struts+hibernate分页[转贴]

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Hibernate Struts Bean ORM Apache

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; 

publicclass PaginationSupport {

publicfinalstaticint 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.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; 

publicabstractclass AbstractManager extends HibernateDaoSupport {

privateboolean cacheQueries = false; 

privateString 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 
* 
*/
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)color: rgb(0,

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