Hibernate分页

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 <st1:chsdate year="2005" month="4" day="14" islunardate="False" isrocdate="False" w:st="on">2005-4-14</st1:chsdate>*/
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.
     */
    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;
    }
   
}

<o:p> </o:p>

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 <st1:chsdate year="2005" month="4" day="14" islunardate="False" isrocdate="False" w:st="on">2005-4-14</st1:chsdate>*/
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);
       
        return new 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;
    }
   

}

<o:p> </o:p>

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 <st1:chsdate year="2005" month="6" day="13" islunardate="False" isrocdate="False" w:st="on">2005-6-13</st1:chsdate>*/
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;
    }
}

<o:p> </o:p>

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

java代码: 

/*Created on <st1:chsdate year="2005" month="7" day="15" islunardate="False" isrocdate="False" w:st="on">2005-7-15</st1:chsdate>*/
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;

}

<o:p> </o:p>

<o:p> </o:p>

java代码: 

/*Created on <st1:chsdate year="2005" month="7" day="15" islunardate="False" isrocdate="False" w:st="on">2005-7-15</st1:chsdate>*/
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);
        return new Result(page, users);
    }

}

<o:p> </o:p>

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 <st1:chsdate year="2005" month="7" day="15" islunardate="False" isrocdate="False" w:st="on">2005-7-15</st1:chsdate>*/
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;

}

<o:p> </o:p>

<o:p> </o:p>

java代码: 

/*Created on <st1:chsdate year="2005" month="7" day="15" islunardate="False" isrocdate="False" w:st="on">2005-7-15</st1:chsdate>*/
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();
    }

}

<o:p> </o:p>

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 <st1:chsdate year="2005" month="6" day="17" islunardate="False" isrocdate="False" w:st="on">2005-6-17</st1:chsdate>*/
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 implements Action {

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

    private UserService userService;

    private Page page;

    private List users;

    /*
     * (non-Javadoc)
     *
     * @see com.opensymphony.xwork.Action＃e xecute()
     */
    public String execute() throws Exception {
        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;
    }
}

<o:p> </o:p>

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>

<o:p> </o:p>

 

来源:http://forum.iteye.com/viewtopic.php?t=14657

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。