()
Returns the "page number" for the current index. Because the page number is used for the user interface, the page numbers are 1-based.

Returns:
the approximate "page number" for the current index or null if there are no items

getTotal

public int getTotal()
Returns the total number of items available.

Since:
VelocityTools 1.3

getPageDescription

public String getPageDescription()

Returns a description of the current page. This implementation displays a 1-based range of result indices and the total number of items. (e.g. "1 - 10 of 42" or "7 of 7") If there are no items, this will return "0 of 0".

Sub-classes may override this to provide a customized description (such as one in another language).

Returns:
a description of the current page

getSlip

public List getSlip()
Returns a Sliding List of Indices for Pages of items.

Essentially, this returns a list of item indices that correspond to available pages of items (as based on the set items-per-page). This makes it relativly easy to do a google-ish set of links to available pages.

Note that this list of Integers is 0-based to correspond with the underlying result indices and not the displayed page numbers (see getPageNumber(int)).

Returns:
List of Integers representing the indices of result pages or empty list if there's one or less pages available

getStoredItems

protected List getStoredItems()
Retrieves stored search items (if any) from the user's session attributes.

Returns:
the List retrieved from memory

setStoredItems

protected void setStoredItems(List items)
Stores current search items in the user's session attributes (if one currently exists) in order to do efficient result pagination.

Override this to store search items somewhere besides the HttpSession or to prevent storage of items across requests. In the former situation, you must also override getStoredItems().

Parameters:
items - the List to be stored


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