Spring JPA存储库最近的日期

Question

I have an entity (id, created_date). I want to create a method in my JPARepository that returns the closest row from now. CreatedDate is a ZonedDateTime. I created next methods (the parameter is ZonedTimeDate.now()):

findTopByCreatedDateBefore (returns first created row)

findFirstByCreatedDateBefore (returns first created row (why the same?))

findTopByCreatedDateBeforeOrderByCreatedDateDesc (returns last created row)

findFirstByCreatedDateBeforeOrderByCreatedDateDesc (returns last created row (why the same?))

The last two return what I want but is it the best way to use them? Why are the first two return the same result?

Answer 1

Because the keywords Top and First are both limiting the results to the optional number following it defaulting to 1. So they only define the number of elements to return, not an implicit ordering — mostly because of the fact that no ordering exists, unless you explicitly specify it.

What top and first can't be defined without any ordering semantics as most stores don't guarantee any kind of ordering of the result unless you specify sorting options. Thus, the order of the elements might even vary for each method invocation.

So in the examples you gave, the first two methods restrict the result to exactly one argument.

Answer 2

我只是将PageRequest作为findAll的参数传递，其中page为1，pageSize为1，顺序为DESC “ createdDate”