关于jsp+servlet MVC模式中的分页操作

     我是一名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

 1 import java.util.ArrayList;

 2 

 3 public class PageBean {

 4     private int pageNow;//第几页

 5     private int pageSize;//每页显示几个记录

 6     private int pageCount;//总页数

 7     private int rowCount;//总记录数

 8     private ArrayList al;//该页要显示的记录

 9     

10     public PageBean() {

11         

12     }

13     public int getPageNow() {

14         return pageNow;

15     }

16     public void setPageNow(int pageNow) {

17         this.pageNow = pageNow;

18     }

19     public int getPageSize() {

20         return pageSize;

21     }

22     public void setPageSize(int pageSize) {

23         this.pageSize = pageSize;

24     }

25     public int getPageCount() {

26         return pageCount;

27     }

28     public void setPageCount(int pageCount) {

29         this.pageCount = pageCount;

30     }

31     public int getRowCount() {

32         return rowCount;

33     }

34     public void setRowCount(int rowCount) {

35         this.rowCount = rowCount;

36     }

37     public ArrayList getAl() {

38         return al;

39     }

40     public void setAl(ArrayList al) {

41         this.al = al;

42     }

43     

44 }

然后是一个操作数据库的工具类，其中进行分页的方法是：

 1 //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

 2 public static void getPageInfo(PageBean pb){

 3     int pageNow = pb.getPageNow();//获得要显示的页数

 4     int pageSize = pb.getPageSize();//获得每页显示的记录数

 5     int rowCount = 0;

 6     int pageCount = 0;

 7     ArrayList al = new ArrayList();

 8     try {

 9         ct = getConnection();

10         ps=ct.prepareStatement("select top "+pageSize

11                 +" * from article where  pid = 0 and id not in (select top "

12                 +pageSize*(pageNow-1)+" id from article where pid = 0) ");

13         rs = ps.executeQuery();

14         while (rs.next()){

15             Article article= new Article();

16             article.setId(rs.getInt(1));

17             article.setPid(rs.getInt(2));

18             article.setRootId(rs.getInt(3));

19             article.setTitle(rs.getString(4));

20             article.setCont(rs.getString(5));

21             article.setPdate(rs.getTimestamp(6));

22             article.setIsLeaf(rs.getInt(7));

23             al.add(article);

24         }

25         pb.setAl(al);//赋值要显示页的记录

26         ps = ct.prepareStatement("select count(*) from article where pid = 0");

27         rs = ps.executeQuery();

28         if (rs.next()){

29             rowCount = rs.getInt(1);//得到记录总数

30         }

31         pageCount = (rowCount - 1) / pageSize + 1;//得到页总数

32         pb.setPageCount(pageCount);

33         pb.setRowCount(rowCount);

34     } catch (Exception e) {

35         e.printStackTrace();

36         throw new RuntimeException(e.getMessage());

37     } finally {

38         close(rs, ps, ct);

39     }

40 }

在昨天晚上，我突然想到了另外一种思路：

 1 //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

 2 //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

 3 public static void getPageInfo(PageBean pb){

 4     int pageNow = pb.getPageNow();//获得要显示的页数

 5     int pageSize = pb.getPageSize();//获得每页显示的记录数

 6     int rowCount = 0;

 7     int pageCount = 0;

 8     ArrayList al = new ArrayList();

 9     try {

10         ct = getConnection();

11         ps=ct.prepareStatement("select * from article pid = 0"); 

12         rs = ps.executeQuery();

13         int startPos = (pageNow - 1 ) * pageSize;

14         int i = 0;

15         while (rs.next()){

16             if (i == startPos){

17                 for (int j = 0; j < pageSize; j++){

18                     Article article= new Article();

19                     article.setId(rs.getInt(1));

20                     article.setPid(rs.getInt(2));

21                     article.setRootId(rs.getInt(3));

22                     article.setTitle(rs.getString(4));

23                     article.setCont(rs.getString(5));

24                     article.setPdate(rs.getTimestamp(6));

25                     article.setIsLeaf(rs.getInt(7));

26                     al.add(article);

27                     if (!rs.next()){

28                         break;

29                     }

30                 }

31                 break;

32             }

33             i++;

34         }

35         pb.setAl(al);//赋值要显示页的记录

36         ps = ct.prepareStatement("select count(*) from article where pid = 0");

37         rs = ps.executeQuery();

38         if (rs.next()){

39             rowCount = rs.getInt(1);//得到记录总数

40         }

41         pageCount = (rowCount - 1) / pageSize + 1;//得到页总数

42         pb.setPageCount(pageCount);

43         pb.setRowCount(rowCount);

44     } catch (Exception e) {

45         e.printStackTrace();

46         throw new RuntimeException(e.getMessage());

47     } finally {

48         close(rs, ps, ct);

49     }

50 }

使用举例：

 1 int pageNow = 1;

 2 int pageSize = 4;

 3 String pagenow = request.getParameter("pageNow");

 4 if (pagenow != null){

 5     pageNow = Integer.parseInt(pagenow);

 6 }

 7 PageBean pb = new PageBean();

 8 pb.setPageNow(pageNow);

 9 pb.setPageSize(pageSize);

10 SqlHelper.getPageInfo(pb);

11 request.setAttribute("pagebean", pb);

12 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。