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Method handle invoke special
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package main; | |
import bar.Bar; | |
import qux.Qux; | |
import java.lang.invoke.MethodHandles; | |
import java.lang.invoke.MethodType; | |
import java.lang.reflect.Proxy; | |
import java.util.function.Consumer; | |
public class Main { | |
public static void main(String[] args) { | |
test(Foo.class, Foo::foo); // interface in same module | |
test(Bar.class, Bar::foo); // interface in other module, exported | |
test(Qux.class, Qux::foo); // interface in other module, exported and opened | |
} | |
private static <T> void test(Class<? extends T> iface, Consumer<T> consumer) { | |
Object instance = Proxy.newProxyInstance( | |
Bar.class.getClassLoader(), | |
new Class<?>[]{iface}, | |
(proxy, method, args) -> { | |
MethodHandles.Lookup lookup; | |
if (proxy.getClass().getModule().isNamed()) { | |
lookup = MethodHandles.privateLookupIn(iface, MethodHandles.lookup()); | |
} else { | |
Main.class.getModule().addReads(proxy.getClass().getModule()); | |
lookup = MethodHandles.privateLookupIn(proxy.getClass(), MethodHandles.lookup()); | |
} | |
return lookup.findSpecial( | |
iface, | |
"foo", | |
MethodType.methodType(String.class, new Class<?>[0]), | |
iface | |
).bindTo(proxy).invokeWithArguments(); | |
} | |
); | |
test(iface, iface.cast(instance), consumer); | |
} | |
private static <T> void test(Class<? extends T> iface, T instance, Consumer<T> consumer) { | |
try { | |
consumer.accept(instance); | |
System.out.println("Could invoke special method for " + iface); | |
} catch (Throwable throwable) { | |
System.out.println("Could NOT invoke special method for " + iface); | |
} | |
} | |
} |
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