我想使用CriteriaBuilder構建下面顯示的having子句：

select objectid,

sum(case when attr_meta = 'severity' then 1 else 0 end) as severity,

sum(case when attr_meta = 'priority' then 1 else 0 end) as priority

from object d

group by objectid

having sum(case when attr_meta = 'severity' then 1 else 0 end) != 1

or sum(case when attr_meta = 'priority' then 1 else 0 end) != 1;

我嘗試了以下方法：

Predicate p = cb.equal(cb.sum(cb.selectCase()

.when(cb.equal(root.get("name"), 'severity'), 1).otherwise(0)), 1);

p = cb.or(p, cb.equal(cb.sum(cb.selectCase()

.when(cb.equal(root.get("name"), 'priority'), 1).otherwise(0)), 1));

但這給出了以下例外：

java.lang.NullPointerException

at java.lang.Class.isAssignableFrom(Native Method)

at org.hibernate.ejb.criteria.ValueHandlerFactory.isNumeric(ValueHandlerFactory.java:70)

at org.hibernate.ejb.criteria.predicate.ComparisonPredicate.(ComparisonPredicate.java:69)

at org.hibernate.ejb.criteria.CriteriaBuilderImpl.equal(CriteriaBuilderImpl.java:392)

異常似乎來自外部CriteriaBuilderImpl.equal()調用,它包含selectCase()調用.

內部的equal()調用需要Expression的類型信息. selectCase()調用在創建Expression時,將type設置為null.我們有辦法處理這種情況嗎？讓equ()知道類型的方法,或者對上述查詢采用完全不同的方法？