偷窥struts+hibernate分页(第二种方法)

应用Hibernate3的DetachedCriteria实现分页查询    

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Hibernate3 提供了DetachedCriteria，使得我们可以在Web层构造detachedCriteria，然后调用业务层Bean，进行动态条件查询，根据这一功能，我设计了通用的抽象Bean基类和分页类支持，代码来自于Quake Wang的javaeye-core包的相应类，然后又做了很多修改。

分页支持类：

java代码:  


package com.iteye.common.util;

import java.util.List;

public class PaginationSupport {

        public final static int PAGESIZE = 30;

        privateint pageSize = PAGESIZE;

        privateList items;

        privateint totalCount;

        privateint[] indexes = newint[0];

        privateint startIndex = 0;

        public PaginationSupport(List items, int totalCount){
                setPageSize(PAGESIZE);
                setTotalCount(totalCount);
                setItems(items);               
                setStartIndex(0);
        }

        public PaginationSupport(List items, int totalCount, int startIndex){
                setPageSize(PAGESIZE);
                setTotalCount(totalCount);
                setItems(items);               
                setStartIndex(startIndex);
        }

        public PaginationSupport(List items, int totalCount, int pageSize, int startIndex){
                setPageSize(pageSize);
                setTotalCount(totalCount);
                setItems(items);
                setStartIndex(startIndex);
        }

        publicList getItems(){
                return items;
        }

        publicvoid setItems(List items){
                this.items = items;
        }

        publicint getPageSize(){
                return pageSize;
        }

        publicvoid setPageSize(int pageSize){
                this.pageSize = pageSize;
        }

        publicint getTotalCount(){
                return totalCount;
        }

        publicvoid setTotalCount(int totalCount){
                if(totalCount > 0){
                        this.totalCount = totalCount;
                        int count = totalCount / pageSize;
                        if(totalCount % pageSize > 0)
                                count++;
                        indexes = newint[count];
                        for(int i = 0; i < count; i++){
                                indexes[i] = pageSize * i;
                        }
                }else{
                        this.totalCount = 0;
                }
        }

        publicint[] getIndexes(){
                return indexes;
        }

        publicvoid setIndexes(int[] indexes){
                this.indexes = indexes;
        }

        publicint getStartIndex(){
                return startIndex;
        }

        publicvoid setStartIndex(int startIndex){
                if(totalCount <= 0)
                        this.startIndex = 0;
                elseif(startIndex >= totalCount)
                        this.startIndex = indexes[indexes.length - 1];
                elseif(startIndex < 0)
                        this.startIndex = 0;
                else{
                        this.startIndex = indexes[startIndex / pageSize];
                }
        }

        publicint getNextIndex(){
                int nextIndex = getStartIndex() + pageSize;
                if(nextIndex >= totalCount)
                        return getStartIndex();
                else
                        return nextIndex;
        }

        publicint getPreviousIndex(){
                int previousIndex = getStartIndex() - pageSize;
                if(previousIndex < 0)
                        return0;
                else
                        return previousIndex;
        }

}



抽象业务类
java代码:  


/**
* Created on 2005-7-12
*/
package com.iteye.common.business;

import java.io.Serializable;
import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.criterion.DetachedCriteria;
import org.hibernate.criterion.Projections;
import org.springframework.orm.hibernate3.HibernateCallback;
import org.springframework.orm.hibernate3.support.HibernateDaoSupport;

import com.iteye.common.util.PaginationSupport;

public abstract class AbstractManager extends HibernateDaoSupport {

        private boolean cacheQueries = false;

        private String queryCacheRegion;

        publicvoid setCacheQueries(boolean cacheQueries){
                this.cacheQueries = cacheQueries;
        }

        publicvoid setQueryCacheRegion(String queryCacheRegion){
                this.queryCacheRegion = queryCacheRegion;
        }

        publicvoid save(finalObject entity){
                getHibernateTemplate().save(entity);
        }

        publicvoid persist(finalObject entity){
                getHibernateTemplate().save(entity);
        }

        publicvoid update(finalObject entity){
                getHibernateTemplate().update(entity);
        }

        publicvoid delete(finalObject entity){
                getHibernateTemplate().delete(entity);
        }

        publicObject load(finalClass entity, finalSerializable id){
                return getHibernateTemplate().load(entity, id);
        }

        publicObject get(finalClass entity, finalSerializable id){
                return getHibernateTemplate().get(entity, id);
        }

        publicList findAll(finalClass entity){
                return getHibernateTemplate().find("from " + entity.getName());
        }

        publicList findByNamedQuery(finalString namedQuery){
                return getHibernateTemplate().findByNamedQuery(namedQuery);
        }

        publicList findByNamedQuery(finalString query, finalObject parameter){
                return getHibernateTemplate().findByNamedQuery(query, parameter);
        }

        publicList findByNamedQuery(finalString query, finalObject[] parameters){
                return getHibernateTemplate().findByNamedQuery(query, parameters);
        }

        publicList find(finalString query){
                return getHibernateTemplate().find(query);
        }

        publicList find(finalString query, finalObject parameter){
                return getHibernateTemplate().find(query, parameter);
        }

        public PaginationSupport findPageByCriteria(final DetachedCriteria detachedCriteria){
                return findPageByCriteria(detachedCriteria, PaginationSupport.PAGESIZE, 0);
        }

        public PaginationSupport findPageByCriteria(final DetachedCriteria detachedCriteria, finalint startIndex){
                return findPageByCriteria(detachedCriteria, PaginationSupport.PAGESIZE, startIndex);
        }

        public PaginationSupport findPageByCriteria(final DetachedCriteria detachedCriteria, finalint pageSize,
                        finalint startIndex){
                return(PaginationSupport) getHibernateTemplate().execute(new HibernateCallback(){
                        publicObject doInHibernate(Session session)throws HibernateException {
                                Criteria criteria = detachedCriteria.getExecutableCriteria(session);
                                int totalCount = ((Integer) criteria.setProjection(Projections.rowCount()).uniqueResult()).intValue();
                                criteria.setProjection(null);
                                List items = criteria.setFirstResult(startIndex).setMaxResults(pageSize).list();
                                PaginationSupport ps = new PaginationSupport(items, totalCount, pageSize, startIndex);
                                return ps;
                        }
                }, true);
        }

        publicList findAllByCriteria(final DetachedCriteria detachedCriteria){
                return(List) getHibernateTemplate().execute(new HibernateCallback(){
                        publicObject doInHibernate(Session session)throws HibernateException {
                                Criteria criteria = detachedCriteria.getExecutableCriteria(session);
                                return criteria.list();
                        }
                }, true);
        }

        publicint getCountByCriteria(final DetachedCriteria detachedCriteria){
                Integer count = (Integer) getHibernateTemplate().execute(new HibernateCallback(){
                        publicObject doInHibernate(Session session)throws HibernateException {
                                Criteria criteria = detachedCriteria.getExecutableCriteria(session);
                                return criteria.setProjection(Projections.rowCount()).uniqueResult();
                        }
                }, true);
                return count.intValue();
        }
}





用户在web层构造查询条件detachedCriteria，和可选的startIndex，调用业务bean的相应findByCriteria方法，返回一个PaginationSupport的实例ps。

ps.getItems()得到已分页好的结果集
ps.getIndexes()得到分页索引的数组
ps.getTotalCount()得到总结果数
ps.getStartIndex()当前分页索引
ps.getNextIndex()下一页索引
ps.getPreviousIndex()上一页索引






连续看了两篇robbin有关DetachedCriteria的介绍，感觉真的不错，尤其是上面的示例代码，让我着实觉得该对我原来的分页查询做一下代码重构了。

我把原本我的做法也提供出来供大家讨论吧：

首先，为了实现分页查询，我封装了一个Page类：
java代码:  


/*Created on 2005-4-14*/
package org.flyware.util.page;

/**
* @author Joa
*
*/
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 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 currentPage, int beginIndex){
        this.hasPrePage = hasPrePage;
        this.hasNextPage = hasNextPage;
        this.everyPage = everyPage;
        this.totalPage = totalPage;
        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.
     */
    publicint 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;
    }
   
}




上面的这个Page类对象只是一个完整的Page描述，接下来我写了一个PageUtil，负责对Page对象进行构造：
java代码:  


/*Created on 2005-4-14*/
package org.flyware.util.page;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
* @author Joa
*
*/
public class PageUtil {
   
    private static final Log logger = LogFactory.getLog(PageUtil.class);
   
    /**
     * 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);
       
        returnnew Page(hasPrePage, hasNextPage, 
                                everyPage, totalPage,
                                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;
    }
   

}




上面的这两个对象与具体的业务逻辑无关，可以独立和抽象。

面对一个具体的业务逻辑：分页查询出User，每页10个结果。具体做法如下：
1. 编写一个通用的结果存储类Result，这个类包含一个Page对象的信息，和一个结果集List：
java代码:  


/*Created on 2005-6-13*/
package com.adt.bo;

import java.util.List;

import org.flyware.util.page.Page;

/**
* @author Joa
*/
public class Result {

    private Page page;

    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;
    }

    /**
     * @param content
     *            The content to set.
     */
    public void setContent(List content){
        this.content = content;
    }

    /**
     * @param page
     *            The page to set.
     */
    public void setPage(Page page){
        this.page = page;
    }
}




2. 编写业务逻辑接口，并实现它（UserManager， UserManagerImpl）
java代码:  


/*Created on 2005-7-15*/
package com.adt.service;

import net.sf.hibernate.HibernateException;

import org.flyware.util.page.Page;

import com.adt.bo.Result;

/**
* @author Joa
*/
public interface UserManager {
   
    public Result listUser(Page page)throws HibernateException;

}




java代码:  


/*Created on 2005-7-15*/
package com.adt.service.impl;

import java.util.List;

import net.sf.hibernate.HibernateException;

import org.flyware.util.page.Page;
import org.flyware.util.page.PageUtil;

import com.adt.bo.Result;
import com.adt.dao.UserDAO;
import com.adt.exception.ObjectNotFoundException;
import com.adt.service.UserManager;

/**
* @author Joa
*/
public class UserManagerImpl implements UserManager {
   
    private UserDAO userDAO;

    /**
     * @param userDAO The userDAO to set.
     */
    public void setUserDAO(UserDAO userDAO){
        this.userDAO = userDAO;
    }
   
    /* (non-Javadoc)
     * @see com.adt.service.UserManager#listUser(org.flyware.util.page.Page)
     */
    public Result listUser(Page page)throws HibernateException, ObjectNotFoundException {
        int totalRecords = userDAO.getUserCount();
        if(totalRecords == 0)
            throw new ObjectNotFoundException("userNotExist");
        page = PageUtil.createPage(page, totalRecords);
        List users = userDAO.getUserByPage(page);
        returnnew Result(page, users);
    }

}




其中，UserManagerImpl中调用userDAO的方法实现对User的分页查询，接下来编写UserDAO的代码：
3. UserDAO 和 UserDAOImpl:
java代码:  


/*Created on 2005-7-15*/
package com.adt.dao;

import java.util.List;

import org.flyware.util.page.Page;

import net.sf.hibernate.HibernateException;

/**
* @author Joa
*/
public interface UserDAO extends BaseDAO {
   
    public List getUserByName(String name)throws HibernateException;
   
    public int getUserCount()throws HibernateException;
   
    public List getUserByPage(Page page)throws HibernateException;

}




java代码:  


/*Created on 2005-7-15*/
package com.adt.dao.impl;

import java.util.List;

import org.flyware.util.page.Page;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.Query;

import com.adt.dao.UserDAO;

/**
* @author Joa
*/
public class UserDAOImpl extends BaseDAOHibernateImpl implements UserDAO {

    /* (non-Javadoc)
     * @see com.adt.dao.UserDAO#getUserByName(java.lang.String)
     */
    public List getUserByName(String name)throws HibernateException {
        String querySentence = "FROM user in class com.adt.po.User WHERE user.name=:name";
        Query query = getSession().createQuery(querySentence);
        query.setParameter("name", name);
        return query.list();
    }

    /* (non-Javadoc)
     * @see com.adt.dao.UserDAO#getUserCount()
     */
    public int getUserCount()throws HibernateException {
        int count = 0;
        String querySentence = "SELECT count(*) FROM user in class com.adt.po.User";
        Query query = getSession().createQuery(querySentence);
        count = ((Integer)query.iterate().next()).intValue();
        return count;
    }

    /* (non-Javadoc)
     * @see com.adt.dao.UserDAO#getUserByPage(org.flyware.util.page.Page)
     */
    public List getUserByPage(Page page)throws HibernateException {
        String querySentence = "FROM user in class com.adt.po.User";
        Query query = getSession().createQuery(querySentence);
        query.setFirstResult(page.getBeginIndex())
                .setMaxResults(page.getEveryPage());
        return query.list();
    }

}




至此，一个完整的分页程序完成。前台的只需要调用userManager.listUser(page)即可得到一个Page对象和结果集对象的综合体，而传入的参数page对象则可以由前台传入，如果用webwork，甚至可以直接在配置文件中指定。

下面给出一个webwork调用示例：
java代码:  


/*Created on 2005-6-17*/
package com.adt.action.user;

import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.flyware.util.page.Page;

import com.adt.bo.Result;
import com.adt.service.UserService;
import com.opensymphony.xwork.Action;

/**
* @author Joa
*/
public class ListUser implementsAction{

    private static final Log logger = LogFactory.getLog(ListUser.class);

    private UserService userService;

    private Page page;

    privateList users;

    /*
     * (non-Javadoc)
     *
     * @see com.opensymphony.xwork.Action#execute()
     */
    public String execute()throwsException{
        Result result = userService.listUser(page);
        page = result.getPage();
        users = result.getContent();
        return SUCCESS;
    }

    /**
     * @return Returns the page.
     */
    public Page getPage(){
        return page;
    }

    /**
     * @return Returns the users.
     */
    public List getUsers(){
        return users;
    }

    /**
     * @param page
     *            The page to set.
     */
    public void setPage(Page page){
        this.page = page;
    }

    /**
     * @param users
     *            The users to set.
     */
    public void setUsers(List users){
        this.users = users;
    }

    /**
     * @param userService
     *            The userService to set.
     */
    public void setUserService(UserService userService){
        this.userService = userService;
    }
}




上面的代码似乎看不出什么地方设置了page的相关初值，事实上，可以通过配置文件来进行配置，例如，我想每页显示10条记录，那么只需要：
java代码:  


<?xml version="1.0"?>
<!DOCTYPE xwork PUBLIC "-//OpenSymphony Group//XWork 1.0//EN" "http://www.opensymphony.com/xwork/xwork-1.0.dtd">

<xwork>
       
        <package name="user" extends="webwork-interceptors">
               
                <!-- The default interceptor stack name -->
        <default-interceptor-ref name="myDefaultWebStack"/>
               
                <action name="listUser" class="com.adt.action.user.ListUser">
                        <param name="page.everyPage">10</param>
                        <result name="success">/user/user_list.jsp</result>
                </action>
               
        </package>

</xwork>





这样就可以通过配置文件和OGNL的共同作用来对page对象设置初值了。并可以通过随意修改配置文件来修改每页需要显示的记录数。

注：上面的<param>的配置，还需要webwork和Spring整合的配合。




我写的一个用于分页的类，用了泛型了，hoho

java代码:  


package com.intokr.util;

import java.util.List;

/**
* 用于分页的类<br>
* 可以用于传递查询的结果也可以用于传送查询的参数<br>
*
* @version 0.01
* @author cheng
*/
public class Paginator<E> {
       private int count = 0; // 总记录数
        private int p = 1; // 页编号
        private int num = 20; // 每页的记录数
        private List<E> results = null; // 结果

        /**
        * 结果总数
        */
        public int getCount(){
                return count;
        }

        public void setCount(int count){
                this.count = count;
        }

        /**
        * 本结果所在的页码，从1开始
        *
        * @return Returns the pageNo.
        */
        public int getP(){
                return p;
        }

        /**
        * if(p<=0) p=1
        *
        * @param p
        */
        public void setP(int p){
                if(p <= 0)
                        p = 1;
                this.p = p;
        }

        /**
        * 每页记录数量
        */
        public int getNum(){
                return num;
        }

        /**
        * if(num<1) num=1
        */
        public void setNum(int num){
                if(num < 1)
                        num = 1;
                this.num = num;
        }

        /**
        * 获得总页数
        */
        public int getPageNum(){
                return(count - 1) / num + 1;
        }

        /**
        * 获得本页的开始编号，为 (p-1)*num+1
        */
        public int getStart(){
                return(p - 1) * num + 1;
        }

        /**
        * @return Returns the results.
        */
        public List<E> getResults(){
                return results;
        }

        public void setResults(List<E> results){
                this.results = results;
        }

        public String toString(){
                StringBuilder buff = new StringBuilder();
                buff.append("{");
                buff.append("count:").append(count);
                buff.append(",p:").append(p);
                buff.append(",nump:").append(num);
                buff.append(",results:").append(results);
                buff.append("}");
                return buff.toString();
        }

}