将ParameterExpression与org.springframework.data.jpa.domain.Specification一起使用时，如何将参数传递给函数? [英] How to pass an argument to a function when using ParameterExpression together with org.springframework.data.jpa.domain.Specification?

问题描述

我正在使用org.springframework.data.jpa.domain.Specification和JpaSpecificationExecutor来轻松地在Java中创建带有条件的查询，但是现在我需要调用一个返回整数值的MySQL DB函数.

I am using org.springframework.data.jpa.domain.Specification together with JpaSpecificationExecutor to easily create queries with conditions in Java but now I need to call a MySQL DB function that returns an integer value.

问题在于，由于我不使用TypedQuery，因此尚不清楚如何为此函数传递参数:

The problem is that it is unclear how to pass an argument for this function as I am not using TypedQuery:

// cb here is CriteriaBuilder
ParameterExpression param = cb.parameter(String.class);

Predicate predicate = cb.greaterThan(cb.function("A_FUNCTION", 
      Integer.class, param), 0);

Specification spec = cb.and(predicate);

// query is executed like this

return (int) repositoryThatExtendsJpaSpecificationExecutor.count(test);

此处中的示例>没有帮助.

And the example from here is not helping.

推荐答案

我认为您真正需要的是可以使用

I think what you really need is a literal which you can create using CriteriaBuilder.literal. A full example would look like

// cb here is CriteriaBuilder
Expression param = cb.literal("Stephen Hawking");

Predicate predicate = cb.greaterThan(cb.function("A_FUNCTION", 
      Integer.class, param), 0);

Specification spec = cb.and(predicate);

如果该值不是来自您的应用程序，则可以使用(m)任何

If the value doesn't come from your application you can use (m)any of the functions returning an Expression.

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