179 lines
8.4 KiB
Java
179 lines
8.4 KiB
Java
/*
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* Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* - Neither the name of Oracle nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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import java.lang.invoke.MethodHandle;
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import java.lang.invoke.MethodHandles;
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import java.lang.invoke.MethodType;
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import java.util.ArrayList;
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import java.util.List;
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import jdk.dynalink.CallSiteDescriptor;
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import jdk.dynalink.NamedOperation;
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import jdk.dynalink.NamespaceOperation;
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import jdk.dynalink.Operation;
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import jdk.dynalink.StandardNamespace;
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import jdk.dynalink.StandardOperation;
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import jdk.dynalink.beans.BeansLinker;
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import jdk.dynalink.linker.GuardedInvocation;
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import jdk.dynalink.linker.GuardingDynamicLinker;
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import jdk.dynalink.linker.GuardingDynamicLinkerExporter;
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import jdk.dynalink.linker.LinkRequest;
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import jdk.dynalink.linker.LinkerServices;
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import jdk.dynalink.linker.TypeBasedGuardingDynamicLinker;
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import jdk.dynalink.linker.support.Guards;
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import jdk.dynalink.linker.support.Lookup;
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/**
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* This is a dynalink pluggable linker (see http://openjdk.java.net/jeps/276).
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* This linker routes missing methods to Smalltalk-style doesNotUnderstand method.
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* Object of any Java class that implements MissingMethodHandler is handled by this linker.
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* For any method call, if a matching Java method is found, it is called. If there is no
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* method by that name, then MissingMethodHandler.doesNotUnderstand is called.
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*/
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public final class MissingMethodLinkerExporter extends GuardingDynamicLinkerExporter {
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static {
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System.out.println("pluggable dynalink missing method linker loaded");
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}
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// represents a MissingMethod - just stores as name and also serves a guard type
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public static class MissingMethod {
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private final String name;
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public MissingMethod(final String name) {
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this.name = name;
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}
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public String getName() {
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return name;
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}
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}
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// MissingMethodHandler.doesNotUnderstand method
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private static final MethodHandle DOES_NOT_UNDERSTAND;
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// type of MissingMethodHandler - but "this" and String args are flipped
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private static final MethodType FLIPPED_DOES_NOT_UNDERSTAND_TYPE;
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// "is this a MissingMethod?" guard
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private static final MethodHandle IS_MISSING_METHOD;
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// MissingMethod object->it's name filter
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private static final MethodHandle MISSING_METHOD_TO_NAME;
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static {
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DOES_NOT_UNDERSTAND = Lookup.PUBLIC.findVirtual(
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MissingMethodHandler.class,
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"doesNotUnderstand",
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MethodType.methodType(Object.class, String.class, Object[].class));
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FLIPPED_DOES_NOT_UNDERSTAND_TYPE =
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MethodType.methodType(Object.class, String.class, MissingMethodHandler.class, Object[].class);
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IS_MISSING_METHOD = Guards.isOfClass(MissingMethod.class,
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MethodType.methodType(Boolean.TYPE, Object.class));
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MISSING_METHOD_TO_NAME = Lookup.PUBLIC.findVirtual(MissingMethod.class,
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"getName", MethodType.methodType(String.class));
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}
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@Override
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public List<GuardingDynamicLinker> get() {
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final ArrayList<GuardingDynamicLinker> linkers = new ArrayList<>();
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final BeansLinker beansLinker = new BeansLinker();
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linkers.add(new TypeBasedGuardingDynamicLinker() {
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// only handles MissingMethodHandler and MissingMethod objects
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@Override
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public boolean canLinkType(final Class<?> type) {
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return
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MissingMethodHandler.class.isAssignableFrom(type) ||
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type == MissingMethod.class;
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}
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@Override
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public GuardedInvocation getGuardedInvocation(final LinkRequest request,
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final LinkerServices linkerServices) throws Exception {
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final Object self = request.getReceiver();
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final CallSiteDescriptor desc = request.getCallSiteDescriptor();
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// any method call is done by two steps. Step (1) GET_METHOD and (2) is CALL
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// For step (1), we check if GET_METHOD can succeed by Java linker, if so
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// we return that method object. If not, we return a MissingMethod object.
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if (self instanceof MissingMethodHandler) {
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// Check if this is a named GET_METHOD first.
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final Operation namedOp = desc.getOperation();
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final Operation namespaceOp = NamedOperation.getBaseOperation(namedOp);
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final Operation op = NamespaceOperation.getBaseOperation(namespaceOp);
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final boolean isGetMethod = op == StandardOperation.GET && StandardNamespace.findFirst(namespaceOp) == StandardNamespace.METHOD;
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final Object name = NamedOperation.getName(namedOp);
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if (isGetMethod && name instanceof String) {
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final GuardingDynamicLinker javaLinker = beansLinker.getLinkerForClass(self.getClass());
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GuardedInvocation inv;
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try {
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inv = javaLinker.getGuardedInvocation(request, linkerServices);
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} catch (final Throwable th) {
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inv = null;
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}
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final String nameStr = name.toString();
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if (inv == null) {
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// use "this" for just guard and drop it -- return a constant Method handle
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// that returns a newly created MissingMethod object
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final MethodHandle mh = MethodHandles.constant(Object.class, new MissingMethod(nameStr));
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inv = new GuardedInvocation(
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MethodHandles.dropArguments(mh, 0, Object.class),
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Guards.isOfClass(self.getClass(), MethodType.methodType(Boolean.TYPE, Object.class)));
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}
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return inv;
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}
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} else if (self instanceof MissingMethod) {
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// This is step (2). We call MissingMethodHandler.doesNotUnderstand here
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// Check if this is this a CALL first.
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final boolean isCall = NamedOperation.getBaseOperation(desc.getOperation()) == StandardOperation.CALL;
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if (isCall) {
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MethodHandle mh = DOES_NOT_UNDERSTAND;
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// flip "this" and method name (String)
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mh = MethodHandles.permuteArguments(mh, FLIPPED_DOES_NOT_UNDERSTAND_TYPE, 1, 0, 2);
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// collect rest of the arguments as vararg
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mh = mh.asCollector(Object[].class, desc.getMethodType().parameterCount() - 2);
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// convert MissingMethod object to it's name
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mh = MethodHandles.filterArguments(mh, 0, MISSING_METHOD_TO_NAME);
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return new GuardedInvocation(mh, IS_MISSING_METHOD);
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}
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}
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return null;
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}
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});
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return linkers;
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}
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}
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