偷窥struts+hibernate分页(第二种方法)

时间: 2005-7-15 17:58:16 标题: 应用Hibernate3的DetachedCriteria实现分页查询

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. javaeye. common. util;

import java. util. List;

public class PaginationSupport {

public final static int PAGESIZE = 30;

private int pageSize = PAGESIZE;

private List items;

private int totalCount;

private int [ ] indexes = new int [ 0 ];

private int 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 );
}

public List getItems ( ) {
return items;
}

public void setItems ( List items ) {
this. items = items;
}

public int getPageSize ( ) {
return pageSize;
}

public void setPageSize ( int pageSize ) {
this. pageSize = pageSize;
}

public int getTotalCount ( ) {
return totalCount;
}

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

public int [ ] getIndexes ( ) {
return indexes;
}

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

public int getStartIndex ( ) {
return startIndex;
}

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

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

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

}

抽象业务类

java代码:

/**
* Created on 2005-7-12
*/
package com. javaeye. 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. javaeye. common. util. PaginationSupport;

public abstract class AbstractManager extends HibernateDaoSupport {

private boolean cacheQueries = false;

private String queryCacheRegion;

public void setCacheQueries ( boolean cacheQueries ) {
this. cacheQueries = cacheQueries;
}

public void setQueryCacheRegion ( String queryCacheRegion ) {
this. queryCacheRegion = queryCacheRegion;
}

public void save ( final Object entity ) {
getHibernateTemplate ( ). save (entity );
}

public void persist ( final Object entity ) {
getHibernateTemplate ( ). save (entity );
}

public void update ( final Object entity ) {
getHibernateTemplate ( ). update (entity );
}

public void delete ( final Object entity ) {
getHibernateTemplate ( ). delete (entity );
}

public Object load ( final Class entity, final Serializable id ) {
return getHibernateTemplate ( ). load (entity, id );
}

public Object get ( final Class entity, final Serializable id ) {
return getHibernateTemplate ( ). get (entity, id );
}

public List findAll ( final Class entity ) {
return getHibernateTemplate ( ). find ( "from " + entity. getName ( ) );
}

public List findByNamedQuery ( final String namedQuery ) {
return getHibernateTemplate ( ). findByNamedQuery (namedQuery );
}

public List findByNamedQuery ( final String query, final Object parameter ) {
return getHibernateTemplate ( ). findByNamedQuery (query, parameter );
}

public List findByNamedQuery ( final String query, final Object [ ] parameters ) {
return getHibernateTemplate ( ). findByNamedQuery (query, parameters );
}

public List find ( final String query ) {
return getHibernateTemplate ( ). find (query );
}

public List find ( final String query, final Object parameter ) {
return getHibernateTemplate ( ). find (query, parameter );
}

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

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

public PaginationSupport findPageByCriteria ( final DetachedCriteria detachedCriteria, final int pageSize,
final int startIndex ) {
return (PaginationSupport ) getHibernateTemplate ( ). execute ( new HibernateCallback ( ) {
public Object 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 );
}

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

public int getCountByCriteria ( final DetachedCriteria detachedCriteria ) {
Integer count = ( Integer ) getHibernateTemplate ( ). execute ( new HibernateCallback ( ) {
public Object 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.
*/
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;
}

}

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 );

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;
}

}

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 );
return new 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 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#execute()
*/
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;
}
}

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">


<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 ( );
}

}

偷窥自 http://forum.javaeye.com/

详情请见 http://forum.javaeye.com/viewtopic.php?t=14657

偷窥struts+hibernate分页(第二种方法)

偷窥struts+hibernate分页(第二种方法)

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