Pager-taglib在项目中的使用

     在上篇文章Pager-taglib分页 对其有了一个基本的了解,接下来我们将会对pager-taglib如何在项目中使用进行一个比较详细的说明.

 

1建立LocalThread类,对分页的常数进行封装

     代码如下

package com.tgb.oa;/** *  *    采用ThreadLocal来存储分页变量. * @author   jnqqls * @group    TGB * @version  1.0 * @comments */public class SystemContext {private static ThreadLocal offset = new ThreadLocal();private static ThreadLocal pagesize = new ThreadLocal();/** * 从线程中获取offset字段 * @return */public static int getOffset(){Integer os = (Integer)offset.get();if(os == null){return 0;}return os;}public static void setOffset(int offsetvalue){offset.set(offsetvalue);}public static void removeOffset(){offset.remove();}public static int getPagesize(){Integer ps = (Integer)pagesize.get();if(ps == null){return Integer.MAX_VALUE;}return ps;}public static void setPagesize(int pagesizevalue){pagesize.set(pagesizevalue);}public static void removePagesize(){pagesize.remove();}}

 

 

2建立PagerFilter过滤器,将参数读取到ThreadLocal中.

     代码如下:

package com.tgb.oa.web;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 com.tgb.oa.SystemContext;/** *  * @oa_02    过滤器,获取相关分页数据. * @author   jnqqls * @group    TGB * @version  1.0  * @comments */public class PagerFilter implements Filter {public void destroy() {}public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {HttpServletRequest httpRequest = (HttpServletRequest)request;SystemContext.setOffset(getOffset(httpRequest)); SystemContext.setPagesize(getPagesize(httpRequest));try{chain.doFilter(request, response);}finally{//清空ThreadLocal中的值,避免类的溢出.SystemContext.removeOffset();SystemContext.removePagesize();}}protected int getOffset(HttpServletRequest request){int offset = 0;try {offset = Integer.parseInt(request.getParameter("pager.offset"));} catch (NumberFormatException ignore) {}return offset;}protected int getPagesize(HttpServletRequest request){return 10;}public void init(FilterConfig arg0) throws ServletException {}}

 

3配置filter在WEB.XML文件中

代码如下:

<!-- 定义分页Filter -->  <filter>      <filter-name>PagerFilter</filter-name>      <filter-class>com.tgb.oa.web.PagerFilter</filter-class>  </filter>    <filter-mapping>      <filter-name>PagerFilter</filter-name>      <url-pattern>/*</url-pattern>  </filter-mapping>

 

 

4建立抽象类,将分页功能抽象成一个方案,可以在更多的场合下进行运用.

     代码如下:

package com.tgb.oa.manager.impl;import java.util.List;import org.hibernate.Query;import org.springframework.orm.hibernate3.support.HibernateDaoSupport;import com.tgb.oa.PagerModel;import com.tgb.oa.SystemContext;import com.tgb.oa.manager.SystemException;/** *  *     抽象分页查询. * @author   jnqqls * @group    TGB * @version  1.0  * @comments */public class AbstractManager extends HibernateDaoSupport {public PagerModel searchPaginated(String hql){return searchPaginated(hql,null,SystemContext.getOffset(),SystemContext.getPagesize());}public PagerModel searchPaginated(String hql,Object param){return searchPaginated(hql,new Object[]{param},SystemContext.getOffset(),SystemContext.getPagesize());}public PagerModel searchPaginated(String hql,Object[] params){return searchPaginated(hql,params,SystemContext.getOffset(),SystemContext.getPagesize());}/** * 没有参数 * @param hql * @param offset * @param pagesize * @return */public PagerModel searchPaginated(String hql,int offset,int pagesize){return searchPaginated(hql,null,offset,pagesize);}/** * 只有一个参数 * @param hql * @param obj * @param offset * @param pagesize * @return */public PagerModel searchPaginated(String hql,Object obj,int offset,int pagesize){return searchPaginated(hql,new Object[]{obj},offset,pagesize);}/** * 根据hql语句进行分页查询 * @param hql * @param params  HQL语句带的多个参数值. * @param offset  从第几条记录开始查询 * @param pagesize 总共要显示的页数. * @return */public PagerModel searchPaginated(String hql,Object[] params,int offset,int pagesize){//第一步:获取总记录数.//获取总数的查询语句String countHql=getCountQuery(hql);//创建查询对象.Query query =getSession().createQuery(countHql);//通过循环将参数设置到语句中.if(params != null && params.length>0){for(int i=0;i<params.length;i++){query.setParameter(i, params[i]);}}//获取总的记录数int total = ((Long)query.uniqueResult()).intValue();//获取当前的结果集query = getSession().createQuery(hql);if(params != null && params.length>0){for(int i=0;i<params.length;i++){query.setParameter(i, params[i]);}}//设置参数query.setFirstResult(offset);query.setMaxResults(pagesize);//获取结果集.List datas=query.list();//创建PagerModel对象.PagerModel pm = new PagerModel();pm.setDatas(datas);pm.setTotal(total);return pm;}/** * 根据HQL语句,获得查找总记录数的HQL语句. * @param hql * @return */private String getCountQuery(String hql) {//根据from字截取查询语句.int index = hql.indexOf("from");if(index != -1){return "select count(*) " + hql.substring(index);}throw new SystemException("无效的HQL查询语句！");}}

5实现抽象类,完成方法的调用.

代码如下:

package com.tgb.oa.manager.impl;import java.util.List;import org.springframework.orm.hibernate3.support.HibernateDaoSupport;import com.tgb.oa.PagerModel;import com.tgb.oa.manager.OrgManager;import com.tgb.oa.model.Orgnization;/** *  * @ 实现组织机构管理接口 * @author jnqqls * @group TGB * @version 1.0  * @comments */public class OrgManagerImpl extends AbstractManager implements OrgManager {@Overridepublic PagerModel findOrgs(int parentId) {//如果parentId＝0，则查找顶级机构列表if(parentId == 0){return searchPaginated("from Orgnization o where o.parent is null");}return searchPaginated("from Orgnization o where o.parent.id = ?", parentId);}}

 

   剩下的就是相关的 Action进行调用,配置jsp页面.以上便是pager-taglib在项目中后台的相关使用.

 

总结:pager-taglib是分页的一个好工具，经过简单的配置可以轻松实现分页功能,我们所需要学习的是它本身所具有封装思想.