CODEWITHSUNDEEP
groovymetaprogramming
KyrinWoo
KyrinWoo

Reputation: 347

Groovy: got StackOverflowError by invokeMethod within Interceptor

A class named InterceptorTest implementing GroovyInterceptable,which could be an interceptor,has its invokeMethod overrided as follows:

class InterceptorTest implements GroovyInterceptable{
    def invokeMethod(String name,args){
        println "intercepting call! " //println a short message
    }
}

I thought class InterceptorTest to be an interceptor would delegate all method calls to invokeMethod,so the following should work:

def interceptor=new InterceptorTest()
println interceptor.work()

Unfortunately, I got a StackOverflowError，seemingly at the body of invokeMethod,but I had no clue why it happened.

As a counterpart, I altered the function body,not println but just return message:

class InterceptorTest implements GroovyInterceptable{
    def invokeMethod(String name,args){
        "intercepting call! " //return a short message
    }
}

then it worked fine:

def interceptor=new InterceptorTest()
println interceptor.work()  //get "intercepting call!"

But WHY?

Upvotes: 1

Views: 100

Answers (1)

Corrodias
Corrodias

Reputation: 784

According to the documentation, "println" is actually a method in the class, injected by Groovy. Therefore, you achieve infinite recursion by trying to call it within the invokeMethod function.

We cannot use default groovy methods like println because these methods are injected into all Groovy objects so they will be intercepted too.

Upvotes: 1

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