argument types sent to getDeclaredMethod(String, Class[]) in java reflection

Question

i have a method in a class like this:

public static void postEvents(List<RuleEvent> eventList) {
    for(RuleEvent event:eventList)
        if(canProcess(event))
            findListenerAndPost(event);
    }

and i want to access it using reflection like this:

Class partypes[] = new Class[1];
partypes[0] = List.class;    //does not find the method as it is of List<RuleEvent>
postMethod = cls.getMethod("postEvents", partypes);

so, how do I get the class object of List<RuleEvent>????

I already know the way of ((List<RuleEvent>) new ArrayList<RuleEvent>()).getClass() but there should be a more direct way...

Works fine for me. Do you get an error? Due to type erasure there isn't a List<RuleEvent> at runtime. — Dave Newton
– Dave Newton, Commented Jan 2, 2012 at 14:09
Is cls the right class? Null?! You should get a NoSuchMethodException if the method doesn't exist. — Dave Newton
– Dave Newton, Commented Jan 2, 2012 at 14:11
I don't think using a new ArrayList<RuleEvent>().getClass() works either - first of all, since it returns an ArrayList.class rather than List.class, and second, because of type erasure, it still returns a raw ArrayList.class object. — Avi
– Avi, Commented Jan 2, 2012 at 14:19
No, because at runtime, all the generic type information is erased. So the method signature in the JVM is actually postEvents(List). — Avi
– Avi, Commented Jan 2, 2012 at 14:29

Peter Lawrey · Accepted Answer · 2012-01-02 14:51:43Z

9

All you need is the following

cls.getMethod("postEvents", List.class).invoke(null, eventList);

The generic type is not required at runtime.

answered Jan 2, 2012 at 14:51

Peter Lawrey

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