技术开发 频道

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; 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; } }

IT168技术文档】 
    抽象业务类
/** * 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

0
相关文章