Hibernate+Struts分页代码(zhuan)

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;
    }
}