Class PagerTool

java.lang.Object
org.apache.velocity.tools.generic.SafeConfig
org.apache.velocity.tools.view.PagerTool
Direct Known Subclasses:
AbstractSearchTool
@DefaultKey("pager") @InvalidScope({"application","session"}) public class PagerTool extends org.apache.velocity.tools.generic.SafeConfig

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<br>
  1. foo<br>
  2. bar<br>
  3. blah<br>
  4. woogie<br>
  5. baz<br><br>
  <b>1</b> <a href="">2</a> <a href="">Next</a>

Example tools.xml configuration:

<tools>
  <toolbox scope="request">
    <tool class="org.apache.velocity.tools.view.PagerTool"/>
  </toolbox>
</tools>
Since:
VelocityTools 2.0
Version:
$Revision$ $Date$
Author:
Nathan Bubna

  • Field Details

    • DEFAULT_NEW_ITEMS_KEY

      public static final String DEFAULT_NEW_ITEMS_KEY
      See Also:

    • DEFAULT_INDEX_KEY

      public static final String DEFAULT_INDEX_KEY
      See Also:

    • DEFAULT_ITEMS_PER_PAGE_KEY

      public static final String DEFAULT_ITEMS_PER_PAGE_KEY
      See Also:

    • DEFAULT_SLIP_SIZE_KEY

      public static final String DEFAULT_SLIP_SIZE_KEY
      See Also:

    • DEFAULT_ITEMS_PER_PAGE

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

    • DEFAULT_SLIP_SIZE

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

    • STORED_ITEMS_KEY

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

    • session

      protected javax.servlet.http.HttpSession session

  • Constructor Details

    • PagerTool

      public PagerTool()

  • Method Details

    • setRequest

      public void setRequest(javax.servlet.http.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.
      Parameters:
      request - servlet request

    • setup

      public void setup(javax.servlet.http.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:

    • 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.
      Returns:
      number of available pages

    • 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.
      Returns:
      number of items
      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