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：


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;


}




}



业务抽象类：




/** *//**


* 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