1 /*
   2  * Copyright (c) 2005, 2019, 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 javax.lang.model.util;
  27 
  28 import java.util.ArrayList;
  29 import java.util.Collections;
  30 import java.util.List;
  31 import java.util.Map;
  32 import java.util.Set;
  33 import java.util.LinkedHashSet;
  34 
  35 import javax.lang.model.AnnotatedConstruct;
  36 import javax.lang.model.element.*;
  37 
  38 
  39 /**
  40  * Utility methods for operating on program elements.
  41  *
  42  * <p><b>Compatibility Note:</b> Methods may be added to this interface
  43  * in future releases of the platform.
  44  *
  45  * @author Joseph D. Darcy
  46  * @author Scott Seligman
  47  * @author Peter von der Ah&eacute;
  48  * @see javax.annotation.processing.ProcessingEnvironment#getElementUtils
  49  * @since 1.6
  50  */
  51 public interface Elements {
  52 
  53     /**
  54      * Returns a package given its fully qualified name if the package is unique in the environment.
  55      * If running with modules, all modules in the modules graph are searched for matching packages.
  56      *
  57      * @param name  fully qualified package name, or an empty string for an unnamed package
  58      * @return the specified package, or {@code null} if it cannot be uniquely found
  59      */
  60     PackageElement getPackageElement(CharSequence name);
  61 
  62     /**
  63      * Returns a package given its fully qualified name, as seen from the given module.
  64      *
  65      * @implSpec The default implementation of this method returns
  66      * {@code null}.
  67      *
  68      * @param name  fully qualified package name, or an empty string for an unnamed package
  69      * @param module module relative to which the lookup should happen
  70      * @return the specified package, or {@code null} if it cannot be found
  71      * @see #getAllPackageElements
  72      * @since 9
  73      */
  74     default PackageElement getPackageElement(ModuleElement module, CharSequence name) {
  75         return null;
  76     }
  77 
  78     /**
  79      * Returns all package elements with the given canonical name.
  80      *
  81      * There may be more than one package element with the same canonical
  82      * name if the package elements are in different modules.
  83      *
  84      * @implSpec The default implementation of this method calls
  85      * {@link #getAllModuleElements() getAllModuleElements} and stores
  86      * the result. If the set of modules is empty, {@link
  87      * #getPackageElement(CharSequence) getPackageElement(name)} is
  88      * called passing through the name argument. If {@code
  89      * getPackageElement(name)} is {@code null}, an empty set of
  90      * package elements is returned; otherwise, a single-element set
  91      * with the found package element is returned. If the set of
  92      * modules is nonempty, the modules are iterated over and any
  93      * non-{@code null} results of {@link
  94      * #getPackageElement(ModuleElement, CharSequence)
  95      * getPackageElement(module, name)} are accumulated into a
  96      * set. The set is then returned.
  97      *
  98      * @param name  the canonical name
  99      * @return the package elements, or an empty set if no package with the name can be found
 100      * @see #getPackageElement(ModuleElement, CharSequence)
 101      * @since 9
 102      */
 103     default Set<? extends PackageElement> getAllPackageElements(CharSequence name) {
 104         Set<? extends ModuleElement> modules = getAllModuleElements();
 105         if (modules.isEmpty()) {
 106             PackageElement packageElt = getPackageElement(name);
 107             return (packageElt != null) ?
 108                 Collections.singleton(packageElt):
 109                 Collections.emptySet();
 110         } else {
 111             Set<PackageElement> result = new LinkedHashSet<>(1); // Usually expect at most 1 result
 112             for (ModuleElement module: modules) {
 113                 PackageElement packageElt = getPackageElement(module, name);
 114                 if (packageElt != null)
 115                     result.add(packageElt);
 116             }
 117             return Collections.unmodifiableSet(result);
 118         }
 119     }
 120 
 121     /**
 122      * Returns a type element given its canonical name if the type element is unique in the environment.
 123      * If running with modules, all modules in the modules graph are searched for matching
 124      * type elements.
 125      *
 126      * @param name  the canonical name
 127      * @return the named type element, or {@code null} if it cannot be uniquely found
 128      */
 129     TypeElement getTypeElement(CharSequence name);
 130 
 131     /**
 132      * Returns a type element given its canonical name, as seen from the given module.
 133      *
 134      * @implSpec The default implementation of this method returns
 135      * {@code null}.
 136      *
 137      * @param name  the canonical name
 138      * @param module module relative to which the lookup should happen
 139      * @return the named type element, or {@code null} if it cannot be found
 140      * @see #getAllTypeElements
 141      * @since 9
 142      */
 143     default TypeElement getTypeElement(ModuleElement module, CharSequence name) {
 144         return null;
 145     }
 146 
 147     /**
 148      * Returns all type elements with the given canonical name.
 149      *
 150      * There may be more than one type element with the same canonical
 151      * name if the type elements are in different modules.
 152      *
 153      * @implSpec The default implementation of this method calls
 154      * {@link #getAllModuleElements() getAllModuleElements} and stores
 155      * the result. If the set of modules is empty, {@link
 156      * #getTypeElement(CharSequence) getTypeElement(name)} is called
 157      * passing through the name argument. If {@code
 158      * getTypeElement(name)} is {@code null}, an empty set of type
 159      * elements is returned; otherwise, a single-element set with the
 160      * found type element is returned. If the set of modules is
 161      * nonempty, the modules are iterated over and any non-{@code null}
 162      * results of {@link #getTypeElement(ModuleElement,
 163      * CharSequence) getTypeElement(module, name)} are accumulated
 164      * into a set. The set is then returned.
 165      *
 166      * @param name  the canonical name
 167      * @return the type elements, or an empty set if no type with the name can be found
 168      * @see #getTypeElement(ModuleElement, CharSequence)
 169      * @since 9
 170      */
 171     default Set<? extends TypeElement> getAllTypeElements(CharSequence name) {
 172         Set<? extends ModuleElement> modules = getAllModuleElements();
 173         if (modules.isEmpty()) {
 174             TypeElement typeElt = getTypeElement(name);
 175             return (typeElt != null) ?
 176                 Collections.singleton(typeElt):
 177                 Collections.emptySet();
 178         } else {
 179             Set<TypeElement> result = new LinkedHashSet<>(1); // Usually expect at most 1 result
 180             for (ModuleElement module: modules) {
 181                 TypeElement typeElt = getTypeElement(module, name);
 182                 if (typeElt != null)
 183                     result.add(typeElt);
 184             }
 185             return Collections.unmodifiableSet(result);
 186         }
 187     }
 188 
 189     /**
 190      * Returns a module element given its fully qualified name.
 191      *
 192      * If the requested module cannot be found, {@code null} is
 193      * returned. One situation where a module cannot be found is if
 194      * the environment does not include modules, such as an annotation
 195      * processing environment configured for a {@linkplain
 196      * javax.annotation.processing.ProcessingEnvironment#getSourceVersion
 197      * source version} without modules.
 198      *
 199      * @implSpec The default implementation of this method returns
 200      * {@code null}.
 201      *
 202      * @param name  the name, or an empty string for an unnamed module
 203      * @return the named module element, or {@code null} if it cannot be found
 204      * @see #getAllModuleElements
 205      * @since 9
 206      * @spec JPMS
 207      */
 208     default ModuleElement getModuleElement(CharSequence name) {
 209         return null;
 210     }
 211 
 212     /**
 213      * Returns all module elements in the current environment.
 214      *
 215      * If no modules are present, an empty set is returned. One
 216      * situation where no modules are present occurs when the
 217      * environment does not include modules, such as an annotation
 218      * processing environment configured for a {@linkplain
 219      * javax.annotation.processing.ProcessingEnvironment#getSourceVersion
 220      * source version} without modules.
 221      *
 222      * @implSpec The default implementation of this method returns
 223      * an empty set.
 224      *
 225      * @return the known module elements, or an empty set if there are no modules
 226      * @see #getModuleElement(CharSequence)
 227      * @since 9
 228      */
 229     default Set<? extends ModuleElement> getAllModuleElements() {
 230         return Collections.emptySet();
 231     }
 232 
 233     /**
 234      * Returns the values of an annotation's elements, including defaults.
 235      *
 236      * @see AnnotationMirror#getElementValues()
 237      * @param a  annotation to examine
 238      * @return the values of the annotation's elements, including defaults
 239      */
 240     Map<? extends ExecutableElement, ? extends AnnotationValue>
 241             getElementValuesWithDefaults(AnnotationMirror a);
 242 
 243     /**
 244      * Returns the text of the documentation (&quot;Javadoc&quot;)
 245      * comment of an element.
 246      *
 247      * <p> A documentation comment of an element is a comment that
 248      * begins with "{@code /**}" , ends with a separate
 249      * "<code>*/</code>", and immediately precedes the element,
 250      * ignoring white space.  Therefore, a documentation comment
 251      * contains at least three"{@code *}" characters.  The text
 252      * returned for the documentation comment is a processed form of
 253      * the comment as it appears in source code.  The leading "{@code
 254      * /**}" and trailing "<code>*/</code>" are removed.  For lines
 255      * of the comment starting after the initial "{@code /**}",
 256      * leading white space characters are discarded as are any
 257      * consecutive "{@code *}" characters appearing after the white
 258      * space or starting the line.  The processed lines are then
 259      * concatenated together (including line terminators) and
 260      * returned.
 261      *
 262      * @param e  the element being examined
 263      * @return the documentation comment of the element, or {@code null}
 264      *          if there is none
 265      * @jls 3.6 White Space
 266      */
 267     String getDocComment(Element e);
 268 
 269     /**
 270      * Returns {@code true} if the element is deprecated, {@code false} otherwise.
 271      *
 272      * @param e  the element being examined
 273      * @return {@code true} if the element is deprecated, {@code false} otherwise
 274      */
 275     boolean isDeprecated(Element e);
 276 
 277     /**
 278      * Returns the <em>origin</em> of the given element.
 279      *
 280      * <p>Note that if this method returns {@link Origin#EXPLICIT
 281      * EXPLICIT} and the element was created from a class file, then
 282      * the element may not, in fact, correspond to an explicitly
 283      * declared construct in source code. This is due to limitations
 284      * of the fidelity of the class file format in preserving
 285      * information from source code. For example, at least some
 286      * versions of the class file format do not preserve whether a
 287      * constructor was explicitly declared by the programmer or was
 288      * implicitly declared as the <em>default constructor</em>.
 289      *
 290      * @implSpec The default implementation of this method returns
 291      * {@link Origin#EXPLICIT EXPLICIT}.
 292      *
 293      * @param e  the element being examined
 294      * @return the origin of the given element
 295      * @since 9
 296      */
 297     default Origin getOrigin(Element e) {
 298         return Origin.EXPLICIT;
 299     }
 300 
 301     /**
 302      * Returns the <em>origin</em> of the given annotation mirror.
 303      *
 304      * An annotation mirror is {@linkplain Origin#MANDATED mandated}
 305      * if it is an implicitly declared <em>container annotation</em>
 306      * used to hold repeated annotations of a repeatable annotation
 307      * type.
 308      *
 309      * <p>Note that if this method returns {@link Origin#EXPLICIT
 310      * EXPLICIT} and the annotation mirror was created from a class
 311      * file, then the element may not, in fact, correspond to an
 312      * explicitly declared construct in source code. This is due to
 313      * limitations of the fidelity of the class file format in
 314      * preserving information from source code. For example, at least
 315      * some versions of the class file format do not preserve whether
 316      * an annotation was explicitly declared by the programmer or was
 317      * implicitly declared as a <em>container annotation</em>.
 318      *
 319      * @implSpec The default implementation of this method returns
 320      * {@link Origin#EXPLICIT EXPLICIT}.
 321      *
 322      * @param c the construct the annotation mirror modifies
 323      * @param a the annotation mirror being examined
 324      * @return the origin of the given annotation mirror
 325      * @jls 9.6.3 Repeatable Annotation Types
 326      * @jls 9.7.5 Multiple Annotations of the Same Type
 327      * @since 9
 328      */
 329     default Origin getOrigin(AnnotatedConstruct c,
 330                              AnnotationMirror a) {
 331         return Origin.EXPLICIT;
 332     }
 333 
 334     /**
 335      * Returns the <em>origin</em> of the given module directive.
 336      *
 337      * <p>Note that if this method returns {@link Origin#EXPLICIT
 338      * EXPLICIT} and the module directive was created from a class
 339      * file, then the module directive may not, in fact, correspond to
 340      * an explicitly declared construct in source code. This is due to
 341      * limitations of the fidelity of the class file format in
 342      * preserving information from source code. For example, at least
 343      * some versions of the class file format do not preserve whether
 344      * a {@code uses} directive was explicitly declared by the
 345      * programmer or was added as a synthetic construct.
 346      *
 347      * <p>Note that an implementation may not be able to reliably
 348      * determine the origin status of the directive if the directive
 349      * is created from a class file due to limitations of the fidelity
 350      * of the class file format in preserving information from source
 351      * code.
 352      *
 353      * @implSpec The default implementation of this method returns
 354      * {@link Origin#EXPLICIT EXPLICIT}.
 355      *
 356      * @param m the module of the directive
 357      * @param directive  the module directive being examined
 358      * @return the origin of the given directive
 359      * @since 9
 360      */
 361     default Origin getOrigin(ModuleElement m,
 362                              ModuleElement.Directive directive) {
 363         return Origin.EXPLICIT;
 364     }
 365 
 366     /**
 367      * The <em>origin</em> of an element or other language model
 368      * item. The origin of an element or item models how a construct
 369      * in a program is declared in the source code, explicitly,
 370      * implicitly, etc.
 371      *
 372      * <p>Note that it is possible additional kinds of origin values
 373      * will be added in future versions of the platform.
 374      *
 375      * @jls 13.1 The Form of a Binary
 376      * @since 9
 377      */
 378     public enum Origin {
 379         /**
 380          * Describes a construct explicitly declared in source code.
 381          */
 382         EXPLICIT,
 383 
 384        /**
 385          * A mandated construct is one that is not explicitly declared
 386          * in the source code, but whose presence is mandated by the
 387          * specification. Such a construct is said to be implicitly
 388          * declared.
 389          *
 390          * One example of a mandated element is a <em>default
 391          * constructor</em> in a class that contains no explicit
 392          * constructor declarations.
 393          *
 394          * Another example of a mandated construct is an implicitly
 395          * declared <em>container annotation</em> used to hold
 396          * multiple annotations of a repeatable annotation type.
 397          *
 398          * @jls 8.8.9 Default Constructor
 399          * @jls 8.9.3 Enum Members
 400          * @jls 9.6.3 Repeatable Annotation Types
 401          * @jls 9.7.5 Multiple Annotations of the Same Type
 402          */
 403         MANDATED,
 404 
 405        /**
 406          * A synthetic construct is one that is neither implicitly nor
 407          * explicitly declared in the source code. Such a construct is
 408          * typically a translation artifact created by a compiler.
 409          */
 410         SYNTHETIC;
 411 
 412         /**
 413          * Returns {@code true} for values corresponding to constructs
 414          * that are implicitly or explicitly declared, {@code false}
 415          * otherwise.
 416          * @return {@code true} for {@link EXPLICIT} and {@link
 417          * MANDATED}, {@code false} otherwise.
 418          */
 419         public boolean isDeclared() {
 420             return this != SYNTHETIC;
 421         }
 422     }
 423 
 424     /**
 425      * Returns {@code true} if the executable element is a bridge
 426      * method, {@code false} otherwise.
 427      *
 428      * @implSpec The default implementation of this method returns {@code false}.
 429      *
 430      * @param e  the executable being examined
 431      * @return {@code true} if the executable element is a bridge
 432      * method, {@code false} otherwise
 433      * @since 9
 434      */
 435     default boolean isBridge(ExecutableElement e) {
 436         return false;
 437     }
 438 
 439     /**
 440      * Returns the <i>binary name</i> of a type element.
 441      *
 442      * @param type  the type element being examined
 443      * @return the binary name
 444      *
 445      * @see TypeElement#getQualifiedName
 446      * @jls 13.1 The Form of a Binary
 447      */
 448     Name getBinaryName(TypeElement type);
 449 
 450 
 451     /**
 452      * Returns the package of an element.  The package of a package is
 453      * itself.
 454      * The package of a module is {@code null}.
 455      *
 456      * @param type the element being examined
 457      * @return the package of an element
 458      */
 459     PackageElement getPackageOf(Element type);
 460 
 461     /**
 462      * Returns the module of an element.  The module of a module is
 463      * itself.
 464      * If there is no module for the element, null is returned. One situation where there is
 465      * no module for an element is if the environment does not include modules, such as
 466      * an annotation processing environment configured for
 467      * a {@linkplain
 468      * javax.annotation.processing.ProcessingEnvironment#getSourceVersion
 469      * source version} without modules.
 470      *
 471      * @implSpec The default implementation of this method returns
 472      * {@code null}.
 473      *
 474      * @param type the element being examined
 475      * @return the module of an element
 476      * @since 9
 477      * @spec JPMS
 478      */
 479     default ModuleElement getModuleOf(Element type) {
 480         return null;
 481     }
 482 
 483     /**
 484      * Returns all members of a type element, whether inherited or
 485      * declared directly.  For a class the result also includes its
 486      * constructors, but not local or anonymous classes.
 487      *
 488      * @apiNote Elements of certain kinds can be isolated using
 489      * methods in {@link ElementFilter}.
 490      *
 491      * @param type  the type being examined
 492      * @return all members of the type
 493      * @see Element#getEnclosedElements
 494      */
 495     List<? extends Element> getAllMembers(TypeElement type);
 496 
 497     /**
 498      * Returns all annotations <i>present</i> on an element, whether
 499      * directly present or present via inheritance.
 500      *
 501      * @param e  the element being examined
 502      * @return all annotations of the element
 503      * @see Element#getAnnotationMirrors
 504      * @see javax.lang.model.AnnotatedConstruct
 505      */
 506     List<? extends AnnotationMirror> getAllAnnotationMirrors(Element e);
 507 
 508     /**
 509      * Tests whether one type, method, or field hides another.
 510      *
 511      * @param hider   the first element
 512      * @param hidden  the second element
 513      * @return {@code true} if and only if the first element hides
 514      *          the second
 515      * @jls 8.4.8 Inheritance, Overriding, and Hiding
 516      */
 517     boolean hides(Element hider, Element hidden);
 518 
 519     /**
 520      * Tests whether one method, as a member of a given type,
 521      * overrides another method.
 522      * When a non-abstract method overrides an abstract one, the
 523      * former is also said to <i>implement</i> the latter.
 524      *
 525      * <p> In the simplest and most typical usage, the value of the
 526      * {@code type} parameter will simply be the class or interface
 527      * directly enclosing {@code overrider} (the possibly-overriding
 528      * method).  For example, suppose {@code m1} represents the method
 529      * {@code String.hashCode} and {@code m2} represents {@code
 530      * Object.hashCode}.  We can then ask whether {@code m1} overrides
 531      * {@code m2} within the class {@code String} (it does):
 532      *
 533      * <blockquote>
 534      * {@code assert elements.overrides(m1, m2,
 535      *          elements.getTypeElement("java.lang.String")); }
 536      * </blockquote>
 537      *
 538      * A more interesting case can be illustrated by the following example
 539      * in which a method in type {@code A} does not override a
 540      * like-named method in type {@code B}:
 541      *
 542      * <blockquote>
 543      * {@code class A { public void m() {} } }<br>
 544      * {@code interface B { void m(); } }<br>
 545      * ...<br>
 546      * {@code m1 = ...;  // A.m }<br>
 547      * {@code m2 = ...;  // B.m }<br>
 548      * {@code assert ! elements.overrides(m1, m2,
 549      *          elements.getTypeElement("A")); }
 550      * </blockquote>
 551      *
 552      * When viewed as a member of a third type {@code C}, however,
 553      * the method in {@code A} does override the one in {@code B}:
 554      *
 555      * <blockquote>
 556      * {@code class C extends A implements B {} }<br>
 557      * ...<br>
 558      * {@code assert elements.overrides(m1, m2,
 559      *          elements.getTypeElement("C")); }
 560      * </blockquote>
 561      *
 562      * @param overrider  the first method, possible overrider
 563      * @param overridden  the second method, possibly being overridden
 564      * @param type   the type of which the first method is a member
 565      * @return {@code true} if and only if the first method overrides
 566      *          the second
 567      * @jls 8.4.8 Inheritance, Overriding, and Hiding
 568      * @jls 9.4.1 Inheritance and Overriding
 569      */
 570     boolean overrides(ExecutableElement overrider, ExecutableElement overridden,
 571                       TypeElement type);
 572 
 573     /**
 574      * Returns the text of a <i>constant expression</i> representing a
 575      * primitive value or a string.
 576      * The text returned is in a form suitable for representing the value
 577      * in source code.
 578      *
 579      * @param value  a primitive value or string
 580      * @return the text of a constant expression
 581      * @throws IllegalArgumentException if the argument is not a primitive
 582      *          value or string
 583      *
 584      * @see VariableElement#getConstantValue()
 585      */
 586     String getConstantExpression(Object value);
 587 
 588     /**
 589      * Prints a representation of the elements to the given writer in
 590      * the specified order.  The main purpose of this method is for
 591      * diagnostics.  The exact format of the output is <em>not</em>
 592      * specified and is subject to change.
 593      *
 594      * @param w the writer to print the output to
 595      * @param elements the elements to print
 596      */
 597     void printElements(java.io.Writer w, Element... elements);
 598 
 599     /**
 600      * Return a name with the same sequence of characters as the
 601      * argument.
 602      *
 603      * @param cs the character sequence to return as a name
 604      * @return a name with the same sequence of characters as the argument
 605      */
 606     Name getName(CharSequence cs);
 607 
 608     /**
 609      * Returns {@code true} if the type element is a functional interface, {@code false} otherwise.
 610      *
 611      * @param type the type element being examined
 612      * @return {@code true} if the element is a functional interface, {@code false} otherwise
 613      * @jls 9.8 Functional Interfaces
 614      * @since 1.8
 615      */
 616     boolean isFunctionalInterface(TypeElement type);
 617 
 618     /**
 619      * Returns the executable element for the getter associated with the given variable element.
 620      *
 621      * @implSpec The default implementation of this method returns
 622      * {@code null}.
 623      *
 624      * @param variableElement the field for which the getter is to be found.
 625      * @return the field's getter; otherwise {@code null} if there is no getter.
 626      * @since amber
 627      */
 628     default ExecutableElement getterFor(VariableElement variableElement) {
 629         return null;
 630     }
 631 
 632     /**
 633      * Returns the executable element for the setter associated with the given variable element.
 634      *
 635      * @implSpec The default implementation of this method returns
 636      * {@code null}.
 637      *
 638      * @param variableElement the field for which the setter is to be found.
 639      * @return the field's setter; otherwise {@code null} if there is no getter.
 640      * @since amber
 641      */
 642     default ExecutableElement setterFor(VariableElement variableElement) {
 643         return null;
 644     }
 645 
 646     /**
 647      * Return {@code true} if the type element is sealed, {@code
 648      * false} otherwise. This method takes into account non-sealing of
 649      * types.
 650      *
 651      * @implSpec The default implementation of this method returns
 652      * {@code false}.
 653      *
 654      * @param type the type element being examined
 655      * @return {@code true} if the type element is sealed, {@code false} otherwise
 656      * @since amber
 657      */
 658     default boolean isSealed(TypeElement type) {
 659         return false;
 660     }
 661 }