Question

I have some string with Groovy expression. I need:

1. Execute Groovy expression that is contained in java.lang.String
2. Get result of the expression as an Object
3. Determine type of the resulting object

Is it possible? Also, if I won’t use dynamic features of Groovy, will I be able to determine type of the expression “statically”, i.e. in compile-time without executing expression itself.

Thanks

Answer 1

A very simple and easy way is to use the Eval class. Evaluates the specified String expression and returns the result. The type result of the expression is Object.

def object = Eval.me('1 + 1')

You can get the class of an object with the getClass() method or simply:

assert object.class == Integer

In this example, is not possible determine the static type checking at compilation time.

@groovy.transform.TypeChecked
void test() {
    Integer object = Eval.me('1 + 1')
    assert object.class == Integer
}

[Static type checking] - Cannot assign value of type java.lang.Object to variable of type java.lang.Integer