基於hibernate實現的分頁技術

先說明一下基於hibernate實現分頁的原理，假如從數據庫取出100條數據，我們要讓每頁顯示10條，假如從30開始，只需要設置起始位置和最大的返回結果即可

先上代碼：注意傳進來的參數有 Page這類，後面有介紹

public List<Article> queryByPage(final String username, final Page page) {
        return this.getHibernateTemplate().executeFind(new HibernateCallback() {
            public Object doInHibernate(Session session)
                    throws HibernateException, SQLException {
                Query query = session.createQuery("select art from Article art where art.username = ?");
                //設置參數
                query.setParameter(0, username);
                //設置每頁顯示多少個，設置多大結果。
                query.setMaxResults(page.getEveryPage());
                //設置起點
                query.setFirstResult(page.getBeginIndex());
                return query.list();
            }
        });

上面關鍵代碼是 setMaxResults(),和setFirstResult(),即設置最大顯示值和起點

這裏我們需要一個Page工具類，用來操作分頁。

Page.Java

package com.fenye;

public class Page {
    // 1.每頁顯示數量(everyPage)
    private int everyPage;
    // 2.總記錄數(totalCount)
    private int totalCount;
    // 3.總頁數(totalPage)
    private int totalPage;
    // 4.當前頁(currentPage)
    private int currentPage;
    // 5.起始點(beginIndex)
    private int beginIndex;
    // 6.是否有上一頁(hasPrePage)
    private boolean hasPrePage;
    // 7.是否有下一頁(hasNextPage)
    private boolean hasNextPage;

    public Page(int everyPage, int totalCount, int totalPage, int currentPage,
            int beginIndex, boolean hasPrePage, boolean hasNextPage) {
        this.everyPage = everyPage;
        this.totalCount = totalCount;
        this.totalPage = totalPage;
        this.currentPage = currentPage;
        this.beginIndex = beginIndex;
        this.hasPrePage = hasPrePage;
        this.hasNextPage = hasNextPage;
    }

    //構造函數，默認
    public Page(){}

    //構造方法，對所有屬性進行設置


    public int getEveryPage() {
        return everyPage;
    }

    public void setEveryPage(int everyPage) {
        this.everyPage = everyPage;
    }

    public int getTotalCount() {
        return totalCount;
    }

    public void setTotalCount(int totalCount) {
        this.totalCount = totalCount;
    }

    public int getTotalPage() {
        return totalPage;
    }

    public void setTotalPage(int totalPage) {
        this.totalPage = totalPage;
    }

    public int getCurrentPage() {
        return currentPage;
    }

    public void setCurrentPage(int currentPage) {
        this.currentPage = currentPage;
    }

    public int getBeginIndex() {
        return beginIndex;
    }

    public void setBeginIndex(int beginIndex) {
        this.beginIndex = beginIndex;
    }

    public boolean isHasPrePage() {
        return hasPrePage;
    }

    public void setHasPrePage(boolean hasPrePage) {
        this.hasPrePage = hasPrePage;
    }

    public boolean isHasNextPage() {
        return hasNextPage;
    }

    public void setHasNextPage(boolean hasNextPage) {
        this.hasNextPage = hasNextPage;
    }

}

Page工具類主要是封裝頁面信息，一共多少數據啊，一頁顯示多少啊，起點的序號，總頁數，是否有上一頁下一頁，當前頁。

還需要一個操作page的工具類，PageUtil.java

package com.sanqing.fenye;
/*
 * 分頁信息輔助類
 */
public class PageUtil {

    public static Page createPage(int everyPage,int totalCount,int currentPage) {
        everyPage = getEveryPage(everyPage);
        currentPage = getCurrentPage(currentPage);
        int totalPage = getTotalPage(everyPage, totalCount);
        int beginIndex = getBeginIndex(everyPage, currentPage);
        boolean hasPrePage = getHasPrePage(currentPage);
        boolean hasNextPage = getHasNextPage(totalPage, currentPage);
        return new Page(everyPage, totalCount, totalPage, currentPage,
                beginIndex, hasPrePage,  hasNextPage);
    }

    public static Page createPage(Page page,int totalCount) {
        int everyPage = getEveryPage(page.getEveryPage());
        int currentPage = getCurrentPage(page.getCurrentPage());
        int totalPage = getTotalPage(everyPage, totalCount);
        int beginIndex = getBeginIndex(everyPage, currentPage);
        boolean hasPrePage = getHasPrePage(currentPage);
        boolean hasNextPage = getHasNextPage(totalPage, currentPage);
        return new Page(everyPage, totalCount, totalPage, currentPage,
                beginIndex, hasPrePage,  hasNextPage);
    }

    //設置每頁顯示記錄數
    public static int getEveryPage(int everyPage) {
        return everyPage == 0 ? 10 : everyPage;
    }

    //設置當前頁
    public static int getCurrentPage(int currentPage) {
        return currentPage == 0 ? 1 : currentPage;
    }

    //設置總頁數,需要總記錄數，每頁顯示多少
    public static int getTotalPage(int everyPage,int totalCount) {
        int totalPage = 0;
        if(totalCount % everyPage == 0) {
            totalPage = totalCount / everyPage;
        } else {
            totalPage = totalCount / everyPage + 1;
        }
        return totalPage;
    }

    //設置起始點，需要每頁顯示多少，當前頁
    public static int getBeginIndex(int everyPage,int currentPage) {
        return (currentPage - 1) * everyPage;
    }

    //設置是否有上一頁，需要當前頁
    public static boolean getHasPrePage(int currentPage) {
        return currentPage == 1 ? false : true;
    }

    //設置是否有下一個，需要總頁數和當前頁
    public static boolean getHasNextPage(int totalPage, int currentPage) {
        return currentPage == totalPage || totalPage == 0 ? false : true;
    }

}

創建Page只需要3個參數，每頁顯示多少數據，當前頁，總共多少數據，其他的4個參數都可以通過這三個計算出來

所以後面要創建Page，只需要調用這工具方法PageUtil.createPage(3個參數)，就返回一Page.

返回的Page就是前面參數的Page，即要顯示的分頁

這樣就算完成了分頁的功能。