1 /*
2 * Copyright (c) 2014, 2016, 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 *
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23 * questions.
24 */
25
26 package java.lang.module;
27
28 import java.io.PrintStream;
29 import java.util.ArrayDeque;
30 import java.util.ArrayList;
31 import java.util.Collection;
32 import java.util.Collections;
33 import java.util.Deque;
34 import java.util.HashSet;
35 import java.util.List;
36 import java.util.Map;
37 import java.util.Map.Entry;
38 import java.util.Objects;
39 import java.util.Optional;
40 import java.util.Set;
41 import java.util.stream.Collectors;
42 import java.util.stream.Stream;
43
44 /**
45 * The configuration that is the result of resolution or resolution with
46 * service binding.
47 *
48 * <h2><a name="resolution">Resolution</a></h2>
49 *
50 * <p> Resolution is the process of computing the transitive closure of a set
51 * of root modules over a set of observable modules by resolving the
52 * dependences expressed by {@code requires} clauses.
53 *
54 * The <em>dependence graph</em> is augmented with edges that take account of
55 * implicitly declared dependences ({@code requires transitive}) to create a
56 * <em>readability graph</em>. A {@code Configuration} encapsulates the
57 * resulting graph of {@link ResolvedModule resolved modules}.
58 *
59 * <p> Suppose we have the following observable modules: </p>
60 * <pre> {@code
61 * module m1 { requires m2; }
62 * module m2 { requires transitive m3; }
63 * module m3 { }
64 * module m4 { }
65 * } </pre>
66 *
67 * <p> If the module {@code m1} is resolved then the resulting configuration
68 * contains three modules ({@code m1}, {@code m2}, {@code m3}). The edges in
69 * its readability graph are: </p>
70 * <pre> {@code
71 * m1 --> m2 (meaning m1 reads m2)
72 * m1 --> m3
73 * m2 --> m3
74 * } </pre>
75 *
76 * <p> Resolution is an additive process. When computing the transitive closure
77 * then the dependence relation may include dependences on modules in parent
78 * configurations. The result is a <em>relative configuration</em> that is
79 * relative to one or more parent configurations and where the readability graph
80 * may have edges from modules in the configuration to modules in parent
81 * configurations.
82 *
83 * </p>
84 *
85 * <p> Suppose we have the following observable modules: </p>
86 * <pre> {@code
87 * module m1 { requires m2; requires java.xml; }
88 * module m2 { }
89 * } </pre>
90 *
91 * <p> If module {@code m1} is resolved with the configuration for the {@link
92 * java.lang.reflect.Layer#boot() boot} layer as the parent then the resulting
93 * configuration contains two modules ({@code m1}, {@code m2}). The edges in
94 * its readability graph are:
95 * <pre> {@code
96 * m1 --> m2
97 * m1 --> java.xml
98 * } </pre>
99 * where module {@code java.xml} is in the parent configuration. For
100 * simplicity, this example omits the implicitly declared dependence on the
101 * {@code java.base} module.
102 *
103 * <a name="automaticmoduleresolution"></a>
104 * <p> {@link ModuleDescriptor#isAutomatic() Automatic} modules receive special
105 * treatment during resolution. Each automatic module is resolved so that it
106 * reads all other modules in the configuration and all parent configurations.
107 * Each automatic module is also resolved as if it {@code requires transitive}
108 * all other automatic modules in the configuration (and all automatic modules
109 * in parent configurations). </p>
110
111 * <h2><a name="servicebinding">Service binding</a></h2>
112 *
113 * <p> Service binding is the process of augmenting a graph of resolved modules
114 * from the set of observable modules induced by the service-use dependence
115 * ({@code uses} and {@code provides} clauses). Any module that was not
116 * previously in the graph requires resolution to compute its transitive
117 * closure. Service binding is an iterative process in that adding a module
118 * that satisfies some service-use dependence may introduce new service-use
119 * dependences. </p>
120 *
121 * <p> Suppose we have the following observable modules: </p>
122 * <pre> {@code
123 * module m1 { exports p; uses p.S; }
124 * module m2 { requires m1; provides p.S with p2.S2; }
125 * module m3 { requires m1; requires m4; provides p.S with p3.S3; }
126 * module m4 { }
127 * } </pre>
128 *
129 * <p> If the module {@code m1} is resolved then the resulting graph of modules
130 * has one module ({@code m1}). If the graph is augmented with modules induced
131 * by the service-use dependence relation then the configuration will contain
132 * four modules ({@code m1}, {@code m2}, {@code m3}, {@code m4}). The edges in
133 * its readability graph are: </p>
134 * <pre> {@code
135 * m2 --> m1
136 * m3 --> m1
137 * m3 --> m4
138 * } </pre>
139 * <p> The edges in the conceptual service-use graph are: </p>
140 * <pre> {@code
141 * m1 --> m2 (meaning m1 uses a service that is provided by m2)
142 * m1 --> m3
143 * } </pre>
144 *
145 * <p> If this configuration is instantiated as a {@code Layer}, and if code in
146 * module {@code m1} uses {@link java.util.ServiceLoader ServiceLoader} to
147 * iterate over implementations of {@code p.S.class}, then it will iterate over
148 * an instance of {@code p2.S2} and {@code p3.S3}. </p>
149 *
150 * <h3> Example </h3>
151 *
152 * <p> The following example uses the {@code resolveRequires} method to resolve
153 * a module named <em>myapp</em> with the configuration for the boot layer as
154 * the parent configuration. It prints the name of each resolved module and
155 * the names of the modules that each module reads. </p>
156 *
157 * <pre>{@code
158 * ModuleFinder finder = ModuleFinder.of(dir1, dir2, dir3);
159 *
160 * Configuration parent = Layer.boot().configuration();
161 *
162 * Configuration cf = parent.resolveRequires(finder,
163 * ModuleFinder.of(),
164 * Set.of("myapp"));
165 * cf.modules().forEach(m -> {
166 * System.out.format("%s -> %s%n",
167 * m.name(),
168 * m.reads().stream()
169 * .map(ResolvedModule::name)
170 * .collect(Collectors.joining(", ")));
171 * });
172 * }</pre>
173 *
174 * @since 9
175 * @see java.lang.reflect.Layer
176 */
177 public final class Configuration {
178
179 // @see Configuration#empty()
180 private static final Configuration EMPTY_CONFIGURATION = new Configuration();
181
182 // parent configurations, in search order
183 private final List<Configuration> parents;
184
185 private final Map<ResolvedModule, Set<ResolvedModule>> graph;
186 private final Set<ResolvedModule> modules;
187 private final Map<String, ResolvedModule> nameToModule;
188
189 private Configuration() {
190 this.parents = Collections.emptyList();
191 this.graph = Collections.emptyMap();
192 this.modules = Collections.emptySet();
193 this.nameToModule = Collections.emptyMap();
194 }
195
196 private Configuration(List<Configuration> parents,
197 Resolver resolver,
198 boolean check)
199 {
200 Map<ResolvedModule, Set<ResolvedModule>> g = resolver.finish(this, check);
201
202 @SuppressWarnings(value = {"rawtypes", "unchecked"})
203 Entry<String, ResolvedModule>[] nameEntries
204 = (Entry<String, ResolvedModule>[])new Entry[g.size()];
205 ResolvedModule[] moduleArray = new ResolvedModule[g.size()];
206 int i = 0;
207 for (ResolvedModule resolvedModule : g.keySet()) {
208 moduleArray[i] = resolvedModule;
209 nameEntries[i] = Map.entry(resolvedModule.name(), resolvedModule);
210 i++;
211 }
212
213 this.parents = Collections.unmodifiableList(parents);
214 this.graph = g;
215 this.modules = Set.of(moduleArray);
216 this.nameToModule = Map.ofEntries(nameEntries);
217 }
218
219
220 /**
221 * Resolves a collection of root modules, with this configuration as its
222 * parent, to create a new configuration. This method works exactly as
223 * specified by the static {@link
224 * #resolveRequires(ModuleFinder,List,ModuleFinder,Collection) resolveRequires}
225 * method when invoked with this configuration as the parent. In other words,
226 * if this configuration is {@code cf} then this method is equivalent to
227 * invoking:
228 * <pre> {@code
229 * Configuration.resolveRequires(before, List.of(cf), after, roots);
230 * }</pre>
231 *
232 * @param before
233 * The <em>before</em> module finder to find modules
234 * @param after
235 * The <em>after</em> module finder to locate modules when a
236 * module cannot be located by the {@code before} module finder
237 * and the module is not in this configuration
238 * @param roots
239 * The possibly-empty collection of module names of the modules
240 * to resolve
241 *
242 * @return The configuration that is the result of resolving the given
243 * root modules
244 *
245 * @throws ResolutionException
246 * If resolution or the post-resolution checks fail
247 * @throws SecurityException
248 * If locating a module is denied by the security manager
249 */
250 public Configuration resolveRequires(ModuleFinder before,
251 ModuleFinder after,
252 Collection<String> roots)
253 {
254 return resolveRequires(before, List.of(this), after, roots);
255 }
256
257
258 /**
259 * Resolves a collection of root modules, with service binding, and with
260 * this configuration as its parent, to create a new configuration.
261 * This method works exactly as specified by the static {@link
262 * #resolveRequiresAndUses(ModuleFinder,List,ModuleFinder,Collection)
263 * resolveRequiresAndUses} method when invoked with this configuration
264 * as the parent. In other words, if this configuration is {@code cf} then
265 * this method is equivalent to invoking:
266 * <pre> {@code
267 * Configuration.resolveRequiresAndUses(before, List.of(cf), after, roots);
268 * }</pre>
269 *
270 *
271 * @param before
272 * The <em>before</em> module finder to find modules
273 * @param after
274 * The <em>after</em> module finder to locate modules when not
275 * located by the {@code before} module finder and this
276 * configuration
277 * @param roots
278 * The possibly-empty collection of module names of the modules
279 * to resolve
280 *
281 * @return The configuration that is the result of resolving the given
282 * root modules
283 *
284 * @throws ResolutionException
285 * If resolution or the post-resolution checks fail
286 * @throws SecurityException
287 * If locating a module is denied by the security manager
288 */
289 public Configuration resolveRequiresAndUses(ModuleFinder before,
290 ModuleFinder after,
291 Collection<String> roots)
292 {
293 return resolveRequiresAndUses(before, List.of(this), after, roots);
294 }
295
296
297 /**
298 * Resolves a collection of root modules, with service binding, and with
299 * the empty configuration as its parent. The post resolution checks
300 * are optionally run.
301 *
302 * This method is used to create the configuration for the boot layer.
303 */
304 static Configuration resolveRequiresAndUses(ModuleFinder finder,
305 Collection<String> roots,
306 boolean check,
307 PrintStream traceOutput)
308 {
309 List<Configuration> parents = List.of(empty());
310 Resolver resolver = new Resolver(finder, parents, ModuleFinder.of(), traceOutput);
311 resolver.resolveRequires(roots).resolveUses();
312
313 return new Configuration(parents, resolver, check);
314 }
315
316
317 /**
318 * Resolves a collection of root modules to create a configuration.
319 *
320 * <p> Each root module is located using the given {@code before} module
321 * finder. If a module is not found then it is located in the parent
322 * configuration as if by invoking the {@link #findModule(String)
323 * findModule} method on each parent in iteration order. If not found then
324 * the module is located using the given {@code after} module finder. The
325 * same search order is used to locate transitive dependences. Root modules
326 * or dependences that are located in a parent configuration are resolved
327 * no further and are not included in the resulting configuration. </p>
328 *
329 * <p> When all modules have been resolved then the resulting dependency
330 * graph is checked to ensure that it does not contain cycles. A
331 * readability graph is constructed and in conjunction with the module
332 * exports and service use, checked for consistency. </p>
333 *
334 * <p> Resolution and the (post-resolution) consistency checks may fail for
335 * following reasons: </p>
336 *
337 * <ul>
338 * <li><p> A root module, or a direct or transitive dependency, is not
339 * found. </p></li>
340 *
341 * <li><p> An error occurs when attempting to find a module.
342 * Possible errors include I/O errors, errors detected parsing a module
343 * descriptor ({@code module-info.class}) or two versions of the same
344 * module are found in the same directory. </p></li>
345 *
346 * <li><p> A cycle is detected, say where module {@code m1} requires
347 * module {@code m2} and {@code m2} requires {@code m1}. </p></li>
348 *
349 * <li><p> Two or more modules in the configuration export the same
350 * package to a module that reads both. This includes the case where a
351 * module {@code M} containing package {@code p} reads another module
352 * that exports {@code p} to {@code M}. </p></li>
353 *
354 * <li><p> A module {@code M} declares that it "{@code uses p.S}" or
355 * "{@code provides p.S with ...}" but package {@code p} is neither in
356 * module {@code M} nor exported to {@code M} by any module that
357 * {@code M} reads. </p></li>
358 *
359 * <li><p> A module {@code M} declares that it
360 * "{@code provides ... with q.T}" but package {@code q} is not in
361 * module {@code M}. </p></li>
362 *
363 * <li><p> Two or more modules in the configuration are specific to
364 * different {@link ModuleDescriptor#osName() operating systems},
365 * {@link ModuleDescriptor#osArch() architectures}, or {@link
366 * ModuleDescriptor#osVersion() versions}. </p></li>
367 *
368 * <li><p> Other implementation specific checks, for example referential
369 * integrity checks to ensure that different versions of tighly coupled
370 * modules cannot be combined in the same configuration. </p></li>
371 *
372 * </ul>
373 *
374 * @param before
375 * The <em>before</em> module finder to find modules
376 * @param parents
377 * The list parent configurations in search order
378 * @param after
379 * The <em>after</em> module finder to locate modules when not
380 * located by the {@code before} module finder or in parent
381 * configurations
382 * @param roots
383 * The possibly-empty collection of module names of the modules
384 * to resolve
385 *
386 * @return The configuration that is the result of resolving the given
387 * root modules
388 *
389 * @throws ResolutionException
390 * If resolution or the post-resolution checks fail
391 * @throws IllegalArgumentException
392 * If the list of parents is empty
393 * @throws SecurityException
394 * If locating a module is denied by the security manager
395 */
396 public static Configuration resolveRequires(ModuleFinder before,
397 List<Configuration> parents,
398 ModuleFinder after,
399 Collection<String> roots)
400 {
401 Objects.requireNonNull(before);
402 Objects.requireNonNull(after);
403 Objects.requireNonNull(roots);
404
405 List<Configuration> parentList = new ArrayList<>(parents);
406 if (parentList.isEmpty())
407 throw new IllegalArgumentException("'parents' is empty");
408
409 Resolver resolver = new Resolver(before, parentList, after, null);
410 resolver.resolveRequires(roots);
411
412 return new Configuration(parentList, resolver, true);
413 }
414
415 /**
416 * Resolves a collection of root modules, with service binding, to create
417 * configuration.
418 *
419 * <p> This method works exactly as specified by {@link
420 * #resolveRequires(ModuleFinder,List,ModuleFinder,Collection)
421 * resolveRequires} except that the graph of resolved modules is augmented
422 * with modules induced by the service-use dependence relation. </p>
423 *
424 * <p> More specifically, the root modules are resolved as if by calling
425 * {@code resolveRequires}. The resolved modules, and all modules in the
426 * parent configurations, with {@link ModuleDescriptor#uses() service
427 * dependences} are then examined. All modules found by the given module
428 * finders that {@link ModuleDescriptor#provides() provide} an
429 * implementation of one or more of the service types are added to the
430 * module graph and then resolved as if by calling the {@code
431 * resolveRequires} method. Adding modules to the module graph may
432 * introduce new service-use dependences and so the process works
433 * iteratively until no more modules are added. </p>
434 *
435 * <p> As service binding involves resolution then it may fail with {@link
436 * ResolutionException} for exactly the same reasons specified in
437 * {@code resolveRequires}. </p>
438 *
439 * @param before
440 * The <em>before</em> module finder to find modules
441 * @param parents
442 * The list parent configurations in search order
443 * @param after
444 * The <em>after</em> module finder to locate modules when not
445 * located by the {@code before} module finder or in parent
446 * configurations
447 * @param roots
448 * The possibly-empty collection of module names of the modules
449 * to resolve
450 *
451 * @return The configuration that is the result of resolving the given
452 * root modules
453 *
454 * @throws ResolutionException
455 * If resolution or the post-resolution checks fail
456 * @throws IllegalArgumentException
457 * If the list of parents is empty
458 * @throws SecurityException
459 * If locating a module is denied by the security manager
460 */
461 public static Configuration resolveRequiresAndUses(ModuleFinder before,
462 List<Configuration> parents,
463 ModuleFinder after,
464 Collection<String> roots)
465 {
466 Objects.requireNonNull(before);
467 Objects.requireNonNull(after);
468 Objects.requireNonNull(roots);
469
470 List<Configuration> parentList = new ArrayList<>(parents);
471 if (parentList.isEmpty())
472 throw new IllegalArgumentException("'parents' is empty");
473
474 Resolver resolver = new Resolver(before, parentList, after, null);
475 resolver.resolveRequires(roots).resolveUses();
476
477 return new Configuration(parentList, resolver, true);
478 }
479
480
481 /**
482 * Returns the <em>empty</em> configuration. There are no modules in the
483 * empty configuration. It has no parents.
484 *
485 * @return The empty configuration
486 */
487 public static Configuration empty() {
488 return EMPTY_CONFIGURATION;
489 }
490
491
492 /**
493 * Returns an unmodifiable list of this configuration's parents, in search
494 * order. If this is the {@linkplain #empty empty configuration} then an
495 * empty list is returned.
496 *
497 * @return A possibly-empty unmodifiable list of this parent configurations
498 */
499 public List<Configuration> parents() {
500 return parents;
501 }
502
503
504 /**
505 * Returns an immutable set of the resolved modules in this configuration.
506 *
507 * @return A possibly-empty unmodifiable set of the resolved modules
508 * in this configuration
509 */
510 public Set<ResolvedModule> modules() {
511 return modules;
512 }
513
514
515 /**
516 * Finds a resolved module in this configuration, or if not in this
517 * configuration, the {@linkplain #parents parent} configurations.
518 * Finding a module in parent configurations is equivalent to invoking
519 * {@code findModule} on each parent, in search order, until the module
520 * is found or all parents have been searched. In a <em>tree of
521 * configurations</em> then this is equivalent to a depth-first search.
522 *
523 * @param name
524 * The module name of the resolved module to find
525 *
526 * @return The resolved module with the given name or an empty {@code
527 * Optional} if there isn't a module with this name in this
528 * configuration or any parent configurations
529 */
530 public Optional<ResolvedModule> findModule(String name) {
531 Objects.requireNonNull(name);
532 ResolvedModule m = nameToModule.get(name);
533 if (m != null)
534 return Optional.of(m);
535
536 if (!parents.isEmpty()) {
537 return configurations()
538 .skip(1) // skip this configuration
539 .map(cf -> cf.nameToModule)
540 .filter(map -> map.containsKey(name))
541 .map(map -> map.get(name))
542 .findFirst();
543 }
544
545 return Optional.empty();
546 }
547
548
549 Set<ModuleDescriptor> descriptors() {
550 if (modules.isEmpty()) {
551 return Collections.emptySet();
552 } else {
553 return modules.stream()
554 .map(ResolvedModule::reference)
555 .map(ModuleReference::descriptor)
556 .collect(Collectors.toSet());
557 }
558 }
559
560 Set<ResolvedModule> reads(ResolvedModule m) {
561 return Collections.unmodifiableSet(graph.get(m));
562 }
563
564 /**
565 * Returns an ordered stream of configurations. The first element is this
566 * configuration, the remaining elements are the parent configurations
567 * in DFS order.
568 *
569 * @implNote For now, the assumption is that the number of elements will
570 * be very low and so this method does not use a specialized spliterator.
571 */
572 Stream<Configuration> configurations() {
573 List<Configuration> allConfigurations = this.allConfigurations;
574 if (allConfigurations == null) {
575 allConfigurations = new ArrayList<>();
576 Set<Configuration> visited = new HashSet<>();
577 Deque<Configuration> stack = new ArrayDeque<>();
578 visited.add(this);
579 stack.push(this);
580 while (!stack.isEmpty()) {
581 Configuration layer = stack.pop();
582 allConfigurations.add(layer);
583
584 // push in reverse order
585 for (int i = layer.parents.size() - 1; i >= 0; i--) {
586 Configuration parent = layer.parents.get(i);
587 if (!visited.contains(parent)) {
588 visited.add(parent);
589 stack.push(parent);
590 }
591 }
592 }
593 this.allConfigurations = Collections.unmodifiableList(allConfigurations);
594 }
595 return allConfigurations.stream();
596 }
597
598 private volatile List<Configuration> allConfigurations;
599
600
601 /**
602 * Returns a string describing this configuration.
603 *
604 * @return A possibly empty string describing this configuration
605 */
606 @Override
607 public String toString() {
608 return modules().stream()
609 .map(ResolvedModule::name)
610 .collect(Collectors.joining(", "));
611 }
612 }