大二的计科专业学生,感觉课堂上学的不够,所以自学了jsp+servlet,跟着视频做网上商城和论坛的项目,用的是mvc模式,这当中都涉及到了分页操作,我看完后觉得比较好的是一种是这样的:
先创建JavaBean
import java.util.ArrayList; public class PageBean { private int pageNow;//第几页 private int pageSize;//每页显示几个记录 private int pageCount;//总页数 private int rowCount;//总记录数 private ArrayList al;//该页要显示的记录 public PageBean() { } public int getPageNow() { return pageNow; } public void setPageNow(int pageNow) { this.pageNow = pageNow; } public int getPageSize() { return pageSize; } public void setPageSize(int pageSize) { this.pageSize = pageSize; } public int getPageCount() { return pageCount; } public void setPageCount(int pageCount) { this.pageCount = pageCount; } public int getRowCount() { return rowCount; } public void setRowCount(int rowCount) { this.rowCount = rowCount; } public ArrayList getAl() { return al; } public void setAl(ArrayList al) { this.al = al; } }
然后是一个操作数据库的工具类,其中进行分页的方法是:
//我以对论坛中的帖子分页为例,显示pid=0的帖子并分页,Article是帖子类 public static void getPageInfo(PageBean pb){ int pageNow = pb.getPageNow();//获得要显示的页数 int pageSize = pb.getPageSize();//获得每页显示的记录数 int rowCount = 0; int pageCount = 0; ArrayList al = new ArrayList(); try { ct = getConnection(); ps=ct.prepareStatement("select top "+pageSize +" * from article where pid = 0 and id not in (select top " +pageSize*(pageNow-1)+" id from article where pid = 0) "); rs = ps.executeQuery(); while (rs.next()){ Article article= new Article(); article.setId(rs.getInt(1)); article.setPid(rs.getInt(2)); article.setRootId(rs.getInt(3)); article.setTitle(rs.getString(4)); article.setCont(rs.getString(5)); article.setPdate(rs.getTimestamp(6)); article.setIsLeaf(rs.getInt(7)); al.add(article); } pb.setAl(al);//赋值要显示页的记录 ps = ct.prepareStatement("select count(*) from article where pid = 0"); rs = ps.executeQuery(); if (rs.next()){ rowCount = rs.getInt(1);//得到记录总数 } pageCount = (rowCount - 1) / pageSize + 1;//得到页总数 pb.setPageCount(pageCount); pb.setRowCount(rowCount); } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e.getMessage()); } finally { close(rs, ps, ct); } }
在昨天晚上,我突然想到了另外一种思路:
//我换了另一种思路,就是先把pid=0的帖子都取出来,再取出其中要显示页的记录封装到ArrayList中 //上面一种是先把要显示页的记录取出来,再把记录封装到ArrayList中 public static void getPageInfo(PageBean pb){ int pageNow = pb.getPageNow();//获得要显示的页数 int pageSize = pb.getPageSize();//获得每页显示的记录数 int rowCount = 0; int pageCount = 0; ArrayList al = new ArrayList(); try { ct = getConnection(); ps=ct.prepareStatement("select * from article pid = 0"); rs = ps.executeQuery(); int startPos = (pageNow - 1 ) * pageSize; int i = 0; while (rs.next()){ if (i == startPos){ for (int j = 0; j < pageSize; j++){ Article article= new Article(); article.setId(rs.getInt(1)); article.setPid(rs.getInt(2)); article.setRootId(rs.getInt(3)); article.setTitle(rs.getString(4)); article.setCont(rs.getString(5)); article.setPdate(rs.getTimestamp(6)); article.setIsLeaf(rs.getInt(7)); al.add(article); if (!rs.next()){ break; } } break; } i++; } pb.setAl(al);//赋值要显示页的记录 ps = ct.prepareStatement("select count(*) from article where pid = 0"); rs = ps.executeQuery(); if (rs.next()){ rowCount = rs.getInt(1);//得到记录总数 } pageCount = (rowCount - 1) / pageSize + 1;//得到页总数 pb.setPageCount(pageCount); pb.setRowCount(rowCount); } catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e.getMessage()); } finally { close(rs, ps, ct); } }
使用举例:
int pageNow = 1; int pageSize = 4; String pagenow = request.getParameter("pageNow"); if (pagenow != null){ pageNow = Integer.parseInt(pagenow); } PageBean pb = new PageBean(); pb.setPageNow(pageNow); pb.setPageSize(pageSize); SqlHelper.getPageInfo(pb); request.setAttribute("pagebean", pb); request.getRequestDispatcher("/XXX.jsp").forward(request, response);
上述就是我对分页操作的一点想法,一种是先把pid=0的帖子都取出来,再取出其中要显示页的记录封装到ArrayList中,另一种是先把要显示页的记录取出来,再把记录封装到ArrayList中。不知道实际开发中是怎么进行分页操作的,这仅是我自学后的一点点思考,希望前辈们给我点意见。