Package org.apache.velocity.tools.view

Class PagerTool

  • Direct Known Subclasses:
    AbstractPagerTool, AbstractSearchTool
    @DefaultKey("pager")
@InvalidScope({"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:
    $Revision$ $Date$
    Author:
    Nathan Bubna

    • Field Detail

      • 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 javax.servlet.http.HttpSession session

    • Constructor Detail

      • PagerTool

        public PagerTool()

    • Method Detail

      • 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.

      • 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:
        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