JSP页面分页操作

• 分页操作要点

  • 每页显示的记录数—pageSize
  • 总共的记录数—totalCount
  • 总共页数—totalPage
  • 当前页数—currentPage

• 将要点封装成类: PageUtil

public class PageUtil {
    private int pageSize; // 每页记录数
    private int totalCount; // 总记录数
    private int currentPage; // 当前页数
    private int totalPage; // 总页数

    public int getPageSize() {
        return pageSize;
    }
    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }
    public int getTotalCount() {
        return totalCount;
    }
    public void setTotalCount(int totalCount) {
        this.totalCount = totalCount;
    }
    public int getCurrentPage() {
        return currentPage;
    }
    public void setCurrentPage(int currentPage) {
        this.currentPage = currentPage;
    }
    public int getTotalPage() {
        return totalPage = totalCount % pageSize == 0 ? totalCount / pageSize : (totalCount / pageSize + 1);
    }
    public void setTotalPage(int totalPage) {
        this.totalPage = totalPage;
    }
}

• Mysql数据库分页语句: 通过limit实现

  • limit: index, size: 从下标index开始（从0开始），查询size条记录
  • 示例: 每页显示3条记录，显示第二页记录，mysql语句为limit 3, 3
  • 语句的传参写法: limit (CurrentPage - 1) * PageSize, PageSize

• 修改Dao查询语句

public List<Book> getAll(PageUtil pu) {
    List<Book> list = new ArrayList<Book> ();
    String sql = "select * from book limit ?, ?";

    try {
        ResultSet rs = this.executeQuery(sql, (pu.getCurrentPage() - 1) * pu.getPageSize(), pu.getPageSize());
        while(rs.next()) { // 当rs还有下一个数据时
            // 从rs中取得不同属性，并创建新对象后存入容器
            list.add(new Book(rs.getInt(1), rs.getString(2), rs.getDouble(3), rs.getString(4), rs.getDate(5), rs.getInt(6)));
        }
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        this.close();
    }
    return list;    
}

• 实体Dao查询代码

private void list(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    PageUtil pageUtil = new PageUtil();
    // 设置总共记录数
    pageUtil.setTotalCount(bookDao.count());

    // 设置每页显示数量
    pageUtil.setPageSize(5); 

    //获取当前页数 --- 默认为第一页
    int currentPage = 1;
    if(req.getParameter("currentPage") != null) {
        currentPage = Integer.parseInt(req.getParameter("currentPage"));
    }
    pageUtil.setCurrentPage(currentPage);

    //调用Dao直接查询
    List<Book> list = bookDao.getAll(pageUtil);
    List<Category> clist = categoryDao.getList();
    req.setAttribute("list", list);
    req.setAttribute("clist", clist);
    req.setAttribute("page", pageUtil);
    req.getRequestDispatcher("list.jsp").forward(req, resp);
}

• jsp页面处理

<td colspan=7 align="right">
    <a href="book?op=list&currentPage=${page.currentPage-1 }" 
        <c:if test="${page.currentPage == 1 }">style="color:#ccc" onclick="return false"</c:if>
    >previous</a>
    <c:forEach begin="1" step="1" end="${page.totalPage }" var="pg">
        <a href="book?op=list&currentPage=${pg }">${pg }</a>
    </c:forEach>
    <a href="book?op=list&currentPage=${page.currentPage+1 }"
        <c:if test="${page.currentPage == page.totalPage }">style="color:#ccc" onclick="return false"</c:if>
    >next</a>
    <span>Total ${page.totalPage } pages</span> <%-- 直接取值代表着调用对应的get方法 --%>
    go to<input type="text" id="cp" style="width:15px"/>page<input type="button" value="goto" onclick="search();"/>
</td>


<script>
    function search() {
        var cp = document.getElementById("cp").value;
        location.href = "book?op=list&currentPage=" + cp;
    }
</script>