org.pajes.db.entity
Class PagingLister

java.lang.Object
  org.pajes.db.entity.MaintenanceDisplayElement
      org.pajes.db.entity.Lister
          org.pajes.db.entity.PagingLister

All Implemented Interfaces:

java.lang.Cloneable

Direct Known Subclasses:

DefaultLister

public abstract class PagingLister

extends Lister

Abstract super-class of all classes that create a Paje with a list of Entity objects, that support showing a subset of all Entity objects and paging through the subsets.

All sub-classes MUST have a no-parameter constructor.

Field Summary

static java.lang.String	FIRST_LIST_VALUE The value ("f") of the LIST_PARAMETER that indicates that the request is to display the first page of the list.
static java.lang.String	LAST_LIST_VALUE The value ("l") of the LIST_PARAMETER that indicates that the request is to display the last page of the list.
static java.lang.String	LIST_PARAMETER The name ("_l_") of the request parameter that determines which subset of the Entity objects will be displayed on this invocation.
static java.lang.String	NEXT_LIST_VALUE The value ("n") of the LIST_PARAMETER that indicates that the request is to display the next page of the list.
static java.lang.String	PREVIOUS_LIST_VALUE The value ("p") of the LIST_PARAMETER that indicates that the request is to display the previous page of the list.
static java.lang.String	ROWS_PARAMETER The name ("rows_parameter") of the request parameter that determines the number of Entity objects will be displayed on a page.

Fields inherited from class org.pajes.db.entity.Lister

SEARCH_ATTRIBUTE_SUFFIX, SEARCH_PARAMETER, SEARCH_PARAMETER_VALUE, SORT_ATTRIBUTE_SUFFIX, SORT_PARAMETER

Constructor Summary

PagingLister()

Method Summary

protected int	getFirstIndex() Returns the index in the result set of the first Entity to be displayed on the page.
protected int	getLastIndex() Returns the index in the result set of the last Entity displayed on the page.
protected int	getLastPageNumber() Convenience method to return the last page number.
protected int	getPageNumber() Convenience method to return the current page number.
protected int	getPageSize() Returns the maximum number of rows that will be displayed on each page.
protected int	getSetSize() Returns the number of rows in the total result set.
void	init(Manager manager, javax.servlet.ServletContext context) Initialises the PagingLister.
protected Entity[]	retrieveSet() Returns the set of Entity objects to be displayed in the list.
protected void	setFirstIndex(int first) Places the index in the result set of the first Entity displayed on the page into the HttpSession.
protected void	setPageSize(int rows) Sets the number of rows that will be displayed on each page.

Methods inherited from class org.pajes.db.entity.Lister

build, getAnchor, getBaseAnchor, getHeaderRowCount, getPaje, getRow, getScope, getSearchAttributeName, getSortAttributeName, init, onCell, onFirstRow, onLastRow, onRow, setNullDisplay, useQualifiedColumnNamesInScope

Methods inherited from class org.pajes.db.entity.MaintenanceDisplayElement

clone, getManager, getRequest, getServletContext, init, isInitialised, setRequest

Methods inherited from class java.lang.Object

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

Field Detail

FIRST_LIST_VALUE

public static final java.lang.String FIRST_LIST_VALUE

The value ("f") of the LIST_PARAMETER that indicates that the request is to display the first page of the list.

See Also:

Constant Field Values

LAST_LIST_VALUE

public static final java.lang.String LAST_LIST_VALUE

The value ("l") of the LIST_PARAMETER that indicates that the request is to display the last page of the list.

See Also:

Constant Field Values

LIST_PARAMETER

public static final java.lang.String LIST_PARAMETER

The name ("_l_") of the request parameter that determines which subset of the Entity objects will be displayed on this invocation.

The parameter value must be one of:

• FIRST_LIST_VALUE
• LAST_LIST_VALUE
• NEXT_LIST_VALUE
• PREVIOUS_LIST_VALUE
• a number indicating the index of the first record in the result set to be displayed on the page.

See Also:

Constant Field Values

NEXT_LIST_VALUE

public static final java.lang.String NEXT_LIST_VALUE

The value ("n") of the LIST_PARAMETER that indicates that the request is to display the next page of the list. If no LIST_PARAMETER is specified, this is the default.

See Also:

Constant Field Values

PREVIOUS_LIST_VALUE

public static final java.lang.String PREVIOUS_LIST_VALUE

The value ("p") of the LIST_PARAMETER that indicates that the request is to display the previous page of the list.

See Also:

Constant Field Values

ROWS_PARAMETER

public static final java.lang.String ROWS_PARAMETER

The name ("rows_parameter") of the request parameter that determines the number of Entity objects will be displayed on a page.

See Also:

Constant Field Values

Constructor Detail

PagingLister

public PagingLister()

Method Detail

init

public void init(Manager manager,
                 javax.servlet.ServletContext context)
          throws java.io.IOException

Initialises the PagingLister.

Sub-classes should not over-ride this method. Instead, sub-classes should over-ride the Lister.init(org.pajes.db.entity.Manager, javax.servlet.ServletContext, javax.servlet.http.HttpServletRequest) method, which is called automatically by this method. If this method is over-rdden, the sub-class MUST call super.init(manager, context, request) to correctly iniitalise the lister.

Overrides:

init in class Lister

Parameters:

manager - the Manager that manages the Entity objects to be listed.

context - the ServletContext.

Throws:

java.io.IOException - if an IO exception occurs.

setFirstIndex

protected void setFirstIndex(int first)
                      throws java.lang.IndexOutOfBoundsException,
                             java.sql.SQLException

Places the index in the result set of the first Entity displayed on the page into the HttpSession.

Parameters:

first - the index in the result set of the first Entity to be displayed.

Throws:

java.lang.IndexOutOfBoundsException - if the argument is less than 1.

java.sql.SQLException - if an error occurs determining the set size.

getFirstIndex

protected int getFirstIndex()
                     throws java.sql.SQLException

Returns the index in the result set of the first Entity to be displayed on the page.

Returns:

the index in the result set of the first Entity to be displayed.

Throws:

java.sql.SQLException - if an error occurs determining the set size.

getLastIndex

protected int getLastIndex()
                    throws java.sql.SQLException

Returns the index in the result set of the last Entity displayed on the page.

Returns:

the index in the result set of the last Entity displayed.

Throws:

java.sql.SQLException - if an error occurs determining the set size.

getLastPageNumber

protected int getLastPageNumber()
                         throws java.sql.SQLException

Convenience method to return the last page number. The following formula is used:

   return (this.getSetSize() / this.getPageSize()) + 1;
 

Returns:

the last page number.

Throws:

java.sql.SQLException - if an error occurs determining the set size.

getPageNumber

protected int getPageNumber()
                     throws java.sql.SQLException

Convenience method to return the current page number. The following formula is used:

   return (this.getFirstIndex() / this.getPageSize()) + 1;
 

Returns:

the current page number.

Throws:

java.sql.SQLException - if an error occurs determining the set size.

setPageSize

protected void setPageSize(int rows)

Sets the number of rows that will be displayed on each page. If not specified, the default is 20 rows.

This default value may be over-ridden in the web application deployment descriptor. To set the default value, create a <context-param> with a <param-name> of org.pajes.db.entity.PagingLister.pageSize and a <param-value> containing the text. For example:

   <context-param>
       <param-name>org.pajes.db.entity.PagingLister.pageSize</param-name>
       <param-value>20</param-value>
   </context-param>
 

Parameters:

rows - The new page size value.

getPageSize

protected int getPageSize()

Returns the maximum number of rows that will be displayed on each page.

Returns:

the maximum number of rows on a page.

getSetSize

protected int getSetSize()
                  throws java.sql.SQLException

Returns the number of rows in the total result set.

Returns:

The number of rows in the total result set.

Throws:

java.sql.SQLException - if an error occurs determining the set size.

retrieveSet

protected Entity[] retrieveSet()
                        throws java.sql.SQLException

Returns the set of Entity objects to be displayed in the list.

The default implementation returns a maximum of getPageSize() entities that meet the scope, starting with the getFirstIndex(). It then updates the HttpSession with getFirstIndex().

Overrides:

retrieveSet in class Lister

Returns:

the array of Entity objects to be displayed in the list.

Throws:

java.sql.SQLException - if an error occurs retrieving the Entity objects.

See Also:

Lister.getScope()