      1 /*
      2  * Copyright (c) 2000, 2020, 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;
     27
     28 import jdk.internal.loader.BuiltinClassLoader;
     29 import jdk.internal.misc.VM;
     30 import jdk.internal.module.ModuleHashes;
     31 import jdk.internal.module.ModuleReferenceImpl;
     32
     33 import java.lang.module.ModuleDescriptor.Version;
     34 import java.lang.module.ModuleReference;
     35 import java.lang.module.ResolvedModule;
     36 import java.util.HashSet;
     37 import java.util.Objects;
     38 import java.util.Optional;
     39 import java.util.Set;
     40
     41 /**
     42  * An element in a stack trace, as returned by {@link
     43  * Throwable#getStackTrace()}.  Each element represents a single stack frame.
     44  * All stack frames except for the one at the top of the stack represent
     45  * a method invocation.  The frame at the top of the stack represents the
     46  * execution point at which the stack trace was generated.  Typically,
     47  * this is the point at which the throwable corresponding to the stack trace
     48  * was created.
     49  *
     50  * @since  1.4
     51  * @author Josh Bloch
     52  */
     53 public final class StackTraceElement implements java.io.Serializable {
     54
     55     // For Throwables and StackWalker, the VM initially sets this field to a
     56     // reference to the declaring Class.  The Class reference is used to
     57     // construct the 'format' bitmap, and then is cleared.
     58     //
     59     // For STEs constructed using the public constructors, this field is not used.
     60     private transient Class<?> declaringClassObject;
     61
     62     // Normally initialized by VM

     63     private String classLoaderName;

     64     private String moduleName;

     65     private String moduleVersion;

     66     private String declaringClass;

     67     private String methodName;

     68     private String fileName;

     69     private int    lineNumber;

     70     private byte   format = 0; // Default to show all
     71
     72     /**
     73      * Creates a stack trace element representing the specified execution
     74      * point. The {@link #getModuleName module name} and {@link
     75      * #getModuleVersion module version} of the stack trace element will
     76      * be {@code null}.
     77      *
     78      * @param declaringClass the fully qualified name of the class containing
     79      *        the execution point represented by the stack trace element
     80      * @param methodName the name of the method containing the execution point
     81      *        represented by the stack trace element
     82      * @param fileName the name of the file containing the execution point
     83      *         represented by the stack trace element, or {@code null} if
     84      *         this information is unavailable
     85      * @param lineNumber the line number of the source line containing the
     86      *         execution point represented by this stack trace element, or
     87      *         a negative number if this information is unavailable. A value
     88      *         of -2 indicates that the method containing the execution point
     89      *         is a native method
     90      * @throws NullPointerException if {@code declaringClass} or
     91      *         {@code methodName} is null
     92      * @since 1.5
     93      * @revised 9
     94      * @spec JPMS
     95      */
     96     public StackTraceElement(String declaringClass, String methodName,
     97                              String fileName, int lineNumber) {
     98         this(null, null, null, declaringClass, methodName, fileName, lineNumber);
     99     }
    100
    101     /**
    102      * Creates a stack trace element representing the specified execution
    103      * point.
    104      *
    105      * @param classLoaderName the class loader name if the class loader of
    106      *        the class containing the execution point represented by
    107      *        the stack trace is named; otherwise {@code null}
    108      * @param moduleName the module name if the class containing the
    109      *        execution point represented by the stack trace is in a named
    110      *        module; otherwise {@code null}
    111      * @param moduleVersion the module version if the class containing the
    112      *        execution point represented by the stack trace is in a named
    113      *        module that has a version; otherwise {@code null}
    114      * @param declaringClass the fully qualified name of the class containing
    115      *        the execution point represented by the stack trace element
    116      * @param methodName the name of the method containing the execution point
    117      *        represented by the stack trace element
    118      * @param fileName the name of the file containing the execution point
    119      *        represented by the stack trace element, or {@code null} if
    120      *        this information is unavailable
    121      * @param lineNumber the line number of the source line containing the
    122      *        execution point represented by this stack trace element, or
    123      *        a negative number if this information is unavailable. A value
    124      *        of -2 indicates that the method containing the execution point
    125      *        is a native method
    126      *
    127      * @throws NullPointerException if {@code declaringClass} is {@code null}
    128      *         or {@code methodName} is {@code null}
    129      *
    130      * @since 9
    131      * @spec JPMS
    132      */
    133     public StackTraceElement(String classLoaderName,
    134                              String moduleName, String moduleVersion,
    135                              String declaringClass, String methodName,
    136                              String fileName, int lineNumber) {
    137         this.classLoaderName = classLoaderName;
    138         this.moduleName      = moduleName;
    139         this.moduleVersion   = moduleVersion;
    140         this.declaringClass  = Objects.requireNonNull(declaringClass, "Declaring class is null");
    141         this.methodName      = Objects.requireNonNull(methodName, "Method name is null");
    142         this.fileName        = fileName;
    143         this.lineNumber      = lineNumber;
    144     }
    145
    146     /*
    147      * Private constructor for the factory methods to create StackTraceElement
    148      * for Throwable and StackFrameInfo
    149      */
    150     private StackTraceElement() {}
    151
    152     /**
    153      * Returns the name of the source file containing the execution point
    154      * represented by this stack trace element.  Generally, this corresponds
    155      * to the {@code SourceFile} attribute of the relevant {@code class}
    156      * file (as per <cite>The Java Virtual Machine Specification</cite>, Section
    157      * {@jvms 4.7.7}).  In some systems, the name may refer to some source code unit
    158      * other than a file, such as an entry in source repository.
    159      *
    160      * @return the name of the file containing the execution point
    161      *         represented by this stack trace element, or {@code null} if
    162      *         this information is unavailable.
    163      */
    164     public String getFileName() {
    165         return fileName;
    166     }
    167
    168     /**
    169      * Returns the line number of the source line containing the execution
    170      * point represented by this stack trace element.  Generally, this is
    171      * derived from the {@code LineNumberTable} attribute of the relevant
    172      * {@code class} file (as per <cite>The Java Virtual Machine
    173      * Specification</cite>, Section {@jvms 4.7.8}).
    174      *
    175      * @return the line number of the source line containing the execution
    176      *         point represented by this stack trace element, or a negative
    177      *         number if this information is unavailable.
    178      */
    179     public int getLineNumber() {
    180         return lineNumber;
    181     }
    182
    183     /**
    184      * Returns the module name of the module containing the execution point
    185      * represented by this stack trace element.
    186      *
    187      * @return the module name of the {@code Module} containing the execution
    188      *         point represented by this stack trace element; {@code null}
    189      *         if the module name is not available.
    190      * @since 9
    191      * @spec JPMS
    192      * @see Module#getName()
    193      */
    194     public String getModuleName() {
    195         return moduleName;
    196     }
    197
    198     /**
    199      * Returns the module version of the module containing the execution point
    200      * represented by this stack trace element.
    201      *
    202      * @return the module version of the {@code Module} containing the execution
    203      *         point represented by this stack trace element; {@code null}
    204      *         if the module version is not available.
    205      * @since 9
    206      * @spec JPMS
    207      * @see java.lang.module.ModuleDescriptor.Version
    208      */
    209     public String getModuleVersion() {
    210         return moduleVersion;
    211     }
    212
    213     /**
    214      * Returns the name of the class loader of the class containing the
    215      * execution point represented by this stack trace element.
    216      *
    217      * @return the name of the class loader of the class containing the execution
    218      *         point represented by this stack trace element; {@code null}
    219      *         if the class loader is not named.
    220      *
    221      * @since 9
    222      * @spec JPMS
    223      * @see java.lang.ClassLoader#getName()
    224      */
    225     public String getClassLoaderName() {
    226         return classLoaderName;
    227     }
    228
    229     /**
    230      * Returns the fully qualified name of the class containing the
    231      * execution point represented by this stack trace element.
    232      *
    233      * @return the fully qualified name of the {@code Class} containing
    234      *         the execution point represented by this stack trace element.
    235      */
    236     public String getClassName() {
    237         return declaringClass;
    238     }
    239
    240     /**
    241      * Returns the name of the method containing the execution point
    242      * represented by this stack trace element.  If the execution point is
    243      * contained in an instance or class initializer, this method will return
    244      * the appropriate <i>special method name</i>, {@code <init>} or
    245      * {@code <clinit>}, as per Section {@jvms 3.9} of <cite>The Java Virtual
    246      * Machine Specification</cite>.
    247      *
    248      * @return the name of the method containing the execution point
    249      *         represented by this stack trace element.
    250      */
    251     public String getMethodName() {
    252         return methodName;
    253     }
    254
    255     /**
    256      * Returns true if the method containing the execution point
    257      * represented by this stack trace element is a native method.
    258      *
    259      * @return {@code true} if the method containing the execution point
    260      *         represented by this stack trace element is a native method.
    261      */
    262     public boolean isNativeMethod() {
    263         return lineNumber == -2;
    264     }
    265
    266     /**
    267      * Returns a string representation of this stack trace element.
    268      *
    269      * @apiNote The format of this string depends on the implementation, but the
    270      * following examples may be regarded as typical:
    271      * <ul>
    272      * <li>
    273      *     "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java:101)}"
    274      * - See the description below.
    275      * </li>
    276      * <li>
    277      *     "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java)}"
    278      * - The line number is unavailable.
    279      * </li>
    280      * <li>
    281      *     "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Unknown Source)}"
    282      * - Neither the file name nor the line number is available.
    283      * </li>
    284      * <li>
    285      *     "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Native Method)}"
    286      * - The method containing the execution point is a native method.
    287      * </li>
    288      * <li>
    289      *     "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}"
    290      * - The class of the execution point is defined in the unnamed module of
    291      * the class loader named {@code com.foo.loader}.
    292      * </li>
    293      * <li>
    294      *     "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}"
    295      * - The class of the execution point is defined in {@code acme} module
    296      * loaded by a built-in class loader such as the application class loader.
    297      * </li>
    298      * <li>
    299      *     "{@code MyClass.mash(MyClass.java:9)}"
    300      * - {@code MyClass} class is on the application class path.
    301      * </li>
    302      * </ul>
    303      *
    304      * <p> The first example shows a stack trace element consisting of
    305      * three elements, each separated by {@code "/"}, followed by
    306      * the source file name and the line number of the source line
    307      * containing the execution point.
    308      *
    309      * The first element "{@code com.foo.loader}" is
    310      * the name of the class loader.  The second element "{@code foo@9.0}"
    311      * is the module name and version.  The third element is the method
    312      * containing the execution point; "{@code com.foo.Main"}" is the
    313      * fully-qualified class name and "{@code run}" is the name of the method.
    314      * "{@code Main.java}" is the source file name and "{@code 101}" is
    315      * the line number.
    316      *
    317      * <p> If a class is defined in an <em>unnamed module</em>
    318      * then the second element is omitted as shown in
    319      * "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}".
    320      *
    321      * <p> If the class loader is a <a href="ClassLoader.html#builtinLoaders">
    322      * built-in class loader</a> or is not named then the first element
    323      * and its following {@code "/"} are omitted as shown in
    324      * "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}".
    325      * If the first element is omitted and the module is an unnamed module,
    326      * the second element and its following {@code "/"} are also omitted
    327      * as shown in "{@code MyClass.mash(MyClass.java:9)}".
    328      *
    329      * <p> The {@code toString} method may return two different values on two
    330      * {@code StackTraceElement} instances that are
    331      * {@linkplain #equals(Object) equal}, for example one created via the
    332      * constructor, and one obtained from {@link java.lang.Throwable} or
    333      * {@link java.lang.StackWalker.StackFrame}, where an implementation may
    334      * choose to omit some element in the returned string.
    335      *
    336      * @revised 9
    337      * @spec JPMS
    338      * @see    Throwable#printStackTrace()
    339      */
    340     public String toString() {
    341         String s = "";
    342         if (!dropClassLoaderName() && classLoaderName != null &&
    343                 !classLoaderName.isEmpty()) {
    344             s += classLoaderName + "/";
    345         }
    346         if (moduleName != null && !moduleName.isEmpty()) {
    347             s += moduleName;
    348
    349             if (!dropModuleVersion() && moduleVersion != null &&
    350                     !moduleVersion.isEmpty()) {
    351                 s += "@" + moduleVersion;
    352             }
    353         }
    354         s = s.isEmpty() ? declaringClass : s + "/" + declaringClass;
    355
    356         return s + "." + methodName + "(" +
    357              (isNativeMethod() ? "Native Method)" :
    358               (fileName != null && lineNumber >= 0 ?
    359                fileName + ":" + lineNumber + ")" :
    360                 (fileName != null ?  ""+fileName+")" : "Unknown Source)")));
    361     }
    362
    363     /**
    364      * Returns true if the specified object is another
    365      * {@code StackTraceElement} instance representing the same execution
    366      * point as this instance.  Two stack trace elements {@code a} and
    367      * {@code b} are equal if and only if:
    368      * <pre>{@code
    369      *     equals(a.getClassLoaderName(), b.getClassLoaderName()) &&
    370      *     equals(a.getModuleName(), b.getModuleName()) &&
    371      *     equals(a.getModuleVersion(), b.getModuleVersion()) &&
    372      *     equals(a.getClassName(), b.getClassName()) &&
    373      *     equals(a.getMethodName(), b.getMethodName())
    374      *     equals(a.getFileName(), b.getFileName()) &&
    375      *     a.getLineNumber() == b.getLineNumber()
    376      *
    377      * }</pre>
    378      * where {@code equals} has the semantics of {@link
    379      * java.util.Objects#equals(Object, Object) Objects.equals}.
    380      *
    381      * @param  obj the object to be compared with this stack trace element.
    382      * @return true if the specified object is another
    383      *         {@code StackTraceElement} instance representing the same
    384      *         execution point as this instance.
    385      *
    386      * @revised 9
    387      * @spec JPMS
    388      */
    389     public boolean equals(Object obj) {
    390         if (obj==this)
    391             return true;
    392         if (!(obj instanceof StackTraceElement))
    393             return false;
    394         StackTraceElement e = (StackTraceElement)obj;
    395         return Objects.equals(classLoaderName, e.classLoaderName) &&
    396             Objects.equals(moduleName, e.moduleName) &&
    397             Objects.equals(moduleVersion, e.moduleVersion) &&
    398             e.declaringClass.equals(declaringClass) &&
    399             e.lineNumber == lineNumber &&
    400             Objects.equals(methodName, e.methodName) &&
    401             Objects.equals(fileName, e.fileName);
    402     }
    403
    404     /**
    405      * Returns a hash code value for this stack trace element.
    406      */
    407     public int hashCode() {
    408         int result = 31*declaringClass.hashCode() + methodName.hashCode();
    409         result = 31*result + Objects.hashCode(classLoaderName);
    410         result = 31*result + Objects.hashCode(moduleName);
    411         result = 31*result + Objects.hashCode(moduleVersion);
    412         result = 31*result + Objects.hashCode(fileName);
    413         result = 31*result + lineNumber;
    414         return result;
    415     }
    416
    417
    418     /**
    419      * Called from of() methods to set the 'format' bitmap using the Class
    420      * reference stored in declaringClassObject, and then clear the reference.
    421      *
    422      * <p>
    423      * If the module is a non-upgradeable JDK module, then set
    424      * JDK_NON_UPGRADEABLE_MODULE to omit its version string.
    425      * <p>
    426      * If the loader is one of the built-in loaders (`boot`, `platform`, or `app`)
    427      * then set BUILTIN_CLASS_LOADER to omit the first element (`<loader>/`).
    428      */
    429     private synchronized void computeFormat() {
    430         try {
    431             Class<?> cls = (Class<?>) declaringClassObject;
    432             ClassLoader loader = cls.getClassLoader0();
    433             Module m = cls.getModule();
    434             byte bits = 0;
    435
    436             // First element - class loader name
    437             // Call package-private ClassLoader::name method
    438
    439             if (loader instanceof BuiltinClassLoader) {
    440                 bits |= BUILTIN_CLASS_LOADER;
    441             }
    442
    443             // Second element - module name and version
    444
    445             // Omit if is a JDK non-upgradeable module (recorded in the hashes
    446             // in java.base)
    447             if (isHashedInJavaBase(m)) {
    448                 bits |= JDK_NON_UPGRADEABLE_MODULE;
    449             }
    450             format = bits;
    451         } finally {
    452             // Class reference no longer needed, clear it
    453             declaringClassObject = null;
    454         }
    455     }
    456
    457     private static final byte BUILTIN_CLASS_LOADER       = 0x1;
    458     private static final byte JDK_NON_UPGRADEABLE_MODULE = 0x2;
    459
    460     private boolean dropClassLoaderName() {
    461         return (format & BUILTIN_CLASS_LOADER) == BUILTIN_CLASS_LOADER;
    462     }
    463
    464     private boolean dropModuleVersion() {
    465         return (format & JDK_NON_UPGRADEABLE_MODULE) == JDK_NON_UPGRADEABLE_MODULE;
    466     }
    467
    468     /**
    469      * Returns true if the module is hashed with java.base.
    470      * <p>
    471      * This method returns false when running on the exploded image
    472      * since JDK modules are not hashed. They have no Version attribute
    473      * and so "@<version>" part will be omitted anyway.
    474      */
    475     private static boolean isHashedInJavaBase(Module m) {
    476         // return true if module system is not initialized as the code
    477         // must be in java.base
    478         if (!VM.isModuleSystemInited())
    479             return true;
    480
    481         return ModuleLayer.boot() == m.getLayer() && HashedModules.contains(m);
    482     }
    483
    484     /*
    485      * Finds JDK non-upgradeable modules, i.e. the modules that are
    486      * included in the hashes in java.base.
    487      */
    488     private static class HashedModules {
    489         static Set<String> HASHED_MODULES = hashedModules();
    490
    491         static Set<String> hashedModules() {
    492
    493             Optional<ResolvedModule> resolvedModule = ModuleLayer.boot()
    494                     .configuration()
    495                     .findModule("java.base");
    496             assert resolvedModule.isPresent();
    497             ModuleReference mref = resolvedModule.get().reference();
    498             assert mref instanceof ModuleReferenceImpl;
    499             ModuleHashes hashes = ((ModuleReferenceImpl)mref).recordedHashes();
    500             if (hashes != null) {
    501                 Set<String> names = new HashSet<>(hashes.names());
    502                 names.add("java.base");
    503                 return names;
    504             }
    505
    506             return Set.of();
    507         }
    508
    509         static boolean contains(Module m) {
    510             return HASHED_MODULES.contains(m.getName());
    511         }
    512     }
    513
    514
    515     /*
    516      * Returns an array of StackTraceElements of the given depth
    517      * filled from the backtrace of a given Throwable.
    518      */
    519     static StackTraceElement[] of(Throwable x, int depth) {
    520         StackTraceElement[] stackTrace = new StackTraceElement[depth];
    521         for (int i = 0; i < depth; i++) {
    522             stackTrace[i] = new StackTraceElement();
    523         }
    524
    525         // VM to fill in StackTraceElement
    526         initStackTraceElements(stackTrace, x);
    527
    528         // ensure the proper StackTraceElement initialization
    529         for (StackTraceElement ste : stackTrace) {
    530             ste.computeFormat();
    531         }
    532         return stackTrace;
    533     }
    534
    535     /*
    536      * Returns a StackTraceElement from a given StackFrameInfo.
    537      */
    538     static StackTraceElement of(StackFrameInfo sfi) {
    539         StackTraceElement ste = new StackTraceElement();
    540         initStackTraceElement(ste, sfi);
    541
    542         ste.computeFormat();
    543         return ste;
    544     }
    545
    546     /*
    547      * Sets the given stack trace elements with the backtrace
    548      * of the given Throwable.
    549      */
    550     private static native void initStackTraceElements(StackTraceElement[] elements,
    551                                                       Throwable x);
    552     /*
    553      * Sets the given stack trace element with the given StackFrameInfo
    554      */
    555     private static native void initStackTraceElement(StackTraceElement element,
    556                                                      StackFrameInfo sfi);
    557
    558     @java.io.Serial
    559     private static final long serialVersionUID = 6992337162326171013L;
    560 }
    --- EOF ---