Hibernate分页查询
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package org.heardy.dao.impl;import java.util.List;import javax.annotation.Resource;import org.heardy.dao.GenericDao;import org.hibernate.Criteria;import org.hibernate.SessionFactory;import org.hibernate.criterion.CriteriaSpecification;import org.hibernate.criterion.DetachedCriteria;import org.hibernate.criterion.Projections;import org.springframework.stereotype.Repository;import org.springframework.transaction.annotation.Transactional;@Repository("genericDao")/* * 只在单元测试时使用 */@Transactionalpublic class GenericDaoImpl implements GenericDao {@ResourceSessionFactory sessionFactory;public Object uniqueResult(DetachedCriteria dc) {Criteria criteria = dc.getExecutableCriteria(sessionFactory.getCurrentSession());return criteria.uniqueResult();}public List<?> dynamicQuery(DetachedCriteria dc) {Criteria criteria = dc.getExecutableCriteria(sessionFactory.getCurrentSession());return criteria.list();}// criteria.setProjection(Projections.projectionList().add(Projections.rowCount()));// //查询总行数// criteria.add(Projections.avg(propertyName)); //求平构值// criteria.add(Projections.min(propertyName)); //最小值// criteria.add(Projections.max(propertyName)); //最大值// criteria.add(Projections.sum(propertyName)); //求和// criteria.add(Projections.groupProperty(propertyName)); //分组public Integer sum(DetachedCriteria dc, String propertyName) {Criteria criteria = dc.getExecutableCriteria(sessionFactory.getCurrentSession());Integer sum = (Integer) criteria.setProjection(Projections.sum(propertyName)).uniqueResult();criteria.setProjection(null);criteria.setResultTransformer(CriteriaSpecification.ROOT_ENTITY);// 如果查询的对象有外键,需要添加此语句return sum;}public Integer count(DetachedCriteria dc) {Criteria criteria = dc.getExecutableCriteria(sessionFactory.getCurrentSession());Integer totalCount = (Integer) criteria.setProjection(Projections.rowCount()).uniqueResult();criteria.setProjection(null);criteria.setResultTransformer(CriteriaSpecification.ROOT_ENTITY);// 如果查询的对象有外键,需要添加此语句return totalCount;}public List<?> pageQuery(DetachedCriteria dc, int limit, int start) {Criteria criteria = dc.getExecutableCriteria(sessionFactory.getCurrentSession());criteria.setFirstResult(start);criteria.setMaxResults(limit);return criteria.list();}}
package org.heardy.service.impl;import java.util.ArrayList;import java.util.List;import javax.annotation.Resource;import org.heardy.bean.PageBean;import org.heardy.dao.GenericDao;import org.heardy.service.GenericService;import org.heardy.tool.TypeChange;import org.hibernate.criterion.DetachedCriteria;import org.springframework.transaction.annotation.Propagation;import org.springframework.transaction.annotation.Transactional;@Transactionalpublic abstract class GenericServiceImpl implements GenericService {@ResourceGenericDao genericDao;@Transactional(propagation = Propagation.NOT_SUPPORTED, readOnly = true)public PageBean findPageList(DetachedCriteria dc, PageBean page) {int count = TypeChange.objectToInt(genericDao.count(dc));@SuppressWarnings("rawtypes")List<?> purchases = new ArrayList();if (page.getLimit() != 0) {purchases = genericDao.pageQuery(dc, page.getLimit(),page.getStart());}page.setResult(count, purchases);return page;}public Integer getCount(DetachedCriteria dc) {return TypeChange.objectToInt(genericDao.count(dc));}public List<?> findAllList(DetachedCriteria dc) {return genericDao.dynamicQuery(dc);}public Object findBean(DetachedCriteria dc) {return genericDao.uniqueResult(dc);}}
在hibernate中,在查询总数时,会使用如下方法;
public Integer getCount(final DetachedCriteria detachedCriteria) {
return (Integer) getHibernateTemplate().execute(new HibernateCallback() {
@Override
public Object doInHibernate(Session session)
throws HibernateException, SQLException {
Criteria criteria = detachedCriteria.getExecutableCriteria(session);
int totalCount = (Integer) criteria.setProjection(
Projections.rowCount()).uniqueResult();
criteria.setProjection(null);
//
criteria.setResultTransformer(CriteriaSpecification.ROOT_ENTITY);
return totalCount;
}
}, true);
}
有时在int totalCount = (Integer) criteria.setProjection(
Projections.rowCount()).uniqueResult();这一句会报NullPointException。
原因是这句代码之前出现了criteria.addOrder(Order.desc("sc.createTime"));这样的排序语句。
把排序语句放到总数查询的后面即可。有时候你注释了缓存也仍然会影响的,需要把注释的语句也删掉。
--------------------------------通用的记录查询总数-------------------------------------------
protected <T> int countQueryResult(Criteria c) {
CriteriaImpl impl = (CriteriaImpl) c;
// 先把Projection、OrderBy、ResultTransformer取出来,清空三者后再执行Count操作
Projection projection = impl.getProjection();
ResultTransformer transformer = impl.getResultTransformer();
List<CriteriaImpl.OrderEntry> orderEntries;
try {
orderEntries = (List) BeanUtils.forceGetProperty(impl, "orderEntries");
BeanUtils.forceSetProperty(impl, "orderEntries", new ArrayList());
} catch (Exception e) {
throw new InternalError(" Runtime Exception impossibility throw ");
}
// 执行Count查询
long totalCount = (Long) c.setProjection(Projections.rowCount()).uniqueResult();
// 将之前的Projection和OrderBy条件重新设回去
c.setProjection(projection);
if (projection == null) {
c.setResultTransformer(CriteriaSpecification.ROOT_ENTITY);
}
if (transformer != null) {
c.setResultTransformer(transformer);
}
try {
BeanUtils.forceSetProperty(impl, "orderEntries", orderEntries);
} catch (Exception e) {
throw new InternalError(" Runtime Exception impossibility throw ");
}
return Integer.valueOf(String.valueOf(totalCount));
}
CriteriaImpl impl = (CriteriaImpl) c;
// 先把Projection、ResultTransformer、OrderBy取出来,清空三者后再执行Count操作
Projection projection = impl.getProjection();
ResultTransformer transformer = impl.getResultTransformer();
List<CriteriaImpl.OrderEntry> orderEntries = null;
try {
orderEntries = (List) ReflectionUtils.getFieldValue(impl, "orderEntries");
ReflectionUtils.setFieldValue(impl, "orderEntries", new ArrayList());
} catch (Exception e) {
logger.error("不可能抛出的异常:{}", e.getMessage());
}
// 执行Count查询
int totalCount = (Integer) c.setProjection(Projections.rowCount()).uniqueResult();
// 将之前的Projection,ResultTransformer和OrderBy条件重新设回去
c.setProjection(projection);
if (projection == null) {
c.setResultTransformer(CriteriaSpecification.ROOT_ENTITY);
}
if (transformer != null) {
c.setResultTransformer(transformer);
}
try {
ReflectionUtils.setFieldValue(impl, "orderEntries", orderEntries);
} catch (Exception e) {
logger.error("不可能抛出的异常:{}", e.getMessage());
}
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