在 Groovy 脚本中使用 @Field 变量

Question

I have a script with a global variable in my Groovy script I have a problem using it inside a function. May I know the reason or the right way? I'm gonna be using it for a logger. Other primitive data types can be accessed but this, I can't.

@Field def log = Logger.getLogger("NameOfLogger")

log.info("TEST")

testFunction()

private void testFunction() {
 //cannot use the log variable here
}

Answer 1

I know now the cause. It's because I was declaring it as def But I still don't know the real reason why def can't be used.

Answer 2

The following code works for me (I haven't tried with log but used online groovy console):

import groovy.transform.Field
import groovy.transform.Canonical

@Canonical
class Person {
   String name
   int age
}

@Field person = new Person("John", 30)
println "Global $person"

testFunction()  

private void testFunction() {
   println "Inside method: $person"
}​

Output:

Global Person(John, 30)
Inside method: Person(John, 30)

So make sure you have proper imports first of all

Now, it worth mentioning that groovy creates an implicit class and Field annotation alters the scope of the global variable and moves it to be a field of that implicit class so that both person and testFunction will both belong to this class and there won't be a problem to access the field from within the method.