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分页程序
liuzaiyao 原创更新：2006-11-10 12:31:43 版本: 1.0

private int currentPage = 1; // 当前页

private int totalPages = 0; // 总页数

private int pageRecorders = 5;// 每页5条数据

private int totalRows = 0; // 总数据数

private int pageStartRow = 0;// 每页的起始数

private int pageEndRow = 0; // 每页显示数据的终止数

private boolean hasNextPage = false; // 是否有下一页

private boolean hasPreviousPage = false; // 是否有前一页

private int nextPage = 0;//下一页的页码

private int previousPage = 0;//上一页的页码

然后这些属性之间是有联系的，我们可以在构造函数的时候就初始化一些属性
有两种方法：
一，根据总的页数，（假设当前页为1）
public PageBean(int totalRows){
  this.totalRows = totalRows;
  this.currentPage = 1;
  hasPreviousPage = false;
  if ((totalRows % pageRecorders) == 0) {
   totalPages = totalRows / pageRecorders;
  } else {
   totalPages = totalRows / pageRecorders + 1;
  }
  if (totalRows >= pageRecorders) {
   hasNextPage = true;
   nextPage = 2;
   this.pageEndRow = pageRecorders;
  } else {
   this.pageEndRow = totalRows;
   hasNextPage = false;
   nextPage = 1;
  }
   this.pageStartRow = 0;
   previousPage = 1;
}
然后在按下一页或者上一页的时候需要如下函数处理：
public void nextPage() {
  if(hasNextPage == true)
  currentPage = currentPage + 1;
  if ((currentPage - 1) > 0) {
   hasPreviousPage = true;
  } else {
   hasPreviousPage = false;
  }
  if (currentPage >= totalPages) {
   hasNextPage = false;
   this.nextPage = currentPage;
  } else {
   hasNextPage = true;
   nextPage = currentPage+1;
  }
  this.pageStartRow = (currentPage -1) * pageRecorders;
  if(hasNextPage == true)
  this.pageEndRow = pageStartRow + 5;
  else{
   this.pageEndRow =this.totalPages;
  }
  previousPage = currentPage - 1;
}

public void previousPage() {
  if(hasPreviousPage == true)
  currentPage = currentPage - 1;
  if (currentPage == 0) {
   currentPage = 1;
  }
  if (currentPage >= totalPages) {
   hasNextPage = false;
  } else {
   hasNextPage = true;
  }
  nextPage = currentPage + 1;
  if ((currentPage - 1) > 0) {
   hasPreviousPage = true;
   previousPage = currentPage - 1;
  } else {
   hasPreviousPage = false;
   previousPage = currentPage;
  }

  this.pageStartRow = (currentPage -1) * pageRecorders;
  if(hasNextPage == true)
  this.pageEndRow = pageStartRow + 5;
  else{
   this.pageEndRow =this.totalPages;
  }
}
在HTML中按下一页或者上一页的时候有如下代码：
<logic:equal name="page" property="hasNextPage" value="true">
<html:link page="/List.do?action=nextPage">
nextPage
</html:link>
</logic:equal>
<logic:equal name="page" property="hasPreviousPage" value="true">
<html:link page="/List.do?action=previousPage">
PreviousPage
</html:link>
</logic:equal>
然后在Action中作如下处理：
  String currentPage = request.getParameter("currentPage");
  HttpSession session = request.getSession();
  EmployeeForm employeeForm = (EmployeeForm) form;
  String queryString = null;
  String queryCon = null;
  String action = employeeForm.getAction();
  List list = new ArrayList();
  PageBean pb = null;
  EmployeeDao employeeDao = new EmployeeDao();
  if(action == null || action.equals("null")){
   int totalRows = employeeDao.getTotalRows();

    pb = new PageBean(totalRows);
    session.removeAttribute("page");
    queryString = employeeForm.getQueryString();
    queryCon = employeeForm.getQueryCon();
    session.setAttribute("queryString",queryString);
    session.setAttribute("queryCon",queryCon);
    list = employeeDao.getAllEmployee(queryString, queryCon,
      String.valueOf(pb.getPageStartRow()),
      String.valueOf(pb.getPageRecorders()));

  }else if(action.equals("nextPage")){
   queryString = (String)session.getAttribute("queryString");
   queryCon = (String)session.getAttribute("queryCon");
   employeeForm.setQueryString(queryString);
   employeeForm.setQueryCon(queryCon);
   pb = (PageBean)session.getAttribute("page");
   pb.nextPage();
   list = employeeDao.getAllEmployee(queryString, queryCon,
     String.valueOf(pb.getPageStartRow()),
     String.valueOf(pb.getPageRecorders()));
  }else if(action.equals("previousPage")){
   queryString = (String)session.getAttribute("queryString");
   queryCon = (String)session.getAttribute("queryCon");
   employeeForm.setQueryString(queryString);
   employeeForm.setQueryCon(queryCon);
   pb = (PageBean)session.getAttribute("page");
   pb.previousPage();
   list = employeeDao.getAllEmployee(queryString, queryCon,
     String.valueOf(pb.getPageStartRow()),
     String.valueOf(pb.getPageRecorders()));
  }

        pb.description();
        session.setAttribute("page",pb);
  request.setAttribute("admin", "admin");
  request.setAttribute("employee", list);
  return mapping.findForward("showlist");
  然后在数据库查询中有如下代码：
/**
*查询总记录数
*/
public int getTotalRows() {
  int totalRows = 0;
  String sql = "select count(*) from employee";//假设是员工表
  Database db = new Database();
  ResultSet rs = db.executeQuery(sql);
  try {
   while (rs.next()) {
    String id = (String) rs.getString(1);
    totalRows = Integer.parseInt(id);
   }
  } catch (SQLException e) {
   e.printStackTrace();
  }
  db.close();
  return totalRows;
}

/*
*查询每一页需要查询的页码
*/
public List getAllEmployee(String queryString, String queryCon,String startRow,String num) {
  List list = new ArrayList();
  String sql = null;
  if (queryString == null || queryString.equals("")) {
   sql = "select * from employee,dept " +
     "where dept.Id = employee.deptId " +
     "order by employee.id asc"+ " limit "+startRow+","+num;
  } else {
   sql = "select * from employee,dept " +
     "where dept.Id = employee.deptId order by employee."
     + queryString + " " + queryCon + " limit "+startRow+","+num;
  }
  Employee employee = null;
  Database db = new Database();
  ResultSet rs = db.executeQuery(sql);
  try {
   while (rs.next()) {
    String id = (String) rs.getString("employee.id");
    String name = (String) rs.getString("employee.name");
    String deptId = (String) rs.getString("employee.deptId");
    String deptName = (String) rs.getString("dept.deptName");
    employee = new Employee();
    employee.setId(id);
    employee.setName(name);
    employee.setDeptId(deptId);
    employee.setDeptName(deptName);
    list.add(employee);
   }
  } catch (SQLException e) {
   e.printStackTrace();
  }
  db.close();
  return list;
}
这里我用了hibernate进行数据库操作，你也可以用jdbc进行操作，情况类似。

二，根据总的页数，当前页
这样的话构造函数应该写成:
public PageBean(int totalRows,int currentPage) {
  this.totalRows = totalRows;
  this.currentPage = currentPage;
  if(currentPage < 2)
   hasPreviousPage = false;
  else
   hasPreviousPage = true;
  if ((totalRows % pageRecorders) == 0) {
   totalPages = totalRows / pageRecorders;
  } else {
   totalPages = totalRows / pageRecorders + 1;
  }
  if (currentPage < totalPages) {
   hasNextPage = true;
   nextPage = currentPage + 1;
   pageStartRow = (currentPage - 1)*pageRecorders;
   this.pageEndRow = pageStartRow + pageRecorders;
  } else if(currentPage == totalPages){
   pageStartRow = (currentPage - 1)*pageRecorders;
   this.pageEndRow = totalRows;
   hasNextPage = false;
   nextPage = currentPage;
  }
  if(currentPage < 2){
   previousPage = currentPage;
   hasPreviousPage = false;
  }else if(currentPage > 1){
   previousPage = currentPage-1;
   hasPreviousPage = true;
  }
}

在action中应该写成
if(currentPage == null){
    pb = new PageBean(totalRows);
    session.removeAttribute("page");
    queryString = employeeForm.getQueryString();
    queryCon = employeeForm.getQueryCon();
    session.setAttribute("queryString",queryString);
    session.setAttribute("queryCon",queryCon);
    list = employeeDao.getAllEmployee(queryString, queryCon,
      String.valueOf(pb.getPageStartRow()),
      String.valueOf(pb.getPageRecorders()));
    }
   else{
    pb = new PageBean(totalRows,Integer.parseInt(currentPage));
    queryString = employeeForm.getQueryString();
    queryCon = employeeForm.getQueryCon();
    session.setAttribute("queryString",queryString);
    session.setAttribute("queryCon",queryCon);
    list = employeeDao.getAllEmployee(queryString, queryCon,
      String.valueOf(pb.getPageStartRow()),
      String.valueOf(pb.getPageRecorders()));
   }
  session.setAttribute("page",pb);
  request.setAttribute("admin", "admin");
  request.setAttribute("employee", list);
  return mapping.findForward("showlist");

在jsp中应该写成：
<logic:equal name="page" property="hasNextPage" value="true">
<a href="List.do?currentPage=<bean:write name="page" property="nextPage"/>">
nextPage
</a>
</logic:equal>
<logic:equal name="page" property="hasPreviousPage" value="true">
|
<a href="/test/List.do?currentPage=<bean:write name="page" property="previousPage"/>">
PreviousPage
</a>
</logic:equal>
数据库查询部分依然适用。

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评论人：ffyahoo	发表时间: Sat Nov 11 15:17:35 CST 2006
不是吧，我刚写好，你就拿来抄了。。。

评论人：ffyahoo	发表时间: Mon Nov 13 09:48:19 CST 2006
别人的东东,你总该在上面注明出处吧...

评论人：mrou2001	发表时间: Thu Dec 07 14:21:59 CST 2006
加油啊，支持

评论人：kete2003	发表时间: Sun Dec 24 17:04:08 CST 2006
初来，上周刚好也写了一个分页，虽然没有完成，但也算小成吧，感觉楼主在构造分页时确也花了很多的功力。感谢中----！不过，本人觉得有点不妥的就是在传入方法参数时为何不用VO进行数据的封装，看起来可能会更简明一些。

评论人：liqwei	发表时间: Mon Dec 25 14:42:23 CST 2006
太乱了，定义好多没有的变量： pageEndRows = pageStartRows + pageRecorders; hasNextPage = (totalPages+1>currentPage); hasPreviousPage = (currentPage>1); 而且实体的数据对象和分页信息，是分开的，为什么不合并在一起，这样不是更简介吗？

评论人：devejonson	发表时间: Tue Jan 23 17:41:48 CST 2007
为什么不把当前页也封装到form里呢？个人觉得比较复杂了点，楼主可以看下hiberate自己的打出来的sql，根据这个sql可以有一个比较简单和清晰的思路。

评论人：wangjfc	发表时间: Wed Mar 07 23:03:11 CST 2007
怎么发表不了啊言论自由啊

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