News新闻发布系统

News新闻发布系统分页的实现

1.首先我们要在NewsDAO中创建一个方法，返回List<NewsEntity>集合,其中pageIndex表示当前页，pageSize表示新闻数量

public List<NewsEntity> GetSelect(int pageIndex,int pageSize);

2.NewsDAOImpl类实现了NewsDAO，所以自然继承了GetSelect()方法

public List<NewsEntity> GetSelect(int pageIndex,int pageSize)
{
List<NewsEntity> list=new ArrayList<NewsEntity>();
String sql="select top "+pageSize+" * from newsDetial where newsId not in(select top "+(pageIndex-1)*pageSize+" newsId from newsDetial)";
ResultSet rs=executeQuery(sql);
if(rs!=null)
{
    while(rs.next())
   {
　　　　NewsEntity entity=new NewsEntity();
　　　　entity.setNewsId(rs.getInt("newsId"));　　　　entity.setNewsTitle(rs.getString("newsTitle"));                    　　　　entity.setNewsContent(rs.getString("newsContent"));        entity.setNewsCreateDate(rs.getDate("newsCreateDate"));                entity.setNewsAuthor(rs.getString("newsAuthor"));              entity.setNewsCateforyId(rs.getInt("newsCategoryId"));　　　　list.add(entity);
   }
}
    return list;
}    

3.然后我们新建一个Util包，包中有page方法，来存储向用户展示的数据

public class page
{
    //当前页
    private int pageIndex;
    //页面记录数
    private int pageSize;
    //本页显示真实数据
    private List<NewsEntity> list;
    //总页数
    private int totalPages;
    //总记录数
    private int totalRecords;

}

4.在NewsServlet类中，实现其功能(当给总页数赋值时，需要在NewsDAO中新建一个getAllCount方法，在NewsDaoImpl中实现其方法)

public int getAllCount() throws Exception {
            int result=0;
            String sql="select count(1) as num from newsDetails";
            ResultSet rs=executeQuery(sql);
            if(rs!=null)
            {
                if(rs.next())
                {
                    result=rs.getInt("num");
                }
                closeAll();
            }
            return result;
        }

public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
            NewsDAOImpl news=new NewsDAOImpl();
            try {
                page pages=new page();
                //默认显示三条数据
                int pageSize=3;
                pages.setPageSize(pageSize);
                //当前页
                int myIndex;
                String pageIndex=request.getParameter("pageIndex");
                if(pageIndex!=null)
                {
                    myIndex=Integer.parseInt(pageIndex);
                }
                else
                {
                    myIndex=1;
                }
                //给当前页赋值
                pages.setPageIndex(myIndex);
                //总页数
                int mytotalPage=0;
                int totalPage=news.getAllCount();
                if(totalPage%pageSize==0)
                {
                    mytotalPage=totalPage/pageSize;
                }
                else
                {
                    mytotalPage=totalPage/pageSize+1;
                }
                pages.setTotalPages(mytotalPage);
                //查询所有
                //List<NewsEntity> list=news.Select();
                //request.setAttribute("list", list);
                //泛型数据
                List<NewsEntity> list=news.getSelect(pages.getPageIndex(), pageSize);
                pages.setList(list);
                request.setAttribute("list", pages);
                //登录
                String name=request.getParameter("uname");
                String pwd=request.getParameter("upwd");
                boolean flag= news.Login(name, pwd);
                if(flag)
                {

                    response.sendRedirect("newspages/admin.jsp");
                }
                else
                {
                    request.getRequestDispatcher("/index.jsp").forward(request, response);
                }
                request.getRequestDispatcher("/index.jsp").forward(request, response);
                } catch (Exception e) {

                e.printStackTrace();
                }
    }

<ul class="classlist">
        <%
            //从作用域中取出一个泛型
              page page2=  (page)request.getAttribute("list");
            for(NewsEntity item :page2.getList()){
            //一个item就是一个新闻对象

        %>
            <li><a href='<%=path %>/newspages/news_read.jsp'> <%=item.getNewsTitle() %> </a><span> <%=item.getNewsCreateDate() %> </span></li>

       <% }

        %>
        <p align="right"> 当前页数:[<%=page2.getPageIndex() %>/<%=page2.getTotalPages()   %>]&nbsp; <a href="<%=path %>/Servlet/NewsServlet?pageIndex=<%=page2.getPageIndex()+1%>">下一页</a> <a href="#">末页</a> </p>
      </ul>

其中，page2.getPageIndex()代表当前页码，page2.getTotalPages()代表了总页码，当点击下一页的时候page2.getPageIndex()要加1