Struts 2+Hibernate分页代码

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
*
*/
publicclass Page {
    
    /** imply if the page has previous page */
    privateboolean hasPrePage;
    
    /** imply if the page has next page */
    privateboolean hasNextPage;
        
    /** the number of every page */
    privateint everyPage;
    
    /** the total page number */
    privateint totalPage;
        
    /** the number of current page */
    privateint currentPage;
    
    /** the begin index of the records by the current query */
    privateint 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.
     */
    publicint getBeginIndex(){
        return beginIndex;
    }
    
    /**
     * @param beginIndex
     * The beginIndex to set.
     */
    publicvoid setBeginIndex(int beginIndex){
        this.beginIndex = beginIndex;
    }
    
    /**
     * @return
     * Returns the currentPage.
     */
    publicint getCurrentPage(){
        return currentPage;
    }
    
    /**
     * @param currentPage
     * The currentPage to set.
     */
    publicvoid setCurrentPage(int currentPage){
        this.currentPage = currentPage;
    }
    
    /**
     * @return
     * Returns the everyPage.
     */
    publicint getEveryPage(){
        return everyPage;
    }
    
    /**
     * @param everyPage
     * The everyPage to set.
     */
    publicvoid setEveryPage(int everyPage){
        this.everyPage = everyPage;
    }
    
    /**
     * @return
     * Returns the hasNextPage.
     */
    publicboolean getHasNextPage(){
        return hasNextPage;
    }
    
    /**
     * @param hasNextPage
     * The hasNextPage to set.
     */
    publicvoid setHasNextPage(boolean hasNextPage){
        this.hasNextPage = hasNextPage;
    }
    
    /**
     * @return
     * Returns the hasPrePage.
     */
    publicboolean getHasPrePage(){
        return hasPrePage;
    }
    
    /**
     * @param hasPrePage
     * The hasPrePage to set.
     */
    publicvoid setHasPrePage(boolean hasPrePage){
        this.hasPrePage = hasPrePage;
    }
    
    /**
     * @return Returns the totalPage.
     *
     */
    publicint getTotalPage(){
        return totalPage;
    }
    
    /**
     * @param totalPage
     * The totalPage to set.
     */
    publicvoid 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
*
*/
publicclass PageUtil {
    
    privatestaticfinal Log logger = LogFactory.getLog(PageUtil.class);
    
    /**
     * Use the origin page to create a new page
     * @param page
     * @param totalRecords
     * @return
     */
    publicstatic 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
     */
    publicstatic 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);
    }
    
    privatestaticint getEveryPage(int everyPage){
        return everyPage == 0 ? 10 : everyPage;
    }
    
    privatestaticint getCurrentPage(int currentPage){
        return currentPage == 0 ? 1 : currentPage;
    }
    
    privatestaticint getBeginIndex(int everyPage, int currentPage){
        return(currentPage - 1) * everyPage;
    }
        
    privatestaticint getTotalPage(int everyPage, int totalRecords){
        int totalPage = 0;
                
        if(totalRecords % everyPage == 0)
            totalPage = totalRecords / everyPage;
        else
            totalPage = totalRecords / everyPage + 1 ;
                
        return totalPage;
    }
    
    privatestaticboolean hasPrePage(int currentPage){
        return currentPage == 1 ? false : true;
    }
    
    privatestaticboolean 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
*/
publicclass Result {
    private Page page;
    privateList 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.
     */
    publicList getContent(){
        return content;
    }
    /**
     * @return Returns the page.
     */
    public Page getPage(){
        return page;
    }
    /**
     * @param content
     *            The content to set.
     */
    publicvoid setContent(List content){
        this.content = content;
    }
    /**
     * @param page
     *            The page to set.
     */
    publicvoid 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
*/
publicinterface 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
*/
publicclass UserManagerImpl implements UserManager {
    
    private UserDAO userDAO;
    /**
     * @param userDAO The userDAO to set.
     */
    publicvoid 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
*/
publicinterface UserDAO extends BaseDAO {
    
    publicList getUserByName(String name)throws HibernateException;
    
    publicint getUserCount()throws HibernateException;
    
    publicList 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
*/
publicclass UserDAOImpl extends BaseDAOHibernateImpl implements UserDAO {
    /* (non-Javadoc)
     * @see com.adt.dao.UserDAO#getUserByName(java.lang.String)
     */
    publicList 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()
     */
    publicint 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)
     */
    publicList 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
*/
publicclass ListUser implementsAction{
    privatestaticfinal Log logger = LogFactory.getLog(ListUser.class);
    private UserService userService;
    private Page page;
    privateList users;
    /*
     * (non-Javadoc)
     *
     * @see com.opensymphony.xwork.Action#execute()
     */
    publicString 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.
     */
    publicList getUsers(){
        return users;
    }
    /**
     * @param page
     *            The page to set.
     */
    publicvoid setPage(Page page){
        this.page = page;
    }
    /**
     * @param users
     *            The users to set.
     */
    publicvoid setUsers(List users){
        this.users = users;
    }
    /**
     * @param userService
     *            The userService to set.
     */
    publicvoid 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 joa*/
publicclass Paginator<E> {
        privateint count = 0; // 总记录数
        privateint p = 1; // 页编号
        privateint num = 20; // 每页的记录数
        privateList<E> results = null; // 结果
        /**
        * 结果总数
        */
        publicint getCount(){
                return count;
        }
        publicvoid setCount(int count){
                this.count = count;
        }
        /**
        * 本结果所在的页码，从1开始
        *
        * @return Returns the pageNo.
        */
        publicint getP(){
                return p;
        }
        /**
        * if(p<=0) p=1
        *
        * @param p
        */
        publicvoid setP(int p){
                if(p <= 0)
                        p = 1;
                this.p = p;
        }
        /**
        * 每页记录数量
        */
        publicint getNum(){
                return num;
        }
        /**
        * if(num<1) num=1
        */
        publicvoid setNum(int num){
                if(num < 1)
                        num = 1;
                this.num = num;
        }
        /**
        * 获得总页数
        */
        publicint getPageNum(){
                return(count - 1) / num + 1;
        }
        /**
        * 获得本页的开始编号，为 (p-1)*num+1
        */
        publicint getStart(){
                return(p - 1) * num + 1;
        }
        /**
        * @return Returns the results.
        */
        publicList<E> getResults(){
                return results;
        }
        publicvoid setResults(List<E> results){
                this.results = results;
        }
        publicString 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();
        }
}