Immutablizable by trait

trait.groovy

trait Immutable {
    void setProperty(String property, Object o) {
        throw new UnsupportedOperationException("$property is immutable: $o")
    }
}

class Hello {
    String hello(String name) { "$message, $name!" }
    String getMessage() { "Hello" }
    String setHoge(Object o) { "Set!(Duumy)" }
}

def h = new Hello()
assert h.hello("Bar") == "Hello, Bar!"
assert h.message == "Hello"
h.hoge = 123

def ih = h as Immutable
assert ih.hello("Bar") == "Hello, Bar!"
assert ih.message == "Hello"
ih.hoge = 123 //=> java.lang.UnsupportedOperationException: hoge is immutable: 123