【IT168 技术文档】

　　今天把myblog用sql server部署了一下，可是发现分页查询的时候出现错误，看控制台报错说语句有错,由来发现分页的时候先查询总记录数目的那条语句出错了：
select count(*) as y0_ from myblog_Blog this_ inner join myblog_Blog_Category categories3_ on this_.id=categories3_.blogId inner join myblog_Category category1_ on categories3_.categoryId=category1_.id where category1_.id=? order by this_.postTime desc     

　　原来开发的时候我是用的mysql，没有任何问题。原因就在最后面的order by 语句，sql server 在select count(*)里面不能用 order by。然后跟踪代码发现：

    public PaginationSupport getBlogsByCategoryByPage(
final String categoryId, final int startIndex,
final int pageSize) {
return (PaginationSupport) getHibernateTemplate().
execute(new HibernateCallback() {
public Object doInHibernate(Session session)
throws HibernateException {
Criteria criteria = session.createCriteria(Blog.class);
Criteria cateCriteria = criteria.createCriteria("categories");
cateCriteria.add(Expression.eq("id",categoryId));
criteria.addOrder(Order.desc("postTime"));
int totalCount = ((Integer) criteria.setProjection(
Projections.rowCount())
.uniqueResult()).intValue();
criteria.setProjection(null);
List items = criteria.setFirstResult(startIndex).
setMaxResults(pageSize).list();
List blogs = new ArrayList();
for(Iterator ite = items.iterator(); ite.hasNext();) {
Object[] objs = (Object[])ite.next();
blogs.add(objs[1]);
}
PaginationSupport ps = new PaginationSupport(
blogs, totalCount, pageSize, startIndex);
return ps;
}
}, true);
}

　　原来问题就在Criteria.addOrder(Order.desc("postTime"));这句话的位置上面，

int totalCount = ((Integer) criteria.setProjection(Projections.rowCount())
.uniqueResult()).intValue();

    public PaginationSupport getBlogsByCategoryByPage(
final String categoryId, final int startIndex,
final int pageSize) {
return (PaginationSupport) getHibernateTemplate().execute(new HibernateCallback() {
public Object doInHibernate(Session session) throws HibernateException {
Criteria criteria = session.createCriteria(Blog.class);
Criteria cateCriteria = criteria.createCriteria("categories");
cateCriteria.add(Expression.eq("id",categoryId));
int totalCount = ((Integer) criteria.setProjection(Projections.rowCount())
.uniqueResult()).intValue();
criteria.setProjection(null);
/*
* Fix a bug ,Order must add after get the totalCount,
* beacuse SqlServer not support order by in the select count(*).
*/
criteria.addOrder(Order.desc("postTime"));
List items = criteria.setFirstResult(startIndex).setMaxResults(pageSize).list();
List blogs = new ArrayList();
for(Iterator ite = items.iterator(); ite.hasNext();) {
Object[] objs = (Object[])ite.next();
blogs.add(objs[1]);
}
PaginationSupport ps = new PaginationSupport(blogs, totalCount, pageSize, startIndex);
return ps;
}
}, true);
}

　　这样生成的sql语句就是这样的：

select count(*) as y0_ from myblog_Blog this_ inner join myblog_Blog_Category categories3_ on this_.id=categories3_.blogId inner join myblog_Category category1_ on categories3_.categoryId=category1_.id where category1_.id=?

　　以后大家也要注意了。呵呵。