diff -r 000000000000 -r c880a8a8803b rt/emul/compact/src/main/java/java/lang/invoke/MethodHandleProxies.java --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/rt/emul/compact/src/main/java/java/lang/invoke/MethodHandleProxies.java Sat Aug 09 11:11:13 2014 +0200 @@ -0,0 +1,321 @@ +/* + * Copyright (c) 2008, 2013, 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 java.security.AccessController; +import java.security.PrivilegedAction; +import sun.invoke.WrapperInstance; +import java.util.ArrayList; +import sun.reflect.CallerSensitive; +import sun.reflect.Reflection; +import sun.reflect.misc.ReflectUtil; + +/** + * 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. + *

+ * 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. + *

+ * The interface must be public. No additional access checks are performed. + *

+ * 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}. + *

+ * 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. + *

+ * 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. + *

+ * Implementation Note: + * 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}. + *

+ * The method handle may throw an undeclared exception, + * 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. + *

+ * 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. + *

+ * 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. + *

+ * 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. + *

+ * If a security manager is installed, this method is caller sensitive. + * During any invocation of the target method handle via the returned wrapper, + * the original creator of the wrapper (the caller) will be visible + * to context checks requested by the security manager. + * + * @param the desired type of the wrapper, a single-method interface + * @param intfc a class object representing {@code T} + * @param target the method handle to invoke from the wrapper + * @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: + //

+ // 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. + //

+ // 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. + //

+ // 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. + // + @CallerSensitive + public static + T asInterfaceInstance(final Class intfc, final MethodHandle target) { + if (!intfc.isInterface() || !Modifier.isPublic(intfc.getModifiers())) + throw new IllegalArgumentException("not a public interface: "+intfc.getName()); + final MethodHandle mh; + if (System.getSecurityManager() != null) { + final Class caller = Reflection.getCallerClass(); + final ClassLoader ccl = caller != null ? caller.getClassLoader() : null; + ReflectUtil.checkProxyPackageAccess(ccl, intfc); + mh = ccl != null ? bindCaller(target, caller) : target; + } else { + mh = target; + } + ClassLoader proxyLoader = intfc.getClassLoader(); + if (proxyLoader == null) { + ClassLoader cl = Thread.currentThread().getContextClassLoader(); // avoid use of BCP + proxyLoader = cl != null ? cl : ClassLoader.getSystemClassLoader(); + } + final Method[] methods = getSingleNameMethods(intfc); + if (methods == null) + throw new IllegalArgumentException("not a single-method interface: "+intfc.getName()); + final MethodHandle[] vaTargets = new MethodHandle[methods.length]; + for (int i = 0; i < methods.length; i++) { + Method sm = methods[i]; + MethodType smMT = MethodType.methodType(sm.getReturnType(), sm.getParameterTypes()); + MethodHandle checkTarget = mh.asType(smMT); // make throw WMT + checkTarget = checkTarget.asType(checkTarget.type().changeReturnType(Object.class)); + vaTargets[i] = checkTarget.asSpreader(Object[].class, smMT.parameterCount()); + } + final InvocationHandler ih = 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 { + for (int i = 0; i < methods.length; i++) { + if (method.equals(methods[i])) + return vaTargets[i].invokeExact(args); + } + if (method.getDeclaringClass() == WrapperInstance.class) + return getArg(method.getName()); + if (isObjectMethod(method)) + return callObjectMethod(proxy, method, args); + throw new InternalError("bad proxy method: "+method); + } + }; + + final Object proxy; + if (System.getSecurityManager() != null) { + // sun.invoke.WrapperInstance is a restricted interface not accessible + // by any non-null class loader. + final ClassLoader loader = proxyLoader; + proxy = AccessController.doPrivileged(new PrivilegedAction() { + public Object run() { + return Proxy.newProxyInstance( + loader, + new Class[]{ intfc, WrapperInstance.class }, + ih); + } + }); + } else { + proxy = Proxy.newProxyInstance(proxyLoader, + new Class[]{ intfc, WrapperInstance.class }, + ih); + } + return intfc.cast(proxy); + } + + private static MethodHandle bindCaller(MethodHandle target, Class hostClass) { + MethodHandle cbmh = MethodHandleImpl.bindCaller(target, hostClass); + if (target.isVarargsCollector()) { + MethodType type = cbmh.type(); + int arity = type.parameterCount(); + return cbmh.asVarargsCollector(type.parameterType(arity-1)); + } + return cbmh; + } + + /** + * 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[] getSingleNameMethods(Class intfc) { + ArrayList methods = new ArrayList(); + String uniqueName = null; + for (Method m : intfc.getMethods()) { + if (isObjectMethod(m)) continue; + if (!Modifier.isAbstract(m.getModifiers())) continue; + String mname = m.getName(); + if (uniqueName == null) + uniqueName = mname; + else if (!uniqueName.equals(mname)) + return null; // too many abstract methods + methods.add(m); + } + if (uniqueName == null) return null; + return methods.toArray(new Method[methods.size()]); + } +}