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Spring expression (SpEL) - Elvis operator : cannot convert from Integer to Boolean error

I am using Spring expression version 4.3.2.RELEASE It seems we cannot use the Elvis operator for any other types than String and Boolean.

For example, the following will thrown an error: field ?: 2 > 0

  • If field = 1 we get java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Boolean

  • If field is null: then Elvis works correctly and use the value 2.

Can we work around this? is it a defect in SpEL?

thanks,

Sebastien

Solution

  • Elvis operator is shorthand notation for ternary operator, used in case of nullability check.

    Its syntax is:

    someField?:somevalue

    where, someField can be of any type. Above expression will return value of someField (e.g. Integer), if it's not null else it will return someValue. someValue must be of same type as someField (Integer).

    So, This is not a limitation of SPel. It is the specific usage of operator.

    In your example, field is an integer so, resolved value must also be of integer type. But, you are doing 2>0 that resolves to boolean type, which is not valid in this case.

    What you can do is (field?: 2) > 0, if it is what you are trying to achieve.

    I hope, it clarifies.