diff -r d0f7a3e441c4 -r 88ab34b6da6d jdk/src/share/classes/java/lang/invoke/MethodHandleProxies.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/lang/invoke/MethodHandleProxies.java	Thu May 26 17:37:36 2011 -0700
@@ -0,0 +1,257 @@
+/*
+ * Copyright (c) 2008, 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package java.lang.invoke;
+
+import java.lang.reflect.*;
+import sun.invoke.WrapperInstance;
+
+/**
+ * This class consists exclusively of static methods that help adapt
+ * method handles to other JVM types, such as interfaces.
+ */
+public class MethodHandleProxies {
+
+    private MethodHandleProxies() { }  // do not instantiate
+
+    /**
+     * Produces an instance of the given single-method interface which redirects
+     * its calls to the given method handle.
+     * <p>
+     * A single-method interface is an interface which declares a uniquely named method.
+     * When determining the uniquely named method of a single-method interface,
+     * the public {@code Object} methods ({@code toString}, {@code equals}, {@code hashCode})
+     * are disregarded.  For example, {@link java.util.Comparator} is a single-method interface,
+     * even though it re-declares the {@code Object.equals} method.
+     * <p>
+     * The interface must be public.  No additional access checks are performed.
+     * <p>
+     * The resulting instance of the required type will respond to
+     * invocation of the type's uniquely named method by calling
+     * the given target on the incoming arguments,
+     * and returning or throwing whatever the target
+     * returns or throws.  The invocation will be as if by
+     * {@code target.invoke}.
+     * The target's type will be checked before the
+     * instance is created, as if by a call to {@code asType},
+     * which may result in a {@code WrongMethodTypeException}.
+     * <p>
+     * The uniquely named method is allowed to be multiply declared,
+     * with distinct type descriptors.  (E.g., it can be overloaded,
+     * or can possess bridge methods.)  All such declarations are
+     * connected directly to the target method handle.
+     * Argument and return types are adjusted by {@code asType}
+     * for each individual declaration.
+     * <p>
+     * The wrapper instance will implement the requested interface
+     * and its super-types, but no other single-method interfaces.
+     * This means that the instance will not unexpectedly
+     * pass an {@code instanceof} test for any unrequested type.
+     * <p style="font-size:smaller;">
+     * <em>Implementation Note:</em>
+     * Therefore, each instance must implement a unique single-method interface.
+     * Implementations may not bundle together
+     * multiple single-method interfaces onto single implementation classes
+     * in the style of {@link java.awt.AWTEventMulticaster}.
+     * <p>
+     * The method handle may throw an <em>undeclared exception</em>,
+     * which means any checked exception (or other checked throwable)
+     * not declared by the requested type's single abstract method.
+     * If this happens, the throwable will be wrapped in an instance of
+     * {@link java.lang.reflect.UndeclaredThrowableException UndeclaredThrowableException}
+     * and thrown in that wrapped form.
+     * <p>
+     * Like {@link java.lang.Integer#valueOf Integer.valueOf},
+     * {@code asInterfaceInstance} is a factory method whose results are defined
+     * by their behavior.
+     * It is not guaranteed to return a new instance for every call.
+     * <p>
+     * Because of the possibility of {@linkplain java.lang.reflect.Method#isBridge bridge methods}
+     * and other corner cases, the interface may also have several abstract methods
+     * with the same name but having distinct descriptors (types of returns and parameters).
+     * In this case, all the methods are bound in common to the one given target.
+     * The type check and effective {@code asType} conversion is applied to each
+     * method type descriptor, and all abstract methods are bound to the target in common.
+     * Beyond this type check, no further checks are made to determine that the
+     * abstract methods are related in any way.
+     * <p>
+     * Future versions of this API may accept additional types,
+     * such as abstract classes with single abstract methods.
+     * Future versions of this API may also equip wrapper instances
+     * with one or more additional public "marker" interfaces.
+     *
+     * @param target the method handle to invoke from the wrapper
+     * @param intfc the desired type of the wrapper, a single-method interface
+     * @return a correctly-typed wrapper for the given target
+     * @throws NullPointerException if either argument is null
+     * @throws IllegalArgumentException if the {@code intfc} is not a
+     *         valid argument to this method
+     * @throws WrongMethodTypeException if the target cannot
+     *         be converted to the type required by the requested interface
+     */
+    // Other notes to implementors:
+    // <p>
+    // No stable mapping is promised between the single-method interface and
+    // the implementation class C.  Over time, several implementation
+    // classes might be used for the same type.
+    // <p>
+    // If the implementation is able
+    // to prove that a wrapper of the required type
+    // has already been created for a given
+    // method handle, or for another method handle with the
+    // same behavior, the implementation may return that wrapper in place of
+    // a new wrapper.
+    // <p>
+    // This method is designed to apply to common use cases
+    // where a single method handle must interoperate with
+    // an interface that implements a function-like
+    // API.  Additional variations, such as single-abstract-method classes with
+    // private constructors, or interfaces with multiple but related
+    // entry points, must be covered by hand-written or automatically
+    // generated adapter classes.
+    //
+    public static
+    <T> T asInterfaceInstance(final Class<T> intfc, final MethodHandle target) {
+        // POC implementation only; violates the above contract several ways
+        final Method sm = getSingleMethod(intfc);
+        if (sm == null)
+            throw new IllegalArgumentException("not a single-method interface: "+intfc.getName());
+        MethodType smMT = MethodType.methodType(sm.getReturnType(), sm.getParameterTypes());
+        MethodHandle checkTarget = target.asType(smMT);  // make throw WMT
+        checkTarget = checkTarget.asType(checkTarget.type().changeReturnType(Object.class));
+        final MethodHandle vaTarget = checkTarget.asSpreader(Object[].class, smMT.parameterCount());
+        return intfc.cast(Proxy.newProxyInstance(
+                intfc.getClassLoader(),
+                new Class[]{ intfc, WrapperInstance.class },
+                new InvocationHandler() {
+                    private Object getArg(String name) {
+                        if ((Object)name == "getWrapperInstanceTarget")  return target;
+                        if ((Object)name == "getWrapperInstanceType")    return intfc;
+                        throw new AssertionError();
+                    }
+                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
+                        if (method.getDeclaringClass() == WrapperInstance.class)
+                            return getArg(method.getName());
+                        if (method.equals(sm))
+                            return vaTarget.invokeExact(args);
+                        if (isObjectMethod(method))
+                            return callObjectMethod(this, method, args);
+                        throw new InternalError();
+                    }
+                }));
+    }
+
+    /**
+     * Determines if the given object was produced by a call to {@link #asInterfaceInstance asInterfaceInstance}.
+     * @param x any reference
+     * @return true if the reference is not null and points to an object produced by {@code asInterfaceInstance}
+     */
+    public static
+    boolean isWrapperInstance(Object x) {
+        return x instanceof WrapperInstance;
+    }
+
+    private static WrapperInstance asWrapperInstance(Object x) {
+        try {
+            if (x != null)
+                return (WrapperInstance) x;
+        } catch (ClassCastException ex) {
+        }
+        throw new IllegalArgumentException("not a wrapper instance");
+    }
+
+    /**
+     * Produces or recovers a target method handle which is behaviorally
+     * equivalent to the unique method of this wrapper instance.
+     * The object {@code x} must have been produced by a call to {@link #asInterfaceInstance asInterfaceInstance}.
+     * This requirement may be tested via {@link #isWrapperInstance isWrapperInstance}.
+     * @param x any reference
+     * @return a method handle implementing the unique method
+     * @throws IllegalArgumentException if the reference x is not to a wrapper instance
+     */
+    public static
+    MethodHandle wrapperInstanceTarget(Object x) {
+        return asWrapperInstance(x).getWrapperInstanceTarget();
+    }
+
+    /**
+     * Recovers the unique single-method interface type for which this wrapper instance was created.
+     * The object {@code x} must have been produced by a call to {@link #asInterfaceInstance asInterfaceInstance}.
+     * This requirement may be tested via {@link #isWrapperInstance isWrapperInstance}.
+     * @param x any reference
+     * @return the single-method interface type for which the wrapper was created
+     * @throws IllegalArgumentException if the reference x is not to a wrapper instance
+     */
+    public static
+    Class<?> wrapperInstanceType(Object x) {
+        return asWrapperInstance(x).getWrapperInstanceType();
+    }
+
+    private static
+    boolean isObjectMethod(Method m) {
+        switch (m.getName()) {
+        case "toString":
+            return (m.getReturnType() == String.class
+                    && m.getParameterTypes().length == 0);
+        case "hashCode":
+            return (m.getReturnType() == int.class
+                    && m.getParameterTypes().length == 0);
+        case "equals":
+            return (m.getReturnType() == boolean.class
+                    && m.getParameterTypes().length == 1
+                    && m.getParameterTypes()[0] == Object.class);
+        }
+        return false;
+    }
+
+    private static
+    Object callObjectMethod(Object self, Method m, Object[] args) {
+        assert(isObjectMethod(m)) : m;
+        switch (m.getName()) {
+        case "toString":
+            return self.getClass().getName() + "@" + Integer.toHexString(self.hashCode());
+        case "hashCode":
+            return System.identityHashCode(self);
+        case "equals":
+            return (self == args[0]);
+        }
+        return null;
+    }
+
+    private static
+    Method getSingleMethod(Class<?> intfc) {
+        if (!intfc.isInterface())  return null;
+        Method sm = null;
+        for (Method m : intfc.getMethods()) {
+            int mod = m.getModifiers();
+            if (Modifier.isAbstract(mod)) {
+                if (sm != null && !isObjectMethod(sm))
+                    return null;  // too many abstract methods
+                sm = m;
+            }
+        }
+        return sm;
+    }
+}