Paginator


1   //
2   //                                   ____.
3   //                       __/\ ______|    |__/\.     _______
4   //            __   .____|    |       \   |    +----+       \
5   //    _______|  /--|    |    |    -   \  _    |    :    -   \_________
6   //   \\______: :---|    :    :           |    :    |         \________>
7   //           |__\---\_____________:______:    :____|____:_____\
8   //                                      /_____|
9   //
10  //                 . . . i n   j a h i a   w e   t r u s t . . .
11  //
12  //
13  //  Paginator
14  //
15  //
16  
17  package org.jahia.utils.pagination;
18  
19  import java.util.List  ;
20  
21  import javax.servlet.http.HttpServletRequest  ;
22  import javax.servlet.http.HttpServletResponse  ;
23  import javax.servlet.http.HttpSession  ;
24  
25  import org.jahia.utils.JahiaConsole;
26  
27  /**
28   * Paginates a list for partial display (i.e. showing only a window of the 
29   * list elements at a time).
30   *
31   * @author MJ
32   */
33  public class Paginator
34  {
35  
36      /**
37       * The context key used to add the total numbner of items in the list.
38       */
39      public static final String   TOTAL_ITEMS = "totalItems";
40  
41      /**
42       * The context key used to retrieve the current page number.
43       */
44      public static final String   PAGE_KEY = "paginated_page";
45  
46      /**
47       * The context key used to add the previous page number.
48       */
49      public static final String   PREV_PAGE = "prevPage";
50  
51      /**
52       * The context key used to add the current page number.
53       */
54      public static final String   CUR_PAGE = "currentPage";
55  
56      /**
57       * The context key used to add the next page number.
58       */
59      public static final String   NEXT_PAGE = "nextPage";
60  
61      /**
62       * The context key used to add the list of page numbers.
63       */
64      public static final String   PAGES = "pages";
65  
66      /**
67       * Handles paging of the list in cases where the list represents all
68       * items avaliable.
69       */
70      public static List   paginate (List                   items,
71                                   int                  nbrItemsPerPage,
72                                   HttpServletRequest     request,
73                                   HttpServletResponse    response,
74                                   HttpSession            session )
75      {
76          return paginate(items, items.size(), nbrItemsPerPage, request, response, session);
77      }
78  
79      /**
80       * Handles paging of the list in cases where there may be more items
81       * total than are in the list (eg. if some items were filtered out
82       * due to a query).
83       */
84      public static List   paginate ( List                   items,
85                                    int                  totalNbrItems,
86                                    int                  nbrItemsPerPage,
87                                    HttpServletRequest     request,
88                                    HttpServletResponse    response,
89                                    HttpSession            session )
90      {
91          session.setAttribute(TOTAL_ITEMS, new Integer  (totalNbrItems));
92          JahiaConsole.println("Paginator",  "totalNbrItems=" + totalNbrItems);
93  
94          if (totalNbrItems > 0) {
95              int nbrPages = getNbrPages(nbrItemsPerPage, totalNbrItems);
96              JahiaConsole.println("Paginator",  "nbrPages=" + nbrPages);
97  
98              if (nbrPages > 1) {
99                  int curPageNbr = getCurrentPageNbr(request, response, session, nbrPages);
100                 session.setAttribute(CUR_PAGE, new Integer  (curPageNbr));
101 
102                 // Create the page links.
103                 Integer  [] pages = new Integer  [nbrPages];
104                 for (int i = 0; i < nbrPages; i++) {
105                     pages[i] = new Integer  (i + 1);
106                 }
107                 session.setAttribute(PAGES, pages);
108                 session.setAttribute(PREV_PAGE, 
109                             (curPageNbr > 1 ? 
110                              new Integer  (curPageNbr - 1) : null));
111                 session.setAttribute(NEXT_PAGE, 
112                             (curPageNbr < nbrPages ? 
113                              new Integer  (curPageNbr + 1) : null));
114 
115                 // Get the subset of items to display.
116                 items = getPage(items, curPageNbr, nbrItemsPerPage);
117             }
118         }
119         else
120         {
121             items = null;
122         }
123 
124         return items;
125     }
126 
127     /**
128      * Returns a valid page number for the page to display.
129      *
130      * @param session  The session to pull the page number from.
131      * @param nbrPages The highest possible page number.
132      */
133     private static final int getCurrentPageNbr ( HttpServletRequest     request,
134                                                  HttpServletResponse    response,
135                                                  HttpSession            session,
136                                                  int                  nbrPages )
137     {
138         String   page = request.getParameter(PAGE_KEY);
139         int pgNbr = (page != null ? Integer.parseInt(page) : 1);
140         if (pgNbr < 1) {
141             pgNbr = 1;
142         } else if (pgNbr > nbrPages) {
143             pgNbr = nbrPages;
144         }
145         return pgNbr;
146     }
147 
148     /**
149      * Calculates the number of pages based on the number of items.
150      *
151      * @param nbrItemsPerPage The number of items to display per page.
152      * @param nbrItems        The total number of items.
153      * @return                The number of pages to display items on.
154      */
155     protected static final int getNbrPages (int nbrItemsPerPage, int nbrItems)
156     {
157         // The cast is to assure the division returns a float.
158         return (int)Math.ceil((float)nbrItems / nbrItemsPerPage);
159     }
160 
161     /**
162      * Gets the sub list of items to display for the current page.
163      *
164      * @param items           The complete list of items.
165      * @param pgNbr           The current page number.
166      * @param nbrItemsPerPage The number of items to display per page.
167      */
168     protected static final List   getPage (List   items, int pgNbr, 
169                                        int nbrItemsPerPage)
170     {
171         return items.subList
172             ((pgNbr - 1) * nbrItemsPerPage, 
173              Math.min(pgNbr * nbrItemsPerPage, items.size()));
174     }
175 
176     /**
177      * Quick and dirty function to take a type of thing being
178      * searched for and turning it into an SQL regular expression.
179      */
180     protected static String   makeSQLRegex(String   type, String   searchFor)
181     {
182         if (type == null) type = "Contains";
183         if (type.equals("Contains") || type.equals("StartsWith"))
184             searchFor = searchFor + "%";
185         if (type.equals("Contains") || type.equals("EndsWith"))
186             searchFor = "%" + searchFor;   
187         return searchFor;
188     }
189 }
190
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