| /* | |
| * Copyright (c) 1994, 2025, Oracle and/or its affiliates. All rights reserved. | |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| * | |
| * This code is free software; you can redistribute it and/or modify it | |
| * under the terms of the GNU General Public License version 2 only, as | |
| * published by the Free Software Foundation. Oracle designates this | |
| * particular file as subject to the "Classpath" exception as provided | |
| * by Oracle in the LICENSE file that accompanied this code. | |
| * | |
| * This code is distributed in the hope that it will be useful, but WITHOUT | |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| * version 2 for more details (a copy is included in the LICENSE file that | |
| * accompanied this code). | |
| * | |
| * You should have received a copy of the GNU General Public License version | |
| * 2 along with this work; if not, write to the Free Software Foundation, | |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| * | |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| * or visit www.oracle.com if you need additional information or have any | |
| * questions. | |
| */ | |
| package java.lang; | |
| import java.io.*; | |
| import java.util.*; | |
| import jdk.internal.event.ThrowableTracer; | |
| /** | |
| * The {@code Throwable} class is the superclass of all errors and | |
| * exceptions in the Java language. Only objects that are instances of this | |
| * class (or one of its subclasses) are thrown by the Java Virtual Machine or | |
| * can be thrown by the Java {@code throw} statement. Similarly, only | |
| * this class or one of its subclasses can be the argument type in a | |
| * {@code catch} clause. | |
| * | |
| * For the purposes of compile-time checking of exceptions, {@code | |
| * Throwable} and any subclass of {@code Throwable} that is not also a | |
| * subclass of either {@link RuntimeException} or {@link Error} are | |
| * regarded as checked exceptions. | |
| * | |
| * <p>Instances of two subclasses, {@link java.lang.Error} and | |
| * {@link java.lang.Exception}, are conventionally used to indicate | |
| * that exceptional situations have occurred. Typically, these instances | |
| * are freshly created in the context of the exceptional situation so | |
| * as to include relevant information (such as stack trace data). | |
| * | |
| * <p>A throwable contains a snapshot of the execution stack of its | |
| * thread at the time it was created. It can also contain a message | |
| * string that gives more information about the error. Over time, a | |
| * throwable can {@linkplain Throwable#addSuppressed suppress} other | |
| * throwables from being propagated. Finally, the throwable can also | |
| * contain a <i>cause</i>: another throwable that caused this | |
| * throwable to be constructed. The recording of this causal information | |
| * is referred to as the <i>chained exception</i> facility, as the | |
| * cause can, itself, have a cause, and so on, leading to a "chain" of | |
| * exceptions, each caused by another. | |
| * | |
| * <p>One reason that a throwable may have a cause is that the class that | |
| * throws it is built atop a lower layered abstraction, and an operation on | |
| * the upper layer fails due to a failure in the lower layer. It would be bad | |
| * design to let the throwable thrown by the lower layer propagate outward, as | |
| * it is generally unrelated to the abstraction provided by the upper layer. | |
| * Further, doing so would tie the API of the upper layer to the details of | |
| * its implementation, assuming the lower layer's exception was a checked | |
| * exception. Throwing a "wrapped exception" (i.e., an exception containing a | |
| * cause) allows the upper layer to communicate the details of the failure to | |
| * its caller without incurring either of these shortcomings. It preserves | |
| * the flexibility to change the implementation of the upper layer without | |
| * changing its API (in particular, the set of exceptions thrown by its | |
| * methods). | |
| * | |
| * <p>A second reason that a throwable may have a cause is that the method | |
| * that throws it must conform to a general-purpose interface that does not | |
| * permit the method to throw the cause directly. For example, suppose | |
| * a persistent collection conforms to the {@link java.util.Collection | |
| * Collection} interface, and that its persistence is implemented atop | |
| * {@code java.io}. Suppose the internals of the {@code add} method | |
| * can throw an {@link java.io.IOException IOException}. The implementation | |
| * can communicate the details of the {@code IOException} to its caller | |
| * while conforming to the {@code Collection} interface by wrapping the | |
| * {@code IOException} in an appropriate unchecked exception. (The | |
| * specification for the persistent collection should indicate that it is | |
| * capable of throwing such exceptions.) | |
| * | |
| * <p>A cause can be associated with a throwable in two ways: via a | |
| * constructor that takes the cause as an argument, or via the | |
| * {@link #initCause(Throwable)} method. New throwable classes that | |
| * wish to allow causes to be associated with them should provide constructors | |
| * that take a cause and delegate (perhaps indirectly) to one of the | |
| * {@code Throwable} constructors that takes a cause. | |
| * | |
| * Because the {@code initCause} method is public, it allows a cause to be | |
| * associated with any throwable, even a "legacy throwable" whose | |
| * implementation predates the addition of the exception chaining mechanism to | |
| * {@code Throwable}. | |
| * | |
| * <p>By convention, class {@code Throwable} and its subclasses have two | |
| * constructors, one that takes no arguments and one that takes a | |
| * {@code String} argument that can be used to produce a detail message. | |
| * Further, those subclasses that might likely have a cause associated with | |
| * them should have two more constructors, one that takes a | |
| * {@code Throwable} (the cause), and one that takes a | |
| * {@code String} (the detail message) and a {@code Throwable} (the | |
| * cause). | |
| * | |
| * @author Josh Bloch (Added exception chaining and programmatic access to | |
| * stack trace in 1.4.) | |
| * @jls 11.2 Compile-Time Checking of Exceptions | |
| * @since 1.0 | |
| */ | |
| public class Throwable implements Serializable { | |
| /** use serialVersionUID from JDK 1.0.2 for interoperability */ | |
| @java.io.Serial | |
| private static final long serialVersionUID = -3042686055658047285L; | |
| /** | |
| * Flag set by jdk.internal.event.JFRTracing to indicate if | |
| * exceptions should be traced by JFR. | |
| */ | |
| static boolean jfrTracing; | |
| /** | |
| * The JVM saves some indication of the stack backtrace in this slot. | |
| */ | |
| private transient Object backtrace; | |
| /** | |
| * Specific details about the Throwable. For example, for | |
| * {@code FileNotFoundException}, this contains the name of | |
| * the file that could not be found. | |
| * | |
| * @serial | |
| */ | |
| private String detailMessage; | |
| /** | |
| * Holder class to defer initializing sentinel objects only used | |
| * for serialization. | |
| */ | |
| private static class SentinelHolder { | |
| /** | |
| * {@linkplain #setStackTrace(StackTraceElement[]) Setting the | |
| * stack trace} to a one-element array containing this sentinel | |
| * value indicates future attempts to set the stack trace will be | |
| * ignored. The sentinel is equal to the result of calling:<br> | |
| * {@code new StackTraceElement("", "", null, Integer.MIN_VALUE)} | |
| */ | |
| public static final StackTraceElement STACK_TRACE_ELEMENT_SENTINEL = | |
| new StackTraceElement("", "", null, Integer.MIN_VALUE); | |
| /** | |
| * Sentinel value used in the serial form to indicate an immutable | |
| * stack trace. | |
| */ | |
| public static final StackTraceElement[] STACK_TRACE_SENTINEL = | |
| new StackTraceElement[] {STACK_TRACE_ELEMENT_SENTINEL}; | |
| } | |
| /** | |
| * A shared value for an empty stack. | |
| */ | |
| private static final StackTraceElement[] UNASSIGNED_STACK = new StackTraceElement[0]; | |
| /* | |
| * To allow Throwable objects to be made immutable and safely | |
| * reused by the JVM, such as OutOfMemoryErrors, fields of | |
| * Throwable that are writable in response to user actions, cause, | |
| * stackTrace, and suppressedExceptions obey the following | |
| * protocol: | |
| * | |
| * 1) The fields are initialized to a non-null sentinel value | |
| * which indicates the value has logically not been set. | |
| * | |
| * 2) Writing a null to the field indicates further writes | |
| * are forbidden | |
| * | |
| * 3) The sentinel value may be replaced with another non-null | |
| * value. | |
| * | |
| * For example, implementations of the HotSpot JVM have | |
| * preallocated OutOfMemoryError objects to provide for better | |
| * diagnosability of that situation. These objects are created | |
| * without calling the constructor for that class and the fields | |
| * in question are initialized to null. To support this | |
| * capability, any new fields added to Throwable that require | |
| * being initialized to a non-null value require a coordinated JVM | |
| * change. | |
| */ | |
| /** | |
| * The throwable that caused this throwable to get thrown, or null if this | |
| * throwable was not caused by another throwable, or if the causative | |
| * throwable is unknown. If this field is equal to this throwable itself, | |
| * it indicates that the cause of this throwable has not yet been | |
| * initialized. | |
| * | |
| * @serial | |
| * @since 1.4 | |
| */ | |
| private Throwable cause = this; | |
| /** | |
| * The stack trace, as returned by {@link #getStackTrace()}. | |
| * | |
| * The field is initialized to a zero-length array. A {@code | |
| * null} value of this field indicates subsequent calls to {@link | |
| * #setStackTrace(StackTraceElement[])} and {@link | |
| * #fillInStackTrace()} will be no-ops. | |
| * | |
| * @serial | |
| * @since 1.4 | |
| */ | |
| private StackTraceElement[] stackTrace = UNASSIGNED_STACK; | |
| /** | |
| * The JVM code sets the depth of the backtrace for later retrieval | |
| */ | |
| private transient int depth; | |
| // Setting this static field introduces an acceptable | |
| // initialization dependency on a few java.util classes. | |
| private static final List<Throwable> SUPPRESSED_SENTINEL = Collections.emptyList(); | |
| /** | |
| * The list of suppressed exceptions, as returned by {@link | |
| * #getSuppressed()}. The list is initialized to a zero-element | |
| * unmodifiable sentinel list. When a serialized Throwable is | |
| * read in, if the {@code suppressedExceptions} field points to a | |
| * zero-element list, the field is reset to the sentinel value. | |
| * | |
| * @serial | |
| * @since 1.7 | |
| */ | |
| @SuppressWarnings("serial") // Not statically typed as Serializable | |
| private List<Throwable> suppressedExceptions = SUPPRESSED_SENTINEL; | |
| /** Message for trying to suppress a null exception. */ | |
| private static final String NULL_CAUSE_MESSAGE = "Cannot suppress a null exception."; | |
| /** Message for trying to suppress oneself. */ | |
| private static final String SELF_SUPPRESSION_MESSAGE = "Self-suppression not permitted"; | |
| /** Caption for labeling causative exception stack traces */ | |
| private static final String CAUSE_CAPTION = "Caused by: "; | |
| /** Caption for labeling suppressed exception stack traces */ | |
| private static final String SUPPRESSED_CAPTION = "Suppressed: "; | |
| /** | |
| * Constructs a new throwable with {@code null} as its detail message. | |
| * The cause is not initialized, and may subsequently be initialized by a | |
| * call to {@link #initCause}. | |
| * | |
| * <p>The {@link #fillInStackTrace()} method is called to initialize | |
| * the stack trace data in the newly created throwable. | |
| */ | |
| @SuppressWarnings("this-escape") | |
| public Throwable() { | |
| fillInStackTrace(); | |
| if (jfrTracing) { | |
| ThrowableTracer.traceThrowable(getClass(), null); | |
| } | |
| } | |
| /** | |
| * Constructs a new throwable with the specified detail message. The | |
| * cause is not initialized, and may subsequently be initialized by | |
| * a call to {@link #initCause}. | |
| * | |
| * <p>The {@link #fillInStackTrace()} method is called to initialize | |
| * the stack trace data in the newly created throwable. | |
| * | |
| * @param message the detail message. The detail message is saved for | |
| * later retrieval by the {@link #getMessage()} method. | |
| */ | |
| @SuppressWarnings("this-escape") | |
| public Throwable(String message) { | |
| fillInStackTrace(); | |
| detailMessage = message; | |
| if (jfrTracing) { | |
| ThrowableTracer.traceThrowable(getClass(), message); | |
| } | |
| } | |
| /** | |
| * Constructs a new throwable with the specified detail message and | |
| * cause. <p>Note that the detail message associated with | |
| * {@code cause} is <i>not</i> automatically incorporated in | |
| * this throwable's detail message. | |
| * | |
| * <p>The {@link #fillInStackTrace()} method is called to initialize | |
| * the stack trace data in the newly created throwable. | |
| * | |
| * @param message the detail message (which is saved for later retrieval | |
| * by the {@link #getMessage()} method). | |
| * @param cause the cause (which is saved for later retrieval by the | |
| * {@link #getCause()} method). (A {@code null} value is | |
| * permitted, and indicates that the cause is nonexistent or | |
| * unknown.) | |
| * @since 1.4 | |
| */ | |
| @SuppressWarnings("this-escape") | |
| public Throwable(String message, Throwable cause) { | |
| fillInStackTrace(); | |
| detailMessage = message; | |
| this.cause = cause; | |
| if (jfrTracing) { | |
| ThrowableTracer.traceThrowable(getClass(), message); | |
| } | |
| } | |
| /** | |
| * Constructs a new throwable with the specified cause and a detail | |
| * message of {@code (cause==null ? null : cause.toString())} (which | |
| * typically contains the class and detail message of {@code cause}). | |
| * This constructor is useful for throwables that are little more than | |
| * wrappers for other throwables (for example, {@link | |
| * java.security.PrivilegedActionException}). | |
| * | |
| * <p>The {@link #fillInStackTrace()} method is called to initialize | |
| * the stack trace data in the newly created throwable. | |
| * | |
| * @param cause the cause (which is saved for later retrieval by the | |
| * {@link #getCause()} method). (A {@code null} value is | |
| * permitted, and indicates that the cause is nonexistent or | |
| * unknown.) | |
| * @since 1.4 | |
| */ | |
| @SuppressWarnings("this-escape") | |
| public Throwable(Throwable cause) { | |
| fillInStackTrace(); | |
| detailMessage = (cause==null ? null : cause.toString()); | |
| this.cause = cause; | |
| if (jfrTracing) { | |
| ThrowableTracer.traceThrowable(getClass(), null); | |
| } | |
| } | |
| /** | |
| * Constructs a new throwable with the specified detail message, | |
| * cause, {@linkplain #addSuppressed suppression} enabled or | |
| * disabled, and writable stack trace enabled or disabled. If | |
| * suppression is disabled, {@link #getSuppressed} for this object | |
| * will return a zero-length array and calls to {@link | |
| * #addSuppressed} that would otherwise append an exception to the | |
| * suppressed list will have no effect. If the writable stack | |
| * trace is false, this constructor will not call {@link | |
| * #fillInStackTrace()}, a {@code null} will be written to the | |
| * {@code stackTrace} field, and subsequent calls to {@code | |
| * fillInStackTrace} and {@link | |
| * #setStackTrace(StackTraceElement[])} will not set the stack | |
| * trace. If the writable stack trace is false, {@link | |
| * #getStackTrace} will return a zero length array. | |
| * | |
| * <p>Note that the other constructors of {@code Throwable} treat | |
| * suppression as being enabled and the stack trace as being | |
| * writable. Subclasses of {@code Throwable} should document any | |
| * conditions under which suppression is disabled and document | |
| * conditions under which the stack trace is not writable. | |
| * Disabling of suppression should only occur in exceptional | |
| * circumstances where special requirements exist, such as a | |
| * virtual machine reusing exception objects under low-memory | |
| * situations. Circumstances where a given exception object is | |
| * repeatedly caught and rethrown, such as to implement control | |
| * flow between two sub-systems, is another situation where | |
| * immutable throwable objects would be appropriate. | |
| * | |
| * @param message the detail message. | |
| * @param cause the cause. (A {@code null} value is permitted, | |
| * and indicates that the cause is nonexistent or unknown.) | |
| * @param enableSuppression whether or not suppression is enabled | |
| * @param writableStackTrace whether or not the stack trace is writable | |
| * | |
| * @see OutOfMemoryError | |
| * @see NullPointerException | |
| * @see ArithmeticException | |
| * @since 1.7 | |
| */ | |
| @SuppressWarnings("this-escape") | |
| protected Throwable(String message, Throwable cause, | |
| boolean enableSuppression, | |
| boolean writableStackTrace) { | |
| if (writableStackTrace) { | |
| fillInStackTrace(); | |
| } else { | |
| stackTrace = null; | |
| } | |
| detailMessage = message; | |
| this.cause = cause; | |
| if (!enableSuppression) { | |
| suppressedExceptions = null; | |
| } | |
| if (jfrTracing) { | |
| ThrowableTracer.traceThrowable(getClass(), message); | |
| } | |
| } | |
| /** | |
| * Returns the detail message string of this throwable. | |
| * | |
| * @return the detail message string of this {@code Throwable} instance | |
| * (which may be {@code null}). | |
| */ | |
| public String getMessage() { | |
| return detailMessage; | |
| } | |
| /** | |
| * Creates a localized description of this throwable. | |
| * Subclasses may override this method in order to produce a | |
| * locale-specific message. For subclasses that do not override this | |
| * method, the default implementation returns the same result as | |
| * {@code getMessage()}. | |
| * | |
| * @return The localized description of this throwable. | |
| * @since 1.1 | |
| */ | |
| public String getLocalizedMessage() { | |
| return getMessage(); | |
| } | |
| /** | |
| * Returns the cause of this throwable or {@code null} if the | |
| * cause is nonexistent or unknown. (The cause is the throwable that | |
| * caused this throwable to get thrown.) | |
| * | |
| * <p>This implementation returns the cause that was supplied via one of | |
| * the constructors requiring a {@code Throwable}, or that was set after | |
| * creation with the {@link #initCause(Throwable)} method. While it is | |
| * typically unnecessary to override this method, a subclass can override | |
| * it to return a cause set by some other means. This is appropriate for | |
| * a "legacy chained throwable" that predates the addition of chained | |
| * exceptions to {@code Throwable}. Note that it is <i>not</i> | |
| * necessary to override any of the {@code PrintStackTrace} methods, | |
| * all of which invoke the {@code getCause} method to determine the | |
| * cause of a throwable. | |
| * | |
| * @return the cause of this throwable or {@code null} if the | |
| * cause is nonexistent or unknown. | |
| * @since 1.4 | |
| */ | |
| public synchronized Throwable getCause() { | |
| return (cause==this ? null : cause); | |
| } | |
| /** | |
| * Initializes the <i>cause</i> of this throwable to the specified value. | |
| * (The cause is the throwable that caused this throwable to get thrown.) | |
| * | |
| * <p>This method can be called at most once. It is generally called from | |
| * within the constructor, or immediately after creating the | |
| * throwable. If this throwable was created | |
| * with {@link #Throwable(Throwable)} or | |
| * {@link #Throwable(String,Throwable)}, this method cannot be called | |
| * even once. | |
| * | |
| * <p>An example of using this method on a legacy throwable type | |
| * without other support for setting the cause is: | |
| * | |
| * <pre> | |
| * try { | |
| * lowLevelOp(); | |
| * } catch (LowLevelException le) { | |
| * throw (HighLevelException) | |
| * new HighLevelException().initCause(le); // Legacy constructor | |
| * } | |
| * </pre> | |
| * | |
| * @param cause the cause (which is saved for later retrieval by the | |
| * {@link #getCause()} method). (A {@code null} value is | |
| * permitted, and indicates that the cause is nonexistent or | |
| * unknown.) | |
| * @return a reference to this {@code Throwable} instance. | |
| * @throws IllegalArgumentException if {@code cause} is this | |
| * throwable. (A throwable cannot be its own cause.) | |
| * @throws IllegalStateException if this throwable was | |
| * created with {@link #Throwable(Throwable)} or | |
| * {@link #Throwable(String,Throwable)}, or this method has already | |
| * been called on this throwable. | |
| * @since 1.4 | |
| */ | |
| public synchronized Throwable initCause(Throwable cause) { | |
| if (this.cause != this) | |
| throw new IllegalStateException("Can't overwrite cause with " + | |
| Objects.toString(cause, "a null"), this); | |
| if (cause == this) | |
| throw new IllegalArgumentException("Self-causation not permitted", this); | |
| this.cause = cause; | |
| return this; | |
| } | |
| /* | |
| * This is called by readObject of a few exceptions such as | |
| * ClassNotFoundException and ExceptionInInitializerError to deserialize | |
| * a stream output from an older runtime version where the cause may | |
| * have set to null. | |
| */ | |
| final void setCause(Throwable t) { | |
| this.cause = t; | |
| } | |
| /** | |
| * Returns a short description of this throwable. | |
| * The result is the concatenation of: | |
| * <ul> | |
| * <li> the {@linkplain Class#getName() name} of the class of this object | |
| * <li> ": " (a colon and a space) | |
| * <li> the result of invoking this object's {@link #getLocalizedMessage} | |
| * method | |
| * </ul> | |
| * If {@code getLocalizedMessage} returns {@code null}, then just | |
| * the class name is returned. | |
| * | |
| * @return a string representation of this throwable. | |
| */ | |
| public String toString() { | |
| String s = getClass().getName(); | |
| String message = getLocalizedMessage(); | |
| return (message != null) ? (s + ": " + message) : s; | |
| } | |
| /** | |
| * Prints this throwable and its backtrace to the | |
| * standard error stream. This method prints a stack trace for this | |
| * {@code Throwable} object on the error output stream that is | |
| * the value of the field {@code System.err}. The first line of | |
| * output contains the result of the {@link #toString()} method for | |
| * this object. Remaining lines represent data previously recorded by | |
| * the method {@link #fillInStackTrace()}. The format of this | |
| * information depends on the implementation, but the following | |
| * example may be regarded as typical: | |
| * <blockquote><pre> | |
| * java.lang.NullPointerException | |
| * at MyClass.mash(MyClass.java:9) | |
| * at MyClass.crunch(MyClass.java:6) | |
| * at MyClass.main(MyClass.java:3) | |
| * </pre></blockquote> | |
| * This example was produced by running the program: | |
| * <pre> | |
| * class MyClass { | |
| * public static void main(String[] args) { | |
| * crunch(null); | |
| * } | |
| * static void crunch(int[] a) { | |
| * mash(a); | |
| * } | |
| * static void mash(int[] b) { | |
| * System.out.println(b[0]); | |
| * } | |
| * } | |
| * </pre> | |
| * The backtrace for a throwable with an initialized, non-null cause | |
| * should generally include the backtrace for the cause. The format | |
| * of this information depends on the implementation, but the following | |
| * example may be regarded as typical: | |
| * <pre> | |
| * HighLevelException: MidLevelException: LowLevelException | |
| * at Junk.a(Junk.java:13) | |
| * at Junk.main(Junk.java:4) | |
| * Caused by: MidLevelException: LowLevelException | |
| * at Junk.c(Junk.java:23) | |
| * at Junk.b(Junk.java:17) | |
| * at Junk.a(Junk.java:11) | |
| * ... 1 more | |
| * Caused by: LowLevelException | |
| * at Junk.e(Junk.java:30) | |
| * at Junk.d(Junk.java:27) | |
| * at Junk.c(Junk.java:21) | |
| * ... 3 more | |
| * </pre> | |
| * Note the presence of lines containing the characters {@code "..."}. | |
| * These lines indicate that the remainder of the stack trace for this | |
| * exception matches the indicated number of frames from the bottom of the | |
| * stack trace of the exception that was caused by this exception (the | |
| * "enclosing" exception). This shorthand can greatly reduce the length | |
| * of the output in the common case where a wrapped exception is thrown | |
| * from the same method as the "causative exception" is caught. The above | |
| * example was produced by running the program: | |
| * <pre> | |
| * public class Junk { | |
| * public static void main(String args[]) { | |
| * try { | |
| * a(); | |
| * } catch(HighLevelException e) { | |
| * e.printStackTrace(); | |
| * } | |
| * } | |
| * static void a() throws HighLevelException { | |
| * try { | |
| * b(); | |
| * } catch(MidLevelException e) { | |
| * throw new HighLevelException(e); | |
| * } | |
| * } | |
| * static void b() throws MidLevelException { | |
| * c(); | |
| * } | |
| * static void c() throws MidLevelException { | |
| * try { | |
| * d(); | |
| * } catch(LowLevelException e) { | |
| * throw new MidLevelException(e); | |
| * } | |
| * } | |
| * static void d() throws LowLevelException { | |
| * e(); | |
| * } | |
| * static void e() throws LowLevelException { | |
| * throw new LowLevelException(); | |
| * } | |
| * } | |
| * | |
| * class HighLevelException extends Exception { | |
| * HighLevelException(Throwable cause) { super(cause); } | |
| * } | |
| * | |
| * class MidLevelException extends Exception { | |
| * MidLevelException(Throwable cause) { super(cause); } | |
| * } | |
| * | |
| * class LowLevelException extends Exception { | |
| * } | |
| * </pre> | |
| * As of release 7, the platform supports the notion of | |
| * <i>suppressed exceptions</i> (in conjunction with the {@code | |
| * try}-with-resources statement). Any exceptions that were | |
| * suppressed in order to deliver an exception are printed out | |
| * beneath the stack trace. The format of this information | |
| * depends on the implementation, but the following example may be | |
| * regarded as typical: | |
| * | |
| * <pre> | |
| * Exception in thread "main" java.lang.Exception: Something happened | |
| * at Foo.bar(Foo.java:10) | |
| * at Foo.main(Foo.java:5) | |
| * Suppressed: Resource$CloseFailException: Resource ID = 0 | |
| * at Resource.close(Resource.java:26) | |
| * at Foo.bar(Foo.java:9) | |
| * ... 1 more | |
| * </pre> | |
| * Note that the "... n more" notation is used on suppressed exceptions | |
| * just as it is used on causes. Unlike causes, suppressed exceptions are | |
| * indented beyond their "containing exceptions." | |
| * | |
| * <p>An exception can have both a cause and one or more suppressed | |
| * exceptions: | |
| * <pre> | |
| * Exception in thread "main" java.lang.Exception: Main block | |
| * at Foo3.main(Foo3.java:7) | |
| * Suppressed: Resource$CloseFailException: Resource ID = 2 | |
| * at Resource.close(Resource.java:26) | |
| * at Foo3.main(Foo3.java:5) | |
| * Suppressed: Resource$CloseFailException: Resource ID = 1 | |
| * at Resource.close(Resource.java:26) | |
| * at Foo3.main(Foo3.java:5) | |
| * Caused by: java.lang.Exception: I did it | |
| * at Foo3.main(Foo3.java:8) | |
| * </pre> | |
| * Likewise, a suppressed exception can have a cause: | |
| * <pre> | |
| * Exception in thread "main" java.lang.Exception: Main block | |
| * at Foo4.main(Foo4.java:6) | |
| * Suppressed: Resource2$CloseFailException: Resource ID = 1 | |
| * at Resource2.close(Resource2.java:20) | |
| * at Foo4.main(Foo4.java:5) | |
| * Caused by: java.lang.Exception: Rats, you caught me | |
| * at Resource2$CloseFailException.<init>(Resource2.java:45) | |
| * ... 2 more | |
| * </pre> | |
| */ | |
| public void printStackTrace() { | |
| printStackTrace(System.err); | |
| } | |
| /** | |
| * Prints this throwable and its backtrace to the specified print stream. | |
| * | |
| * @param s {@code PrintStream} to use for output | |
| */ | |
| public void printStackTrace(PrintStream s) { | |
| printStackTrace(new WrappedPrintStream(s)); | |
| } | |
| private void printStackTrace(PrintStreamOrWriter s) { | |
| // Guard against malicious overrides of Throwable.equals by | |
| // using a Set with identity equality semantics. | |
| Set<Throwable> dejaVu = Collections.newSetFromMap(new IdentityHashMap<>()); | |
| dejaVu.add(this); | |
| synchronized(s.lock()) { | |
| // Print our stack trace | |
| s.println(this); | |
| StackTraceElement[] trace = getOurStackTrace(); | |
| for (StackTraceElement traceElement : trace) | |
| s.println("\tat " + traceElement); | |
| // Print suppressed exceptions, if any | |
| for (Throwable se : getSuppressed()) | |
| se.printEnclosedStackTrace(s, trace, SUPPRESSED_CAPTION, "\t", dejaVu); | |
| // Print cause, if any | |
| Throwable ourCause = getCause(); | |
| if (ourCause != null) | |
| ourCause.printEnclosedStackTrace(s, trace, CAUSE_CAPTION, "", dejaVu); | |
| } | |
| } | |
| /** | |
| * Print our stack trace as an enclosed exception for the specified | |
| * stack trace. | |
| */ | |
| private void printEnclosedStackTrace(PrintStreamOrWriter s, | |
| StackTraceElement[] enclosingTrace, | |
| String caption, | |
| String prefix, | |
| Set<Throwable> dejaVu) { | |
| assert Thread.holdsLock(s.lock()); | |
| if (dejaVu.contains(this)) { | |
| s.println(prefix + caption + "[CIRCULAR REFERENCE: " + this + "]"); | |
| } else { | |
| dejaVu.add(this); | |
| // Compute number of frames in common between this and enclosing trace | |
| StackTraceElement[] trace = getOurStackTrace(); | |
| int m = trace.length - 1; | |
| int n = enclosingTrace.length - 1; | |
| while (m >= 0 && n >=0 && trace[m].equals(enclosingTrace[n])) { | |
| m--; n--; | |
| } | |
| int framesInCommon = trace.length - 1 - m; | |
| // Print our stack trace | |
| s.println(prefix + caption + this); | |
| for (int i = 0; i <= m; i++) | |
| s.println(prefix + "\tat " + trace[i]); | |
| if (framesInCommon != 0) | |
| s.println(prefix + "\t... " + framesInCommon + " more"); | |
| // Print suppressed exceptions, if any | |
| for (Throwable se : getSuppressed()) | |
| se.printEnclosedStackTrace(s, trace, SUPPRESSED_CAPTION, | |
| prefix +"\t", dejaVu); | |
| // Print cause, if any | |
| Throwable ourCause = getCause(); | |
| if (ourCause != null) | |
| ourCause.printEnclosedStackTrace(s, trace, CAUSE_CAPTION, prefix, dejaVu); | |
| } | |
| } | |
| /** | |
| * Prints this throwable and its backtrace to the specified | |
| * print writer. | |
| * | |
| * @param s {@code PrintWriter} to use for output | |
| * @since 1.1 | |
| */ | |
| public void printStackTrace(PrintWriter s) { | |
| printStackTrace(new WrappedPrintWriter(s)); | |
| } | |
| /** | |
| * Wrapper class for PrintStream and PrintWriter to enable a single | |
| * implementation of printStackTrace. | |
| */ | |
| private abstract static class PrintStreamOrWriter { | |
| /** Returns the object to be locked when using this StreamOrWriter */ | |
| abstract Object lock(); | |
| /** Prints the specified string as a line on this StreamOrWriter */ | |
| abstract void println(Object o); | |
| } | |
| private static class WrappedPrintStream extends PrintStreamOrWriter { | |
| private final PrintStream printStream; | |
| WrappedPrintStream(PrintStream printStream) { | |
| this.printStream = printStream; | |
| } | |
| Object lock() { | |
| return printStream; | |
| } | |
| void println(Object o) { | |
| printStream.println(o); | |
| } | |
| } | |
| private static class WrappedPrintWriter extends PrintStreamOrWriter { | |
| private final PrintWriter printWriter; | |
| WrappedPrintWriter(PrintWriter printWriter) { | |
| this.printWriter = printWriter; | |
| } | |
| Object lock() { | |
| return printWriter; | |
| } | |
| void println(Object o) { | |
| printWriter.println(o); | |
| } | |
| } | |
| /** | |
| * Fills in the execution stack trace. This method records within this | |
| * {@code Throwable} object information about the current state of | |
| * the stack frames for the current thread. | |
| * | |
| * <p>If the stack trace of this {@code Throwable} {@linkplain | |
| * Throwable#Throwable(String, Throwable, boolean, boolean) is not | |
| * writable}, calling this method has no effect. | |
| * | |
| * @return a reference to this {@code Throwable} instance. | |
| * @see java.lang.Throwable#printStackTrace() | |
| */ | |
| public synchronized Throwable fillInStackTrace() { | |
| if (stackTrace != null || | |
| backtrace != null /* Out of protocol state */ ) { | |
| fillInStackTrace(0); | |
| stackTrace = UNASSIGNED_STACK; | |
| } | |
| return this; | |
| } | |
| private native Throwable fillInStackTrace(int dummy); | |
| /** | |
| * Provides programmatic access to the stack trace information printed by | |
| * {@link #printStackTrace()}. Returns an array of stack trace elements, | |
| * each representing one stack frame. The zeroth element of the array | |
| * (assuming the array's length is non-zero) represents the top of the | |
| * stack, which is the last method invocation in the sequence. Typically, | |
| * this is the point at which this throwable was created and thrown. | |
| * The last element of the array (assuming the array's length is non-zero) | |
| * represents the bottom of the stack, which is the first method invocation | |
| * in the sequence. | |
| * | |
| * <p>Some virtual machines may, under some circumstances, omit one | |
| * or more stack frames from the stack trace. In the extreme case, | |
| * a virtual machine that has no stack trace information concerning | |
| * this throwable is permitted to return a zero-length array from this | |
| * method. Generally speaking, the array returned by this method will | |
| * contain one element for every frame that would be printed by | |
| * {@code printStackTrace}. Writes to the returned array do not | |
| * affect future calls to this method. | |
| * | |
| * @return an array of stack trace elements representing the stack trace | |
| * pertaining to this throwable. | |
| * @since 1.4 | |
| */ | |
| public StackTraceElement[] getStackTrace() { | |
| return getOurStackTrace().clone(); | |
| } | |
| private synchronized StackTraceElement[] getOurStackTrace() { | |
| // Initialize stack trace field with information from | |
| // backtrace if this is the first call to this method | |
| if (stackTrace == UNASSIGNED_STACK || stackTrace == null) { | |
| if (backtrace != null) { /* Out of protocol state */ | |
| stackTrace = StackTraceElement.of(backtrace, depth); | |
| } else { | |
| // no backtrace, fillInStackTrace overridden or not called | |
| return UNASSIGNED_STACK; | |
| } | |
| } | |
| return stackTrace; | |
| } | |
| /** | |
| * Sets the stack trace elements that will be returned by | |
| * {@link #getStackTrace()} and printed by {@link #printStackTrace()} | |
| * and related methods. | |
| * | |
| * This method, which is designed for use by RPC frameworks and other | |
| * advanced systems, allows the client to override the default | |
| * stack trace that is either generated by {@link #fillInStackTrace()} | |
| * when a throwable is constructed or deserialized when a throwable is | |
| * read from a serialization stream. | |
| * | |
| * <p>If the stack trace of this {@code Throwable} {@linkplain | |
| * Throwable#Throwable(String, Throwable, boolean, boolean) is not | |
| * writable}, calling this method has no effect other than | |
| * validating its argument. | |
| * | |
| * @param stackTrace the stack trace elements to be associated with | |
| * this {@code Throwable}. The specified array is copied by this | |
| * call; changes in the specified array after the method invocation | |
| * returns will have no effect on this {@code Throwable}'s stack | |
| * trace. | |
| * | |
| * @throws NullPointerException if {@code stackTrace} is | |
| * {@code null} or if any of the elements of | |
| * {@code stackTrace} are {@code null} | |
| * | |
| * @since 1.4 | |
| */ | |
| public void setStackTrace(StackTraceElement[] stackTrace) { | |
| // Validate argument | |
| StackTraceElement[] defensiveCopy = stackTrace.clone(); | |
| for (int i = 0; i < defensiveCopy.length; i++) { | |
| if (defensiveCopy[i] == null) | |
| throw new NullPointerException("stackTrace[" + i + "]"); | |
| } | |
| synchronized (this) { | |
| if (this.stackTrace == null && // Immutable stack | |
| backtrace == null) // Test for out of protocol state | |
| return; | |
| this.stackTrace = defensiveCopy; | |
| } | |
| } | |
| /** | |
| * Reads a {@code Throwable} from a stream, enforcing | |
| * well-formedness constraints on fields. Null entries and | |
| * self-pointers are not allowed in the list of {@code | |
| * suppressedExceptions}. Null entries are not allowed for stack | |
| * trace elements. A null stack trace in the serial form results | |
| * in a zero-length stack element array. A single-element stack | |
| * trace whose entry is equal to {@code new StackTraceElement("", | |
| * "", null, Integer.MIN_VALUE)} results in a {@code null} {@code | |
| * stackTrace} field. | |
| * | |
| * Note that there are no constraints on the value the {@code | |
| * cause} field can hold; both {@code null} and {@code this} are | |
| * valid values for the field. | |
| * | |
| * @param s the {@code ObjectInputStream} from which data is read | |
| * @throws IOException if an I/O error occurs | |
| * @throws ClassNotFoundException if a serialized class cannot be loaded | |
| */ | |
| @java.io.Serial | |
| private void readObject(ObjectInputStream s) | |
| throws IOException, ClassNotFoundException { | |
| s.defaultReadObject(); // read in all fields | |
| // Set suppressed exceptions and stack trace elements fields | |
| // to marker values until the contents from the serial stream | |
| // are validated. | |
| List<Throwable> candidateSuppressedExceptions = suppressedExceptions; | |
| suppressedExceptions = SUPPRESSED_SENTINEL; | |
| StackTraceElement[] candidateStackTrace = stackTrace; | |
| stackTrace = UNASSIGNED_STACK.clone(); | |
| if (candidateSuppressedExceptions != null) { | |
| int suppressedSize = validateSuppressedExceptionsList(candidateSuppressedExceptions); | |
| if (suppressedSize > 0) { // Copy valid Throwables to new list | |
| var suppList = new ArrayList<Throwable>(Math.min(100, suppressedSize)); | |
| for (Throwable t : candidateSuppressedExceptions) { | |
| // Enforce constraints on suppressed exceptions in | |
| // case of corrupt or malicious stream. | |
| Objects.requireNonNull(t, NULL_CAUSE_MESSAGE); | |
| if (t == this) | |
| throw new IllegalArgumentException(SELF_SUPPRESSION_MESSAGE); | |
| suppList.add(t); | |
| } | |
| // If there are any invalid suppressed exceptions, | |
| // implicitly use the sentinel value assigned earlier. | |
| suppressedExceptions = suppList; | |
| } | |
| } else { | |
| suppressedExceptions = null; | |
| } | |
| /* | |
| * For zero-length stack traces, use a clone of | |
| * UNASSIGNED_STACK rather than UNASSIGNED_STACK itself to | |
| * allow identity comparison against UNASSIGNED_STACK in | |
| * getOurStackTrace. The identity of UNASSIGNED_STACK in | |
| * stackTrace indicates to the getOurStackTrace method that | |
| * the stackTrace needs to be constructed from the information | |
| * in backtrace. | |
| */ | |
| if (candidateStackTrace != null) { | |
| // Work from a clone of the candidateStackTrace to ensure | |
| // consistency of checks. | |
| candidateStackTrace = candidateStackTrace.clone(); | |
| if (candidateStackTrace.length >= 1) { | |
| if (candidateStackTrace.length == 1 && | |
| // Check for the marker of an immutable stack trace | |
| SentinelHolder.STACK_TRACE_ELEMENT_SENTINEL.equals(candidateStackTrace[0])) { | |
| stackTrace = null; | |
| } else { // Verify stack trace elements are non-null. | |
| for (StackTraceElement ste : candidateStackTrace) { | |
| Objects.requireNonNull(ste, "null StackTraceElement in serial stream."); | |
| } | |
| stackTrace = candidateStackTrace; | |
| } | |
| } | |
| } | |
| // A null stackTrace field in the serial form can result from | |
| // an exception serialized without that field in older JDK | |
| // releases; treat such exceptions as having empty stack | |
| // traces by leaving stackTrace assigned to a clone of | |
| // UNASSIGNED_STACK. | |
| } | |
| private int validateSuppressedExceptionsList(List<Throwable> deserSuppressedExceptions) | |
| throws IOException { | |
| if (!Object.class.getModule(). | |
| equals(deserSuppressedExceptions.getClass().getModule())) { | |
| throw new StreamCorruptedException("List implementation not in base module."); | |
| } else { | |
| int size = deserSuppressedExceptions.size(); | |
| if (size < 0) { | |
| throw new StreamCorruptedException("Negative list size reported."); | |
| } | |
| return size; | |
| } | |
| } | |
| /** | |
| * Write a {@code Throwable} object to a stream. | |
| * | |
| * A {@code null} stack trace field is represented in the serial | |
| * form as a one-element array whose element is equal to {@code | |
| * new StackTraceElement("", "", null, Integer.MIN_VALUE)}. | |
| * | |
| * @param s the {@code ObjectOutputStream} to which data is written | |
| * @throws IOException if an I/O error occurs | |
| */ | |
| @java.io.Serial | |
| private synchronized void writeObject(ObjectOutputStream s) | |
| throws IOException { | |
| // Ensure that the stackTrace field is initialized to a | |
| // non-null value, if appropriate. As of JDK 7, a null stack | |
| // trace field is a valid value indicating the stack trace | |
| // should not be set. | |
| getOurStackTrace(); | |
| StackTraceElement[] oldStackTrace = stackTrace; | |
| try { | |
| if (stackTrace == null) | |
| stackTrace = SentinelHolder.STACK_TRACE_SENTINEL; | |
| s.defaultWriteObject(); | |
| } finally { | |
| stackTrace = oldStackTrace; | |
| } | |
| } | |
| /** | |
| * Appends the specified exception to the exceptions that were | |
| * suppressed in order to deliver this exception. This method is | |
| * thread-safe and typically called (automatically and implicitly) | |
| * by the {@code try}-with-resources statement. | |
| * | |
| * <p>The suppression behavior is enabled <em>unless</em> disabled | |
| * {@linkplain #Throwable(String, Throwable, boolean, boolean) via | |
| * a constructor}. When suppression is disabled, this method does | |
| * nothing other than to validate its argument. | |
| * | |
| * <p>Note that when one exception {@linkplain | |
| * #initCause(Throwable) causes} another exception, the first | |
| * exception is usually caught and then the second exception is | |
| * thrown in response. In other words, there is a causal | |
| * connection between the two exceptions. | |
| * | |
| * In contrast, there are situations where two independent | |
| * exceptions can be thrown in sibling code blocks, in particular | |
| * in the {@code try} block of a {@code try}-with-resources | |
| * statement and the compiler-generated {@code finally} block | |
| * which closes the resource. | |
| * | |
| * In these situations, only one of the thrown exceptions can be | |
| * propagated. In the {@code try}-with-resources statement, when | |
| * there are two such exceptions, the exception originating from | |
| * the {@code try} block is propagated and the exception from the | |
| * {@code finally} block is added to the list of exceptions | |
| * suppressed by the exception from the {@code try} block. As an | |
| * exception unwinds the stack, it can accumulate multiple | |
| * suppressed exceptions. | |
| * | |
| * <p>An exception may have suppressed exceptions while also being | |
| * caused by another exception. Whether or not an exception has a | |
| * cause is semantically known at the time of its creation, unlike | |
| * whether or not an exception will suppress other exceptions | |
| * which is typically only determined after an exception is | |
| * thrown. | |
| * | |
| * <p>Note that programmer written code is also able to take | |
| * advantage of calling this method in situations where there are | |
| * multiple sibling exceptions and only one can be propagated. | |
| * | |
| * @param exception the exception to be added to the list of | |
| * suppressed exceptions | |
| * @throws IllegalArgumentException if {@code exception} is this | |
| * throwable; a throwable cannot suppress itself. | |
| * @throws NullPointerException if {@code exception} is {@code null} | |
| * @since 1.7 | |
| */ | |
| public final synchronized void addSuppressed(Throwable exception) { | |
| if (exception == this) | |
| throw new IllegalArgumentException(SELF_SUPPRESSION_MESSAGE, exception); | |
| Objects.requireNonNull(exception, NULL_CAUSE_MESSAGE); | |
| if (suppressedExceptions == null) // Suppressed exceptions not recorded | |
| return; | |
| if (suppressedExceptions == SUPPRESSED_SENTINEL) | |
| suppressedExceptions = new ArrayList<>(1); | |
| suppressedExceptions.add(exception); | |
| } | |
| private static final Throwable[] EMPTY_THROWABLE_ARRAY = new Throwable[0]; | |
| /** | |
| * Returns an array containing all of the exceptions that were | |
| * suppressed, typically by the {@code try}-with-resources | |
| * statement, in order to deliver this exception. | |
| * | |
| * If no exceptions were suppressed or {@linkplain | |
| * #Throwable(String, Throwable, boolean, boolean) suppression is | |
| * disabled}, an empty array is returned. This method is | |
| * thread-safe. Writes to the returned array do not affect future | |
| * calls to this method. | |
| * | |
| * @return an array containing all of the exceptions that were | |
| * suppressed to deliver this exception. | |
| * @since 1.7 | |
| */ | |
| public final synchronized Throwable[] getSuppressed() { | |
| if (suppressedExceptions == SUPPRESSED_SENTINEL || | |
| suppressedExceptions == null) | |
| return EMPTY_THROWABLE_ARRAY; | |
| else | |
| return suppressedExceptions.toArray(EMPTY_THROWABLE_ARRAY); | |
| } | |
| } |