利用组件分页

. 如何分页?
    1.把pager-taglib.jar放到lib目录下(仅此足亦，完全没必要改web.xml什么的，还有官方war包中的东西都可以不要)
    2.在Jsp页面嵌入<%@ taglib uri="http://jsptags.com/tags/navigation/pager" prefix="pg" %> 


分页代码:
action中示范代码:

PageModel pm = empMgr.selectAllEmp(PageModel.getOffset(request), PageModel.getPageSize(request)) ;
request.setAttribute("pm", pm) ;		
		
jsp示范代码:
........
........
//分页代码
<pg:pager url="employee.do" items="${pm.total}" maxPageItems = "5" maxIndexPages="10" export="currentPageNumber=pageNumber" >
<pg:param  name="pageSize" value="5" />
<pg:first>
	<a href="${pageUrl}">首页</a>
</pg:first>
<pg:prev>
	<a href="${pageUrl}">上一页</a>
</pg:prev>
<pg:pages>  
        <c:choose>  
            <c:when test="${currentPageNumber eq pageNumber}">  
                <font color="red">${pageNumber }</font>  
            </c:when>  
            <c:otherwise>  
                <a href="${pageUrl}">${pageNumber }</a>  
            </c:otherwise>  
        </c:choose>  
    </pg:pages> 
<pg:next>
	<a href="${pageUrl}">下一页</a>
</pg:next>
<pg:last>
	<a href="${pageUrl}">尾页</a>
</pg:last>

</pg:pager> 

/*************PageModule类的代码**************/

public class PageModel {
	
	private List datas; //页面上要显示的数据
	private int total;  //总的条数，作用：总共有多少页
	
	public List getDatas() {
		return datas;
	}
	public void setDatas(List datas) {
		this.datas = datas;
	}
	public int getTotal() {
		return total;
	}
	public void setTotal(int total) {
		this.total = total;
	}
	
	public static int getOffset(HttpServletRequest request) {
		int offset = 0 ;
		String strOffset = request.getParameter("pager.offset") ;
		if (strOffset != null) {
			offset = Integer.parseInt(strOffset) ;
		}
		return offset ;
	}
	
	public static int getPageSize(HttpServletRequest request) {
		int pageSize = 5 ;
		String strPageSize = request.getParameter("pageSize") ;
		if (strPageSize != null) {
			pageSize = Integer.parseInt(strPageSize) ; 
		}
		
		return  pageSize ;
	}
}

/********************************************************************/
/*****************抽象分页*******仅供参考******************************/
/********************************************************************/

package com.oa.manager.impl;

import java.util.List;

import org.hibernate.Query;
import org.springframework.orm.hibernate3.support.HibernateDaoSupport;

import com.oa.PagerModel;

public class AbstractPagerManager extends HibernateDaoSupport {
	
		
	public PagerModel searchPaginated(String hql,int offset, int pagesize) {
		return this.searchPaginated(hql, null, offset, pagesize);
	}
	
	public PagerModel searchPaginated(String hql, Object obj, int offset, int pagesize) {
		return this.searchPaginated(hql, new Object[]{obj}, offset, pagesize);
	}
	
	/**
	 * 根据Hql语言进行分页
	 * @param hql HQL语句
	 * @param params HQL语句的参数
	 * @param offset 从第几条记录开始查询
	 * @param pagesize 每页显示多少条
	 * @return
	 */
	@SuppressWarnings("unchecked")
	public PagerModel searchPaginated(String hql,Object[] params, int offset, int pagesize) {
		
		//获取总记录数
		String countHql = this.getCountQuery(hql);
		System.out.println("countHql: " + countHql);
		Query query = this.getSession().createQuery(countHql);
		if(query != null && params != null && params.length > 0) {
			for(int i=0; i<params.length; i++) {
				query.setParameter(i, params[i]);
			}
		}
		
		int total = ((Long)query.uniqueResult()).intValue();
		
		//获得当前页的结果集
		query = this.getSession().createQuery(hql);
		if(query != null && params != null && params.length > 0) {
			for(int i=0; i<params.length; i++) {
				query.setParameter(i, params[i]);
			}
		}
		query.setFirstResult(offset);
		query.setMaxResults(pagesize);
		List<Organization> list = query.list();
		
		PagerModel pm = new PagerModel();
		pm.setTotal(total);
		pm.setList(list);
		
		return pm;
		
	}
	
	private String getCountQuery(String hql) {
		System.out.println(hql);
		int index = hql.indexOf("from");
		System.out.println("index:" + index);
		if(index != -1){
			return "select count(*) " + hql.substring(index);
		}
		
		System.out.println("问题出了");
		throw new RuntimeException("无效的HQL查询语句！");

		
	}
}