Github user blackdrag commented on a diff in the pull request:
https://github.com/apache/groovy/pull/811#discussion_r225299922
--- Diff: src/main/java/org/codehaus/groovy/vmplugin/v9/Java9.java ---
@@ -18,14 +18,78 @@
*/
package org.codehaus.groovy.vmplugin.v9;
+import org.codehaus.groovy.GroovyBugError;
import org.codehaus.groovy.vmplugin.v8.Java8;
+import java.lang.invoke.MethodHandles;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+
/**
- * Java 9 based functions will be added here if needed.
+ * Additional Java 9 based functions will be added here as needed.
*/
public class Java9 extends Java8 {
+
+ private static class LookupHolder {
+ private static final Method PRIVATE_LOOKUP;
+ private static final Constructor<MethodHandles.Lookup>
LOOKUP_Constructor;
+ static {
+ Constructor<MethodHandles.Lookup> lookup = null;
+ Method privateLookup = null;
+ try { // java 9
+ privateLookup =
MethodHandles.class.getMethod("privateLookupIn", Class.class,
MethodHandles.Lookup.class);
+ } catch (final NoSuchMethodException e) { // java 8
+ try {
+ lookup =
MethodHandles.Lookup.class.getDeclaredConstructor(Class.class, Integer.TYPE);
+ if (!lookup.isAccessible()) {
+ lookup.setAccessible(true);
+ }
+ } catch (final NoSuchMethodException ex) {
+ throw new IllegalStateException("Incompatible JVM", e);
+ }
+ }
+ PRIVATE_LOOKUP = privateLookup;
+ LOOKUP_Constructor = lookup;
+ }
+ }
+
+ private static Constructor<MethodHandles.Lookup>
getLookupConstructor() {
+ return LookupHolder.LOOKUP_Constructor;
+ }
+
+ private static Method getPrivateLookup() {
+ return LookupHolder.PRIVATE_LOOKUP;
+ }
+
+ public static MethodHandles.Lookup of(final Class<?> declaringClass) {
+ try {
+ if (getPrivateLookup() != null) {
+ return
MethodHandles.Lookup.class.cast(getPrivateLookup().invoke(null, declaringClass,
MethodHandles.lookup()));
+ }
+ return getLookupConstructor().newInstance(declaringClass,
MethodHandles.Lookup.PRIVATE).in(declaringClass);
--- End diff --
If PRIVATE_LOOKUP lookup never fails as I think, then LOOKUP_Constructor
will be always the same. Not sure if "in"
(https://docs.oracle.com/javase/9/docs/api/java/lang/invoke/MethodHandles.Lookup.html#in-java.lang.Class-)
then can still do something useful.
---
