- 技术人生
- Hibernate+Struts分页代码
关于分页显示方面的文章，网上搜索会有好几大箩，当然每个人都有自己的思路和出发点。我的基本思路也很简单，就是将搜索过程分为两个部分：“预搜索”和“分页显示”。预搜索负责查询记录主键ID集，并且在整个查询分页过程中只执行一次；分页显示负责从预搜索的主键ID集中找出当前要显示的记录，每进行一次翻页操作便执行一次，从而实现分页显示功能。由于查询的Where条件为主键ID，并且每次只查询当页显示的记录数（比如：20条），所以在重量级查询中有着一定的性能优势。本文主要从以下三个方面（三篇文章）来进行讲解：1. 构建生成分页变量实体、存储查询结果实体2. 预搜索类、分页搜索类、HibernateUtil工具类部分关联代码3. 实现预搜索、分页搜索的两个类及用Struts的Action调用分页实例注：View视图层的JSP代码未贴出来，相信大家在得到Result后都知道如何用Struts标签显示首先我们为查询分页构建三个基础类：Page（保存分页的当前状态值）、PageUtil（生成Page）、Result（保存查询结果），代码都有详细的文档解释，就不再另作说明了，这三个类的代码分别如下：/**********************************Page类*********************************************/package com.nyhr.struts.page;/** * 分页实体类，保存当前分页状态变量 * @author Yeno.hhr*/public class Page { /** imply if the page has previous page */ private boolean hasPrePage; /** imply if the page has next page */ private boolean hasNextPage; /** the number of every page */ private int everyPage; /** the total page number */ private int totalPage; /** the total record number */ private int totalRecords; /** the number of current page */ private int currentPage; /** the begin index of the records by the current query */ private int beginIndex; /** The default constructor */ public Page(){ } /** construct the page by everyPage * @param everyPage * */ public Page(int everyPage){ this.everyPage = everyPage; } /** The whole constructor */ public Page(boolean hasPrePage, boolean hasNextPage, int everyPage, int totalPage, int totalRecords, int currentPage, int beginIndex) { this.hasPrePage = hasPrePage; this.hasNextPage = hasNextPage; this.everyPage = everyPage; this.totalPage = totalPage; this.totalRecords = totalRecords; this.currentPage = currentPage; this.beginIndex = beginIndex; } /** * @return * Returns the beginIndex. */ public int getBeginIndex() { return beginIndex; } /** * @param beginIndex * The beginIndex to set. */ public void setBeginIndex(int beginIndex) { this.beginIndex = beginIndex; } /** * @return * Returns the currentPage. */ public int getCurrentPage() { return currentPage; } /** * @param currentPage * The currentPage to set. */ public void setCurrentPage(int currentPage) { this.currentPage = currentPage; } /** * @return * Returns the everyPage. */ public int getEveryPage() { return everyPage; } /** * @param everyPage * The everyPage to set. */ public void setEveryPage(int everyPage) { this.everyPage = everyPage; } /** * @return * Returns the hasNextPage. */ public boolean getHasNextPage() { return hasNextPage; } /** * @param hasNextPage * The hasNextPage to set. */ public void setHasNextPage(boolean hasNextPage) { this.hasNextPage = hasNextPage; } /** * @return * Returns the hasPrePage. */ public boolean getHasPrePage() { return hasPrePage; } /** * @param hasPrePage * The hasPrePage to set. */ public void setHasPrePage(boolean hasPrePage) { this.hasPrePage = hasPrePage; } /** * @return Returns the totalPage. * */ public int getTotalPage() { return totalPage; } /** * @param totalPage * The totalPage to set. */ public void setTotalPage(int totalPage) { this.totalPage = totalPage; } /** * @param totalRecords * The totalRecords to set. */ public void settotalRecords(int totalRecords) { this.totalRecords = totalRecords; } /** * @return Returns the totalRecords. * */ public int getTotalRecords() { return this.totalRecords; }}/**********************************PageUtil类*********************************************/package com.nyhr.struts.page;/** * 分页工具类，初始化Page对象 * @author Yeno.hhr*/public class PageUtil { /** * Use the origin page to create a new page * @param page * @param totalRecords * @return */ public static Page createPage(Page page, int totalRecords){ return createPage(page.getEveryPage(), page.getCurrentPage(), totalRecords); } /** * the basic page utils not including exception handler * @param everyPage * @param currentPage * @param totalRecords * @return page */ public static Page createPage(int everyPage, int currentPage, int totalRecords){ everyPage = getEveryPage(everyPage); currentPage = getCurrentPage(currentPage); int beginIndex = getBeginIndex(everyPage, currentPage); int totalPage = getTotalPage(everyPage, totalRecords); boolean hasNextPage = hasNextPage(currentPage, totalPage); boolean hasPrePage = hasPrePage(currentPage); return new Page(hasPrePage, hasNextPage, everyPage, totalPage, totalRecords, currentPage, beginIndex); } private static int getEveryPage(int everyPage){ return everyPage == 0 ? 10 : everyPage; } private static int getCurrentPage(int currentPage){ return currentPage == 0 ? 1 : currentPage; } private static int getBeginIndex(int everyPage, int currentPage){ return (currentPage - 1) * everyPage; } private static int getTotalPage(int everyPage, int totalRecords){ int totalPage = 0; if(totalRecords % everyPage == 0) totalPage = totalRecords / everyPage; else totalPage = totalRecords / everyPage + 1 ; return totalPage; } private static boolean hasPrePage(int currentPage){ return currentPage == 1 ? false : true; } private static boolean hasNextPage(int currentPage, int totalPage){ return currentPage == totalPage || totalPage == 0 ? false : true; } } /**********************************Result类*********************************************/package com.nyhr.struts.page;import java.util.List;/** * <p>Title: 检索结果集实体类</p> * <p>Description: 保存分页参数及数据库查询的结果,用于页面显示</p> * <p>Copyright: Copyright (c) 2006</p> * <p>Company: 四方人才网</p> * @author Yeno.hhr * @version 1.0 */public class Result { /**分页状态变量实体*/ private Page page; /**数据库检索到的当前页结果集*/ private List content; /** * The default constructor */ public Result() { super(); } /** * The constructor using fields * * @param page * @param content */ public Result(Page page, List content) { this.page = page; this.content = content; } /** * @return Returns the content. */ public List getContent() { return content; } /** * @return Returns the page. */ public Page getPage() { return page; } /** * The content to set. * @param content */ public void setContent(List content) { this.content = content; } /** * The page to set. * @param page */ public void setPage(Page page) { this.page = page; }} 现在展示在大家面前的是查询分页两个核心类 ：AbstractSearch（预查询初始化程序）、AbstractList（分页及初始化分页程序），代码如下：/********************************AbstractSearch类************************************/package com.nyhr.struts.frame;import java.util.List;import com.nyhr.struts.beans.HibernateUtil;/** * <p>Title: 预查询初始化程序</p> * <p>Description: 所有的初始化查询必须继承此类，本类只负责预查询ID集和Page对象的初始化，不实现显示逻辑</p> * <p>Copyright: Copyright (c) 2006</p> * <p>Company: 四方人才网</p> * @author Yeno.hhr * @version 1.0 */public abstract class AbstractSearch { public AbstractSearch() { super(); } /** * 根据HQL查询出记录的主键ID（主索引）集合 * 注：此hql必须是只检索主键及复合主键的查询语句，具体见应用实例 * @param hql 不带查询的查询语句 * @return idArray 主索引集合（可以主键ID，也可以是复合ID） */ public Object[] getIDList(String hql) { List list = HibernateUtil.query(hql); if (list==null || list.size()==0) return null; return list.toArray(); } /** * 根据HQL查询出记录的主键ID（主索引）集合 * 注：此hql必须是只检索主键及复合主键的查询语句，具体见应用实例 * @param hql 带参数的查询语句 * @param bean 参数设置实体类 * @return Object[] 主索引集合（可以主键ID，也可以是复合ID） */ public Object[] getIDList(String hql, Object bean) { List list = HibernateUtil.query(hql,bean); if (list==null || list.size()==0) return null; return list.toArray(); } /**子类方法：根据子类的需要选择调用AbstractSearch的“带参”和“不带参”两种查询中的一种返回主键ID的数组集*/ abstract public Object[] getList(); /**子类方法：设定查询条件*/ abstract protected void condition();}/********************************AbstractList类************************************/package com.nyhr.struts.frame;import com.nyhr.struts.page.*;import com.nyhr.struts.constant.SysConstant;import com.nyhr.struts.hibernate.HibernateSessionFactory;import org.hibernate.HibernateException;import org.hibernate.Query; import org.hibernate.Session;import java.util.List;import java.util.ArrayList;/** * <p>Title: 分页及初始化分页程序</p> * <p>Description: 所有的初始化分页必须继承此类，如果是预查询调用，同时会初始化Page实体，否则Page实体会由FormBean提交生成</p> * <p>Copyright: Copyright (c) 2006</p> * <p>Company: 四方人才网</p> * @author Yeno.hhr * @version 1.0 */abstract public class AbstractList { private Page page; /**查询结果的主键ID集*/ private Object[] idList; public AbstractList(){} /** * 预查询初始化分页构造（初次查询） * @param hql 查询语句 * @param search 预查询类 */ public AbstractList(AbstractSearch search){ this.idList=search.getList(); } /** * 查询分页构造（分页查询） * @param page 分页状态实体 * @param idList */ public AbstractList(Page page, Object[] idList){ this.idList=idList; this.page=page; }
/**子类方法：设置分页查询的查询语句*/ abstract protected String getHql(); /** * 返回查询结果 * @return Result */ public Result getResult(){ if(page==null){ if(idList==null) this.page = PageUtil.createPage(SysConstant.PAGE_SIZE,1,0); else this.page = PageUtil.createPage(SysConstant.PAGE_SIZE,1,idList.length); } return new Result(page, getListByPage()); } /** * 分页查询，返回当前页的查询结果集 * @param hql * @return list 结果集 */ public List getListByPage(){ List list = null; if (page.getTotalPage() < 1) return list; try{ String hql=getHql(); if(hql==null || hql.equals("")) return list; Object[] bean=getCurrentIds(); if(bean!=null) list=HibernateUtil.query(hql,bean); else list=HibernateUtil.query(hql); }catch(Exception e){ System.out.println(e.getMessage()); throw new RuntimeException(e); } return list; }
/** * 从查询结果的ID集中找出当前页的ID集 * @param arr 所有查询结果的主键ID集 * @return Object[] */ private Object[] getCurrentIds(){ if(idList==null) return null; ArrayList<Object> list = new ArrayList<Object>(); int begin = page.getBeginIndex(); int ends = page.getTotalRecords(); int end = begin+page.getEveryPage(); if (end >= ends) end = ends; for (int l=begin;l<end;l++){ list.add(idList[l]); } return list.toArray(); } /** * 返回查询结果主键ID集的字符串组合形式 * @return String */ public String getIdList(){ String ids=""; if(idList == null) return ids; for(int x=0; x<idList.length; x++){ ids+=idList[x].toString(); if(x<idList.length-1) ids+=","; } return ids; }}/********************************HibernateUtil类************************************/public class HibernateUtil { private HibernateUtil(){} /** * 执行数据库查询,返回结果集List * @param hsql HSQL查询语句 * @return list 结果集 */ public static List query(String hql) { List list = null; Query query = null; Session sess = HibernateSessionFactory.currentSession(); try{ //创建一条HQL查询语句 if (hql.toLowerCase().contains("from ")) query = sess.createQuery(hql); else query = sess.getNamedQuery(hql); list = query.list(); }catch(HibernateException e) { System.out.println("Hibernate Exception:@"+e.getMessage()); throw new RuntimeException(e); }finally { HibernateSessionFactory.closeSession(); } return list; } public static List query(String hql, Object bean){ List list = null; Query query = null; Session sess = HibernateSessionFactory.currentSession(); try { //创建一条HQL查询语句 if (hql.toLowerCase().contains("from ")) query = sess.createQuery(hql); else query = sess.getNamedQuery(hql); query.setProperties(bean); list = query.list(); }catch(HibernateException e) { System.out.println("Hibernate Exception:@"+e.getMessage()); throw new RuntimeException(e); } finally { HibernateSessionFactory.closeSession(); } return list; }}
