1 /*
2 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * - Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 *
11 * - Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * - Neither the name of Oracle nor the names of its
16 * contributors may be used to endorse or promote products derived
17 * from this software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
20 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
21 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
23 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
24 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
25 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
26 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
27 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
28 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
29 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 import java.lang.invoke.MethodHandle;
33 import java.lang.invoke.MethodHandles;
34 import java.lang.invoke.MethodType;
35 import java.util.ArrayList;
36 import java.util.List;
37 import jdk.dynalink.CallSiteDescriptor;
38 import jdk.dynalink.CompositeOperation;
39 import jdk.dynalink.NamedOperation;
40 import jdk.dynalink.Operation;
41 import jdk.dynalink.StandardOperation;
42 import jdk.dynalink.beans.BeansLinker;
43 import jdk.dynalink.linker.GuardingDynamicLinker;
44 import jdk.dynalink.linker.GuardingDynamicLinkerExporter;
45 import jdk.dynalink.linker.GuardedInvocation;
46 import jdk.dynalink.linker.TypeBasedGuardingDynamicLinker;
47 import jdk.dynalink.linker.LinkRequest;
48 import jdk.dynalink.linker.LinkerServices;
49 import jdk.dynalink.linker.support.Guards;
50 import jdk.dynalink.linker.support.Lookup;
51
52 /**
53 * This is a dynalink pluggable linker (see http://openjdk.java.net/jeps/276).
54 * This linker routes missing methods to Smalltalk-style doesNotUnderstand method.
55 * Object of any Java class that implements MissingMethodHandler is handled by this linker.
56 * For any method call, if a matching Java method is found, it is called. If there is no
57 * method by that name, then MissingMethodHandler.doesNotUnderstand is called.
58 */
59 public final class MissingMethodLinkerExporter extends GuardingDynamicLinkerExporter {
60 static {
61 System.out.println("pluggable dynalink missing method linker loaded");
62 }
63
64 // represents a MissingMethod - just stores as name and also serves a guard type
65 public static class MissingMethod {
66 private final String name;
67
68 public MissingMethod(String name) {
69 this.name = name;
70 }
71
72 public String getName() {
73 return name;
74 }
75 }
76
77 // MissingMethodHandler.doesNotUnderstand method
78 private static final MethodHandle DOES_NOT_UNDERSTAND;
79
80 // type of MissingMethodHandler - but "this" and String args are flipped
81 private static final MethodType FLIPPED_DOES_NOT_UNDERSTAND_TYPE;
82
83 // "is this a MissingMethod?" guard
84 private static final MethodHandle IS_MISSING_METHOD;
85
86 // MissingMethod object->it's name filter
87 private static final MethodHandle MISSING_METHOD_TO_NAME;
88
89 static {
90 DOES_NOT_UNDERSTAND = Lookup.PUBLIC.findVirtual(
91 MissingMethodHandler.class,
92 "doesNotUnderstand",
93 MethodType.methodType(Object.class, String.class, Object[].class));
94 FLIPPED_DOES_NOT_UNDERSTAND_TYPE =
95 MethodType.methodType(Object.class, String.class, MissingMethodHandler.class, Object[].class);
96 IS_MISSING_METHOD = Guards.isOfClass(MissingMethod.class,
97 MethodType.methodType(Boolean.TYPE, Object.class));
98 MISSING_METHOD_TO_NAME = Lookup.PUBLIC.findVirtual(MissingMethod.class,
99 "getName", MethodType.methodType(String.class));
100 }
101
102 // locate the first standard operation from the call descriptor
103 private static StandardOperation getFirstStandardOperation(final CallSiteDescriptor desc) {
104 final Operation base = NamedOperation.getBaseOperation(desc.getOperation());
105 if (base instanceof StandardOperation) {
106 return (StandardOperation)base;
107 } else if (base instanceof CompositeOperation) {
108 final CompositeOperation cop = (CompositeOperation)base;
109 for(int i = 0; i < cop.getOperationCount(); ++i) {
110 final Operation op = cop.getOperation(i);
111 if (op instanceof StandardOperation) {
112 return (StandardOperation)op;
113 }
114 }
115 }
116 return null;
117 }
118
119 @Override
120 public List<GuardingDynamicLinker> get() {
121 final ArrayList<GuardingDynamicLinker> linkers = new ArrayList<>();
122 final BeansLinker beansLinker = new BeansLinker();
123 linkers.add(new TypeBasedGuardingDynamicLinker() {
124 // only handles MissingMethodHandler and MissingMethod objects
125 @Override
126 public boolean canLinkType(final Class<?> type) {
127 return
128 MissingMethodHandler.class.isAssignableFrom(type) ||
129 type == MissingMethod.class;
130 }
131
132 @Override
133 public GuardedInvocation getGuardedInvocation(LinkRequest request,
134 LinkerServices linkerServices) throws Exception {
135 final Object self = request.getReceiver();
136 CallSiteDescriptor desc = request.getCallSiteDescriptor();
137
138 // any method call is done by two steps. Step (1) GET_METHOD and (2) is CALL
139 // For step (1), we check if GET_METHOD can succeed by Java linker, if so
140 // we return that method object. If not, we return a MissingMethod object.
141 if (self instanceof MissingMethodHandler) {
142 // Check if this is a named GET_METHOD first.
143 boolean isGetMethod = getFirstStandardOperation(desc) == StandardOperation.GET_METHOD;
144 Object name = NamedOperation.getName(desc.getOperation());
145 if (isGetMethod && name instanceof String) {
146 GuardingDynamicLinker javaLinker = beansLinker.getLinkerForClass(self.getClass());
147 GuardedInvocation inv;
148 try {
149 inv = javaLinker.getGuardedInvocation(request, linkerServices);
150 } catch (final Throwable th) {
151 inv = null;
152 }
153
154 String nameStr = name.toString();
155 if (inv == null) {
156 // use "this" for just guard and drop it -- return a constant Method handle
157 // that returns a newly created MissingMethod object
158 MethodHandle mh = MethodHandles.constant(Object.class, new MissingMethod(nameStr));
159 inv = new GuardedInvocation(
160 MethodHandles.dropArguments(mh, 0, Object.class),
161 Guards.isOfClass(self.getClass(), MethodType.methodType(Boolean.TYPE, Object.class)));
162 }
163
164 return inv;
165 }
166 } else if (self instanceof MissingMethod) {
167 // This is step (2). We call MissingMethodHandler.doesNotUnderstand here
168 // Check if this is this a CALL first.
169 boolean isCall = getFirstStandardOperation(desc) == StandardOperation.CALL;
170 if (isCall) {
171 MethodHandle mh = DOES_NOT_UNDERSTAND;
172
173 // flip "this" and method name (String)
174 mh = MethodHandles.permuteArguments(mh, FLIPPED_DOES_NOT_UNDERSTAND_TYPE, 1, 0, 2);
175
176 // collect rest of the arguments as vararg
177 mh = mh.asCollector(Object[].class, desc.getMethodType().parameterCount() - 2);
178
179 // convert MissingMethod object to it's name
180 mh = MethodHandles.filterArguments(mh, 0, MISSING_METHOD_TO_NAME);
181 return new GuardedInvocation(mh, IS_MISSING_METHOD);
182 }
183 }
184
185 return null;
186 }
187 });
188 return linkers;
189 }
190 }