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/**
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* Copyright (C) 2012 EDIT
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* European Distributed Institute of Taxonomy
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* http://www.e-taxonomy.eu
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*
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* The contents of this file are subject to the Mozilla Public License Version 1.1
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* See LICENSE.TXT at the top of this package for the full license terms.
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*/
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package eu.etaxonomy.cdm.api.service.pager;
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import java.util.List;
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import eu.etaxonomy.cdm.api.service.pager.impl.AbstractPagerImpl;
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/**
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* @see also class <code>eu.etaxonomy.cdm.remote.controller.util.PagerParameter</code>
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*
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* @author a.kohlbecker
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* @since Dec 10, 2012
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*/
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public class PagerUtils {
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/**
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* Returns the start index for the given page size and page index values
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* by multiplying both values (startFor = pageSize * pageIndex).<BR>
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* If page size is <code>null</code>, either <code>null</code> is returned
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* or an exception is thrown if page index is > 0.
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* If page index is null it is assumed as 0.
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*
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* @param pageSize the page size
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* @param pageIndex the page index
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* @return the start index
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* @throws PagerRangeException if pageSize == null and pageIndex > 0
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*/
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public static Integer startFor(Integer pageSize, Integer pageIndex) throws PagerRangeException {
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if(pageIndex == null) {
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pageIndex = 0;
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}
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if(pageSize == null){
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if (pageIndex > 0 ){
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throw new PagerRangeException("Page index must be undefined or 0 for undefined page size but was " + pageIndex);
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}else{
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return null;
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}
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}
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return pageSize * pageIndex;
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}
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/**
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* Returns the limit value as used in SQL/HQL statements for the given
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* page size.<BR>
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* Earlier, for <code>null</code> the value 0 was returned but as
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* it was decided that pageSize = <code>null</code> should not set any limitation
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* it was changed to return value <code>null</code>. This way the current implementation
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* is the identity function and has no effect except for documentation.
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* <code>null</code> should be handled in dao-s or specialized code such as
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* {@link #pageList(List, Integer, Integer)}.
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*
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* @param pageSize
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* @return
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*/
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public static Integer limitFor(Integer pageSize) {
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if(pageSize == null){
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return null;
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}else{
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return pageSize;
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}
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}
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/**
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* The original method {@link AbstractPagerImpl#hasResultsInRange(Long, Integer, Integer)} is
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* hard to find, therefore this method has been wired also into this Utility class
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* this this is looked up more frequently.
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*
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* @param numberOfResults
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* @param pageIndex
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* @param pageSize
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* @return
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*/
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public static boolean hasResultsInRange(Long numberOfResults, Integer pageIndex, Integer pageSize) {
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return AbstractPagerImpl.hasResultsInRange(numberOfResults, pageIndex, pageSize);
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}
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/**
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* Returns a synchronized (sub)list of fullList which contains only the items
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* for the given page
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* @param fullList
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* @param pageIndex page index
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* @param pageSize page size
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* @return a synchronized list holding the page items
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*/
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public static <T extends Object> List<T> pageList(List<T> fullList, Integer pageIndex, Integer pageSize){
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Integer start = startFor(pageSize, pageIndex);
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if (start == null){
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return fullList;
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}
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Integer limit = limitFor(pageSize); //no effect and never null at this point due to startFor semantics
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limit = Math.min(Integer.MAX_VALUE - start, limit);
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if (fullList.size() > start) {
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Integer toIndex = Math.min(fullList.size(), start + limit);
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return fullList.subList(start, toIndex);
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}else{
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return fullList.subList(fullList.size(), fullList.size()); //empty list
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}
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}
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}
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