paginatablelist.java

java 写的一个新闻发布系统

//
//                                   ____.
//                       __/\ ______|    |__/\.     _______
//            __   .____|    |       \   |    +----+       \
//    _______|  /--|    |    |    -   \  _    |    :    -   \_________
//   \\______: :---|    :    :           |    :    |         \________>
//           |__\---\_____________:______:    :____|____:_____\
//                                      /_____|
//
//                 . . . i n   j a h i a   w e   t r u s t . . .
//
//
//  PaginatableList
//
//

package org.jahia.utils.pagination;


import java.util.*;
import java.sql.*;

import org.apache.regexp.RE;
import org.apache.regexp.RESyntaxException;
import org.jahia.exceptions.JahiaException;

//------------------------------------------------import com.workingdogs.village.*;

//------------------------------------------------import org.joist.database.*;

/**
 * An abstract class describing a list which can be paginated.
 *
 * @author MJ
 */
abstract public class PaginatableList extends ArrayList
{   
    protected int itemsPerPage;

    /**
     * Returns a sublist of this list, the contents determined by
     * the page requested.
     */
    public List getPage(Integer page) throws SQLException
    {
        int start = firstItem(page);
        int finish = lastItem(page);
        return subList(start,finish);
    }

    /**
     * Prints out an HTML navigation bar for the given page; 
     */
    public String navigationBar(String linkText, Integer page)
    throws SQLException
    {
        boolean prependDots = false;
        boolean appendDots = false;
        int pageNo = page.intValue();
        int pages = numberOfPages();
        int startPage = pageNo - 5;
        if (startPage <= 0) startPage = 1;
        if (startPage > 1) prependDots = true;
        int endPage = pageNo + 4;
        if (endPage < 10) endPage = 10;
        if (endPage > pages) endPage = pages;
        if (endPage < (pages-1)) appendDots = true;
        
        String extra = appendQueryString();
        if (!extra.equals("")) {
            if (linkText.lastIndexOf("?") == -1) {
                linkText += "?";
            } else { 
                linkText += "&"; 
            }
            linkText += extra;
        }

        StringBuffer bar = new StringBuffer();
        if (startPage != endPage) {
            if (pageNo != 1) {
                bar.append(makeLink(linkText, pageNo-1, "Prev"));
            } else {
                bar.append("Prev");
            }
            bar.append(" | ");

            if (prependDots) bar.append(" ... | ");

            for (int i = startPage; i <= endPage; i++) {
                String linkedText = i + " " + makeGuide(new Integer(i));

                if (i == pageNo) {
                    bar.append(linkedText);
                } else {
                    bar.append(makeLink(linkText, i, linkedText));
                }
                if (i < endPage) {
                    bar.append (" | ");
                }
            }

            bar.append(" | ");

            if (prependDots) bar.append(" ... | ");

            if (pageNo != endPage) {
                bar.append(makeLink(linkText, pageNo+1, "Next"));
            } else {
                bar.append("Next");
            }
        }
        return bar.toString();
    }

    /**
     * Makes a link to the given page.
     */    
    protected String makeLink(String linkText, int pageNo, String linkedText)
    {
        StringBuffer link = new StringBuffer();
        link.append("<a href=\"").append(linkText);
        if (linkText.lastIndexOf("?") == -1) {
            link.append("?");
        } else { 
            link.append("&"); 
        }
        link.append("page=").append(pageNo).append("\">").append(linkedText);
        link.append("</a>");
        return link.toString();
    }

    /**
     * Makes a guide to the given page for use in the navbar. A
     * list of Users, for instance, might print "(A-N)" for a page
     * in which the first entry had a name beginning with A and the
     * last entry had a name beginning with N.
     */
    public String makeGuide(Integer page) throws SQLException
    {
        return "";
    }

    /**
     * Generate whatever text is neccessary to mantain this list's
     * state in a link to another page. A list which had had a filter
     * applied to it would need to return fields which would reinstate
     * the filter.
     */
    public String appendQueryString()
    {
        return "";
    }

    /**
     * Returns the number of items in the list.
     */
    public int numberOfItems() throws SQLException
    {
        return size();
    }

    /**
     * Returns the number of pages the list will occupy.
     */
    public int numberOfPages() throws SQLException
    {
        int entries = numberOfItems();
        int pages = entries / itemsPerPage;
        int entriesOnExtraPage = entries % itemsPerPage;
        if (entriesOnExtraPage != 0) pages++;
        return pages;
    }

    /**
     * Returns the maximum number of items that should be on any
     * given page. If the list was created with 0 items per page,
     * display the whole list.
     */
    public int itemsOnPage() throws SQLException
    {
        int itemsOnPage = itemsPerPage;
        if (itemsOnPage == 0) {
            itemsOnPage = numberOfItems();
        }
        return itemsOnPage;
    }

    /**
     * Returns the index of the first item on the given page.
     */
    public int firstItem(Integer pageNo) throws SQLException
    {
        int itemsOnThisPage = itemsOnPage();
        
        int start = ((pageNo.intValue()-1) * itemsOnThisPage);
        if (start >= numberOfItems()) {
            start = 0;
        }
        return start;
    }

    /**
     * Returns the index of the last item on the given page.
     */
    public int lastItem(Integer pageNo) throws SQLException
    {
        int finish = firstItem(pageNo) + itemsOnPage();
        if (finish >= numberOfItems()) {
            finish = numberOfItems();
        }
        return finish;
    }

}