48826
|
1 |
/*
|
|
2 |
* Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
|
|
3 |
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
|
|
4 |
*
|
|
5 |
* This code is free software; you can redistribute it and/or modify it
|
|
6 |
* under the terms of the GNU General Public License version 2 only, as
|
|
7 |
* published by the Free Software Foundation. Oracle designates this
|
|
8 |
* particular file as subject to the "Classpath" exception as provided
|
|
9 |
* by Oracle in the LICENSE file that accompanied this code.
|
|
10 |
*
|
|
11 |
* This code is distributed in the hope that it will be useful, but WITHOUT
|
|
12 |
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
|
13 |
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
|
|
14 |
* version 2 for more details (a copy is included in the LICENSE file that
|
|
15 |
* accompanied this code).
|
|
16 |
*
|
|
17 |
* You should have received a copy of the GNU General Public License version
|
|
18 |
* 2 along with this work; if not, write to the Free Software Foundation,
|
|
19 |
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
|
|
20 |
*
|
|
21 |
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
|
|
22 |
* or visit www.oracle.com if you need additional information or have any
|
|
23 |
* questions.
|
|
24 |
*/
|
|
25 |
|
|
26 |
package java.lang.invoke;
|
|
27 |
|
|
28 |
import java.lang.invoke.MethodHandles.Lookup;
|
|
29 |
|
|
30 |
/**
|
|
31 |
* An interface providing full static information about a particular
|
|
32 |
* call to a
|
|
33 |
* <a href="package-summary.html#bsm">bootstrap method</a> of an
|
|
34 |
* dynamic call site or dynamic constant.
|
|
35 |
* This information includes the method itself, the associated
|
|
36 |
* name and type, and any associated static arguments.
|
|
37 |
* <p>
|
|
38 |
* If a bootstrap method declares exactly two arguments, and is
|
|
39 |
* not of variable arity, then it is fed only two arguments by
|
|
40 |
* the JVM, the {@linkplain Lookup lookup object} and an instance
|
|
41 |
* of {@code BootstrapCallInfo} which supplies the rest of the
|
|
42 |
* information about the call.
|
|
43 |
* <p>
|
|
44 |
* The API for accessing the static arguments allows the bootstrap
|
|
45 |
* method to reorder the resolution (in the constant pool) of the
|
|
46 |
* static arguments, and to catch errors resulting from the resolution.
|
|
47 |
* This mode of evaluation <em>pulls</em> bootstrap parameters from
|
|
48 |
* the JVM under control of the bootstrap method, as opposed to
|
|
49 |
* the JVM <em>pushing</em> parameters to a bootstrap method
|
|
50 |
* by resolving them all before the bootstrap method is called.
|
|
51 |
* @apiNote
|
|
52 |
* <p>
|
|
53 |
* The {@linkplain Lookup lookup object} is <em>not</em> included in this
|
|
54 |
* bundle of information, so as not to obscure the access control
|
|
55 |
* logic of the program.
|
|
56 |
* In cases where there are many thousands of parameters, it may
|
|
57 |
* be preferable to pull their resolved values, either singly or in
|
|
58 |
* batches, rather than wait until all of them have been resolved
|
|
59 |
* before a constant or call site can be used.
|
|
60 |
* <p>
|
|
61 |
* A push mode bootstrap method can be adapted to a pull mode
|
|
62 |
* bootstrap method, and vice versa. For example, this generic
|
|
63 |
* adapter pops a push-mode bootstrap method from the beginning
|
|
64 |
* of the static argument list, eagerly resolves all the remaining
|
|
65 |
* static arguments, and invokes the popped method in push mode.
|
|
66 |
* The callee has no way of telling that it was not called directly
|
|
67 |
* from the JVM.
|
|
68 |
* <blockquote><pre>{@code
|
|
69 |
static Object genericBSM(Lookup lookup, BootstrapCallInfo<Object> bsci)
|
|
70 |
throws Throwable {
|
|
71 |
ArrayList<Object> args = new ArrayList<>();
|
|
72 |
args.add(lookup);
|
|
73 |
args.add(bsci.invocationName());
|
|
74 |
args.add(bsci.invocationType());
|
|
75 |
MethodHandle bsm = (MethodHandle) bsci.get(0);
|
|
76 |
List<Object> restOfArgs = bsci.asList().subList(1, bsci.size();
|
|
77 |
// the next line eagerly resolves all remaining static arguments:
|
|
78 |
args.addAll(restOfArgs);
|
|
79 |
return bsm.invokeWithArguments(args);
|
|
80 |
}
|
|
81 |
* }</pre></blockquote>
|
|
82 |
*
|
|
83 |
* <p>
|
|
84 |
* In the other direction, here is a combinator which pops
|
|
85 |
* a pull-mode bootstrap method from the beginning of a list of
|
|
86 |
* static argument values (already resolved), reformats all of
|
|
87 |
* the arguments into a pair of a lookup and a {@code BootstrapCallInfo},
|
|
88 |
* and invokes the popped method. Again the callee has no way of
|
|
89 |
* telling it was not called directly by the JVM, except that
|
|
90 |
* all of the constant values will appear as resolved.
|
|
91 |
* Put another way, if any constant fails to resolve, the
|
|
92 |
* callee will not be able to catch the resulting error,
|
|
93 |
* since the error will be thrown by the JVM before the
|
|
94 |
* bootstrap method is entered.
|
|
95 |
* <blockquote><pre>{@code
|
|
96 |
static Object genericBSM(Lookup lookup, String name, Object type,
|
|
97 |
MethodHandle bsm, Object... args)
|
|
98 |
throws Throwable {
|
|
99 |
ConstantGroup cons = ConstantGroup.makeConstantGroup(Arrays.asList(args));
|
|
100 |
BootstrapCallInfo<Object> bsci = makeBootstrapCallInfo(bsm, name, type, cons);
|
|
101 |
return bsm.invoke(lookup, bsci);
|
|
102 |
}
|
|
103 |
* }</pre></blockquote>
|
|
104 |
*
|
|
105 |
* @since 1.10
|
|
106 |
*/
|
|
107 |
// public
|
|
108 |
interface BootstrapCallInfo<T> extends ConstantGroup {
|
|
109 |
/** Returns the bootstrap method for this call.
|
|
110 |
* @return the bootstrap method
|
|
111 |
*/
|
|
112 |
MethodHandle bootstrapMethod();
|
|
113 |
|
|
114 |
/** Returns the method name or constant name for this call.
|
|
115 |
* @return the method name or constant name
|
|
116 |
*/
|
|
117 |
String invocationName();
|
|
118 |
|
|
119 |
/** Returns the method type or constant type for this call.
|
|
120 |
* @return the method type or constant type
|
|
121 |
*/
|
|
122 |
T invocationType();
|
|
123 |
|
|
124 |
/**
|
|
125 |
* Make a new bootstrap call descriptor with the given components.
|
|
126 |
* @param bsm bootstrap method
|
|
127 |
* @param name invocation name
|
|
128 |
* @param type invocation type
|
|
129 |
* @param constants the additional static arguments for the bootstrap method
|
|
130 |
* @param <T> the type of the invocation type, either {@link MethodHandle} or {@link Class}
|
|
131 |
* @return a new bootstrap call descriptor with the given components
|
|
132 |
*/
|
|
133 |
static <T> BootstrapCallInfo<T> makeBootstrapCallInfo(MethodHandle bsm,
|
|
134 |
String name,
|
|
135 |
T type,
|
|
136 |
ConstantGroup constants) {
|
|
137 |
AbstractConstantGroup.BSCIWithCache<T> bsci = new AbstractConstantGroup.BSCIWithCache<>(bsm, name, type, constants.size());
|
|
138 |
final Object NP = AbstractConstantGroup.BSCIWithCache.NOT_PRESENT;
|
|
139 |
bsci.initializeCache(constants.asList(NP), NP);
|
|
140 |
return bsci;
|
|
141 |
}
|
|
142 |
}
|