在做分页的时候，出现java.lang.NumberFormatException: null 错误

分页的util类：

package com.sy.util;

import java.util.List;
@SuppressWarnings("unchecked")
public class PageBean {

    private int pageSize;
    private int totalPage;
    private int rowCount;
    private int currentPage;
    private int prePage;
    private int nextPage;
    private boolean hasNextPage;
    private boolean hasPreviousPage;
    private List list;

    public PageBean() {
        this.pageSize=10;
    }

    public int getPageSize() {
        return pageSize;
    }

    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }

    public int getTotalPage() {
        return totalPage;
    }

    public void setTotalPage(int totalPage) {
        this.totalPage = totalPage;
    }

    public int getRowCount() {
        return rowCount;
    }

    public void setRowCount(int rowCount) {
        this.rowCount = rowCount;
    }

    public int getCurrentPage() {
        return currentPage;
    }

    public void setCurrentPage(int currentPage) {
        this.currentPage = currentPage;
    }

    public int getPrePage() {
        return prePage;
    }

    public void setPrePage(int prePage) {
        this.prePage = prePage;
    }

    public int getNextPage() {
        return nextPage;
    }

    public void setNextPage(int nextPage) {
        this.nextPage = nextPage;
    }

    public boolean isHasNextPage() {
        return hasNextPage;
    }

    public void setHasNextPage(boolean hasNextPage) {
        this.hasNextPage = hasNextPage;
    }

    public boolean isHasPreviousPage() {
        return hasPreviousPage;
    }

    public void setHasPreviousPage(boolean hasPreviousPage) {
        this.hasPreviousPage = hasPreviousPage;
    }

    public List getList() {
        return list;
    }

    public void setList(List list) {
        this.list = list;
    }


}

分页的数据库操作和逻辑判断我把他单独用一个PageDaoImpl来实现：
   public class PageDaoImpl extends HibernateDaoSupport {

    private String hql;
    public PageBean page;
    public int start;

    public void init(int start){
       page = new PageBean();
      this.hql = "from ProAddTask";
       this.start = start;
       setRowCount();
       setTotalPage();
       setCurrentPage();
       setPrePage();
       setNextPage();
       setPreOrNextBoolean();
    }

    public int getRowCount(){
      return this.getHibernateTemplate().find("select p from ProAddTask p").size();
    }

    public PageBean getPage(){
       List list = (List)getHibernateTemplate().execute(new HibernateCallback(){
        public Object doInHibernate(Session session) throws HibernateException, SQLException {
         Query query = session.createQuery(hql);
         query.setFirstResult(getStartIndex());
         query.setMaxResults(page.getPageSize());
         return query.list();
        }
       });
       page.setList(list);
       return page;
    }

    public void setPreOrNextBoolean() {
        if (page.getCurrentPage() <= 1) {
            page.setHasPreviousPage(false);
        } else {
            page.setHasPreviousPage(true);
        }
        if (page.getCurrentPage() >= page.getTotalPage()) {
            page.setHasNextPage(false);
        } else {
            page.setHasNextPage(true);
        }
    }

    public void setCurrentPage() {
        if (start < 1) {
            page.setCurrentPage(1);
        }
        if (start > page.getTotalPage()) {
            page.setCurrentPage(page.getTotalPage());
        }
        page.setCurrentPage(start);
    }

    public void setPrePage() {
        page.setPrePage(page.getCurrentPage() - 1);
    }

    public void setNextPage() {
        page.setNextPage(page.getCurrentPage() + 1);
    }

    public void setTotalPage() {
        int rowCount = getRowCount();
        int pageSize = page.getPageSize();
        if (rowCount > pageSize) {
            if (rowCount % pageSize == 0) {
                page.setTotalPage(rowCount / pageSize);
            } else {
                page.setTotalPage(1 + (rowCount / pageSize));
            }
        } else {
            page.setTotalPage(1);
        }
    }

    public void setRowCount() {
        page.setRowCount(getRowCount());
    }

    public int getStartIndex() {
        int startIndex = 0;
        if (start < 0) {
            startIndex = 0;
        } else {
            if (start > page.getTotalPage()) {
                startIndex = page.getPageSize() * (page.getTotalPage() - 1);
            } else {
                startIndex = page.getPageSize() * (start - 1);
            }
        }
        return startIndex;
    }
}



然后是业务层接口，举例AdminService.java

//管理员service层接口
public interface AdminService extends BaseService{
//分页初始化
    public void init(int pno);
//分页实现
    public Page getPage();
}

实现类AdminServiceImpl.java   //管理员service层实现类
public class AdminServiceImpl extends BaseServiceImpl implements AdminService {

    public Page getPage() {
        return Pdao.getPage();
    }
    public void init(int pno) {
        Pdao.init(pno);
    }
}


struts的action层AdminAction.java



//管理员action实现类
public class AdminAction extends BaseAction {
  private QueryTaskService queryTaskService;public QueryTaskService getQueryTaskService() {
return queryTaskService;
} public void setQueryTaskService(QueryTaskService queryTaskService) {
this.queryTaskService = queryTaskService;
}

//查看管理员
    public ActionForward listAdmins(ActionMapping mapping, ActionForm form,
            HttpServletRequest request, HttpServletResponse response) {

           System.out.println(request.getParameter("pno"));
           int pno = (new Integer(request.getParameter("pno"))).intValue();
           queryTaskService.init(pno);
           Page myPage = queryTaskService.getPage();
           List myList = queryTaskService.getPage().getList();
           request.setAttribute("myPage", myPage);
           request.setAttribute("AdminList", myList);
           return mapping.findForward("show");

    }
}


结构清晰，也很实用。

页面lookAdmin.jsp



<%@ page language="java" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean" %>
<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html" %>
<%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic" %>
<%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles" %>
<html>
    <head>
        <meta http-equiv="Content-Language" content="zh-cn">
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
        <title></title>
    </head>
    <body>
    <table align="center" width="500">
    <tr>
       <td align="center" colspan="10">
          <logic:present name="myPage">
            <html:link page="/AdminPage.do?pno=1">首页</html:link>
          <logic:equal name="myPage" property="hasPreviousPage" value="false">上一页</logic:equal>
          <logic:equal name="myPage" property="hasPreviousPage" value="true">
           <a href="./AdminPage.do?pno=<bean:write name="myPage" property="prePage"/>">上一页</a>
      </logic:equal>

           每页<bean:write name="myPage" property="pageSize"/>条记录
           共<bean:write name="myPage" property="rowCount"/>条记录
                当前第(<bean:write name="myPage" property="currentPage"/>/<bean:write name="myPage" property="totalPage"/>)页
        <logic:equal name="myPage" property="hasNextPage" value="false">下一页</logic:equal>
        <logic:equal name="myPage" property="hasNextPage" value="true">
         <a href="./AdminPage.do?pno=<bean:write name="myPage" property="nextPage"/>">下一页</a>
        </logic:equal>
           <a href="./AdminPage.do?pno=<bean:write name='myPage' property='totalPage'/>">末页</a>
        </logic:present>
      </td>
      </tr>
    </table>
    </body>
</html>  System.out.println(request.getParameter("pno"));
打印出来是null
~~

解决方案 »

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lz把这个request.getParameter("pno")改成request.getParameter("myPage")
把页数打印出来看看就知道了，是否为合法number
分页时参数是String,要强转Int!
你传递的index肯定有问题的 debug一下具体看看
晕~问题解决了~~
pno=new Integer(request.getParameter("pno")).intValue();
要给个if判断是否为null~·if (request.getParameter("pno")==null) {
             pno=1;
         } else {
         pno=new Integer(request.getParameter("pno")).intValue();
         }