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();
这句话的时候就会生成上面那句话，如果在这之前addOrder就会出现问题，如果你用mysql不会出现问题，如果你用sql server就会报错。解决方法就是把addOrder语句放到totalCount下面就可以了。
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。
