分页实现1

分页的2个重要参数

1.总记录数

2.每页显示结果集

 

设计成PageModel类

public class PageModel { private List datas; private long totalRecords;

 

分页的接口设计

package cn.yjj.oa.base; import java.util.List; import org.hibernate.Query; import org.springframework.orm.hibernate3.support.HibernateDaoSupport; public abstract class AbstracManager extends HibernateDaoSupport { protected PageModel getScrollDatas(String hql){ return this.getScrollDatas(hql, null, SystemContext.getFirstIndex(), SystemContext.getMaxRecords()); } protected PageModel getScrollDatas(String hql, Object param){ return this.getScrollDatas(hql, param, SystemContext.getFirstIndex(), SystemContext.getMaxRecords()); } protected PageModel getScrollDatas(String hql, Object[] params){ return this.getScrollDatas(hql, params, SystemContext.getFirstIndex(), SystemContext.getMaxRecords()); } protected PageModel getScrollDatas(String hql, int firstIndex, int maxResults){ return this.getScrollDatas(hql, null, firstIndex, maxResults); } protected PageModel getScrollDatas(String hql, Object param, int firstIndex, int maxResults){ return this.getScrollDatas(hql, new Object[]{param}, firstIndex, maxResults); } @SuppressWarnings("unchecked") protected PageModel getScrollDatas(String hql, Object[] params, int firstIndex, int maxResults){ String totalHql = getTotalHql(hql); Query query = this.getSession().createQuery(totalHql); if(params!=null && params.length>0){ for (int i = 0; i < params.length; i++) { query.setParameter(i, params[i]); } } long totalRecords = (Long)query.uniqueResult(); query = this.getSession().createQuery(hql); if(params!=null && params.length>0){ for (int i = 0; i < params.length; i++) { query.setParameter(i, params[i]); } } List datas = query.setFirstResult(firstIndex).setMaxResults(maxResults).list(); return new PageModel(datas, totalRecords); } private String getTotalHql(String hql){ int index = hql.indexOf("from"); if(index!=-1){ return "select count(*) "+hql.substring(index); } throw new SystemException("非法的hql查询语句"); } }

 

 使用ThreadLocal设置开始索引和每页最大显示记录数

1.定义ThreadLocal

package cn.yjj.oa.base; public class SystemContext { private static ThreadLocal firstIndex = new ThreadLocal(); private static ThreadLocal maxRecords = new ThreadLocal(); public static void setFirstIndex(int offset){ firstIndex.set(offset); } public static int getFirstIndex(){ Integer offset = (Integer)firstIndex.get(); if(offset<0){ offset = 0; } return offset; } public static void removeFirstIndex(){ firstIndex.remove(); } public static int getMaxRecords() { Integer maxs = (Integer)maxRecords.get(); if(maxs<1){ maxs = Integer.MAX_VALUE; } return maxs; } public static void setMaxRecords(int maxs) { maxRecords.set(maxs); } public static void removeMaxRecords(){ maxRecords.remove(); } }

 

2.使用Filter在每一次请求前设置ThreadLocal

package cn.yjj.oa.web.filter; import java.io.IOException; import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; import javax.servlet.http.HttpServletRequest; import cn.yjj.oa.base.SystemContext; public class SystemContextFilter implements Filter { public void destroy() { // TODO Auto-generated method stub } public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest)req; int firstIndex = 0; try { firstIndex = Integer.parseInt(request.getParameter("pager.offset")); } catch (NumberFormatException e) { } int maxRecords = 5; SystemContext.setFirstIndex(firstIndex); SystemContext.setMaxRecords(maxRecords); try { chain.doFilter(req, resp); } finally{ SystemContext.removeFirstIndex(); SystemContext.removeMaxRecords(); } } public void init(FilterConfig arg0) throws ServletException { // TODO Auto-generated method stub } }

 

3.在业务逻辑层取得ThreadLocal

protected PageModel getScrollDatas(String hql){ return this.getScrollDatas(hql, null, SystemContext.getFirstIndex(), SystemContext.getMaxRecords()); }