QueryDsl 如何使用exist() 返回布尔值

Question

I want to upgrade queryDsl from verision 3 to version 4. But i've an issue with exist() In QueryDsl 3 exist return a Boolean but in QUeryDSL 4 it return a BooleanOperation. In my case i really want the boolean but i don't know how to retrieve it.

The best solution i've found is to do

.fetchCount() >0 

But I want to know if another (better) solution exist.

Answer 1

Another option would be something like:

queryFactory.select(queryField).from(qTable)
            .where(queryField.eq(value))
            .groupBy(queryField)
            .having(qTable.uuid.count().gt(0))
            .fetchOne() != null;

This passes the greater than responsibility over to the query. However it is possibly less readible so will depend on the requirements which is better.