应用Hibernate3的DetachedCriteria实现分页查询
【IT168技术文档】
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;
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import java.util.List;
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public class PaginationSupport ...{
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public final static int PAGESIZE = 30;
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private int pageSize = PAGESIZE;
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private List items;
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private int totalCount;
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private int[] indexes = new int[0];
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private int startIndex = 0;
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public PaginationSupport(List items, int totalCount) ...{
setPageSize(PAGESIZE);
setTotalCount(totalCount);
setItems(items);
setStartIndex(0);
}
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public PaginationSupport(List items, int totalCount, int startIndex) ...{
setPageSize(PAGESIZE);
setTotalCount(totalCount);
setItems(items);
setStartIndex(startIndex);
}
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public PaginationSupport(List items, int totalCount, int pageSize,
int startIndex) ...{setPageSize(pageSize);
setTotalCount(totalCount);
setItems(items);
setStartIndex(startIndex);
}
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public List getItems() ...{
return items;
}
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public void setItems(List items) ...{
this.items = items;
}
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public int getPageSize() ...{
return pageSize;
}
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public void setPageSize(int pageSize) ...{
this.pageSize = pageSize;
}
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public int getTotalCount() ...{
return totalCount;
}
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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;
}
}
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public int[] getIndexes() ...{
return indexes;
}
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public void setIndexes(int[] indexes) ...{
this.indexes = indexes;
}
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public int getStartIndex() ...{
return startIndex;
}
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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];
}
}
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public int getNextIndex() ...{
int nextIndex = getStartIndex() + pageSize;
if (nextIndex >= totalCount)
return getStartIndex();
else
return nextIndex;
}
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public int getPreviousIndex() ...{
int previousIndex = getStartIndex() - pageSize;
if (previousIndex < 0)
return 0;
else
return previousIndex;
}
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}
【IT168技术文档】
抽象业务类
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。/**//**
* Created on 2005-7-12
*/
package com.javaeye.common.business;
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import java.io.Serializable;
import java.util.List;
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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;
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import com.javaeye.common.util.PaginationSupport;
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public abstract class AbstractManager extends HibernateDaoSupport ...{
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private boolean cacheQueries = false;
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private String queryCacheRegion;
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public void setCacheQueries(boolean cacheQueries) ...{
this.cacheQueries = cacheQueries;
}
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public void setQueryCacheRegion(String queryCacheRegion) ...{
this.queryCacheRegion = queryCacheRegion;
}
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public void save(final Object entity) ...{
getHibernateTemplate().save(entity);
}
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public void persist(final Object entity) ...{
getHibernateTemplate().save(entity);
}
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public void update(final Object entity) ...{
getHibernateTemplate().update(entity);
}
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public void delete(final Object entity) ...{
getHibernateTemplate().delete(entity);
}
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public Object load(final Class entity, final Serializable id) ...{
return getHibernateTemplate().load(entity, id);
}
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public Object get(final Class entity, final Serializable id) ...{
return getHibernateTemplate().get(entity, id);
}
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public List findAll(final Class entity) ...{
return getHibernateTemplate().find("from " + entity.getName());
}
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public List findByNamedQuery(final String namedQuery) ...{
return getHibernateTemplate().findByNamedQuery(namedQuery);
}
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public List findByNamedQuery(final String query, final Object parameter) ...{
return getHibernateTemplate().findByNamedQuery(query, parameter);
}
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public List findByNamedQuery(final String query, final Object[] parameters)
{return getHibernateTemplate().findByNamedQuery(query, parameters);
}
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public List find(final String query) ...{
return getHibernateTemplate().find(query);
}
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public List find(final String query, final Object parameter) ...{
return getHibernateTemplate().find(query, parameter);
}
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public PaginationSupport findPageByCriteria(final DetachedCriteria
detachedCriteria)
...{return findPageByCriteria(detachedCriteria, PaginationSupport.PAGESIZE, 0);
}
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public PaginationSupport findPageByCriteria(final DetachedCriteria
detachedCriteria,
final int startIndex) ...{return findPageByCriteria(detachedCriteria, PaginationSupport.PAGESIZE,
startIndex);}
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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);
}
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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);
}
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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();
}
}
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
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