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

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。