628 lines
26 KiB
Java
628 lines
26 KiB
Java
/*
|
|
* Copyright (c) 2015, 2021, 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 jdk.internal.reflect.CallerSensitive;
|
|
|
|
import java.lang.invoke.MethodType;
|
|
import java.util.EnumSet;
|
|
import java.util.Objects;
|
|
import java.util.Set;
|
|
import java.util.function.Consumer;
|
|
import java.util.function.Function;
|
|
import java.util.stream.Stream;
|
|
|
|
/**
|
|
* A stack walker.
|
|
*
|
|
* <p> The {@link StackWalker#walk walk} method opens a sequential stream
|
|
* of {@link StackFrame StackFrame}s for the current thread and then applies
|
|
* the given function to walk the {@code StackFrame} stream.
|
|
* The stream reports stack frame elements in order, from the top most frame
|
|
* that represents the execution point at which the stack was generated to
|
|
* the bottom most frame.
|
|
* The {@code StackFrame} stream is closed when the {@code walk} method returns.
|
|
* If an attempt is made to reuse the closed stream,
|
|
* {@code IllegalStateException} will be thrown.
|
|
*
|
|
* <p> The {@linkplain Option <em>stack walking options</em>} of a
|
|
* {@code StackWalker} determines the information of
|
|
* {@link StackFrame StackFrame} objects to be returned.
|
|
* By default, stack frames of the reflection API and implementation
|
|
* classes are {@linkplain Option#SHOW_HIDDEN_FRAMES hidden}
|
|
* and {@code StackFrame}s have the class name and method name
|
|
* available but not the {@link StackFrame#getDeclaringClass() Class reference}.
|
|
*
|
|
* <p> {@code StackWalker} is thread-safe. Multiple threads can share
|
|
* a single {@code StackWalker} object to traverse its own stack.
|
|
* A permission check is performed when a {@code StackWalker} is created,
|
|
* according to the options it requests.
|
|
* No further permission check is done at stack walking time.
|
|
*
|
|
* @apiNote
|
|
* Examples
|
|
*
|
|
* <p>1. To find the first caller filtering a known list of implementation class:
|
|
* <pre>{@code
|
|
* StackWalker walker = StackWalker.getInstance(Option.RETAIN_CLASS_REFERENCE);
|
|
* Optional<Class<?>> callerClass = walker.walk(s ->
|
|
* s.map(StackFrame::getDeclaringClass)
|
|
* .filter(interestingClasses::contains)
|
|
* .findFirst());
|
|
* }</pre>
|
|
*
|
|
* <p>2. To snapshot the top 10 stack frames of the current thread,
|
|
* <pre>{@code
|
|
* List<StackFrame> stack = StackWalker.getInstance().walk(s ->
|
|
* s.limit(10).collect(Collectors.toList()));
|
|
* }</pre>
|
|
*
|
|
* Unless otherwise noted, passing a {@code null} argument to a
|
|
* constructor or method in this {@code StackWalker} class
|
|
* will cause a {@link NullPointerException NullPointerException}
|
|
* to be thrown.
|
|
*
|
|
* @since 9
|
|
*/
|
|
public final class StackWalker {
|
|
/**
|
|
* A {@code StackFrame} object represents a method invocation returned by
|
|
* {@link StackWalker}.
|
|
*
|
|
* <p> The {@link #getDeclaringClass()} method may be unsupported as determined
|
|
* by the {@linkplain Option stack walking options} of a {@linkplain
|
|
* StackWalker stack walker}.
|
|
*
|
|
* @since 9
|
|
* @jvms 2.6
|
|
*/
|
|
public interface StackFrame {
|
|
/**
|
|
* Gets the <a href="ClassLoader.html#binary-name">binary name</a>
|
|
* of the declaring class of the method represented by this stack frame.
|
|
*
|
|
* @return the binary name of the declaring class of the method
|
|
* represented by this stack frame
|
|
*
|
|
* @jls 13.1 The Form of a Binary
|
|
*/
|
|
public String getClassName();
|
|
|
|
/**
|
|
* Gets the name of the method represented by this stack frame.
|
|
* @return the name of the method represented by this stack frame
|
|
*/
|
|
public String getMethodName();
|
|
|
|
/**
|
|
* Gets the declaring {@code Class} for the method represented by
|
|
* this stack frame.
|
|
*
|
|
* @return the declaring {@code Class} of the method represented by
|
|
* this stack frame
|
|
*
|
|
* @throws UnsupportedOperationException if this {@code StackWalker}
|
|
* is not configured with {@link Option#RETAIN_CLASS_REFERENCE
|
|
* Option.RETAIN_CLASS_REFERENCE}.
|
|
*/
|
|
public Class<?> getDeclaringClass();
|
|
|
|
/**
|
|
* Returns the {@link MethodType} representing the parameter types and
|
|
* the return type for the method represented by this stack frame.
|
|
*
|
|
* @implSpec
|
|
* The default implementation throws {@code UnsupportedOperationException}.
|
|
*
|
|
* @return the {@code MethodType} for this stack frame
|
|
*
|
|
* @throws UnsupportedOperationException if this {@code StackWalker}
|
|
* is not configured with {@link Option#RETAIN_CLASS_REFERENCE
|
|
* Option.RETAIN_CLASS_REFERENCE}.
|
|
*
|
|
* @since 10
|
|
*/
|
|
public default MethodType getMethodType() {
|
|
throw new UnsupportedOperationException();
|
|
}
|
|
|
|
/**
|
|
* Returns the <i>descriptor</i> of the method represented by
|
|
* this stack frame as defined by
|
|
* <cite>The Java Virtual Machine Specification</cite>.
|
|
*
|
|
* @implSpec
|
|
* The default implementation throws {@code UnsupportedOperationException}.
|
|
*
|
|
* @return the descriptor of the method represented by
|
|
* this stack frame
|
|
*
|
|
* @see MethodType#fromMethodDescriptorString(String, ClassLoader)
|
|
* @see MethodType#toMethodDescriptorString()
|
|
* @jvms 4.3.3 Method Descriptor
|
|
*
|
|
* @since 10
|
|
*/
|
|
public default String getDescriptor() {
|
|
throw new UnsupportedOperationException();
|
|
}
|
|
|
|
// Android-changed: javadoc should refer to dex bytecodes on Android.
|
|
/**
|
|
* Returns the index to the {@code insns} array of a {@code code_item}
|
|
* containing the execution point represented by this stack frame.
|
|
* The code array gives the actual bytes of Dalvik bytecode
|
|
* that implement the method.
|
|
*
|
|
* @return the index to the {@code insns} array of the {@code code_item} attribute
|
|
* containing the execution point represented by this stack frame,
|
|
* or a negative number if the method is native.
|
|
*
|
|
* @jvms 4.7.3 The {@code Code} Attribute
|
|
*/
|
|
public int getByteCodeIndex();
|
|
|
|
/**
|
|
* Returns the name of the source file containing the execution point
|
|
* represented by this stack frame. Generally, this corresponds
|
|
* to the {@code SourceFile} attribute of the relevant {@code class}
|
|
* file as defined by <cite>The Java Virtual Machine Specification</cite>.
|
|
* In some systems, the name may refer to some source code unit
|
|
* other than a file, such as an entry in a source repository.
|
|
*
|
|
* @return the name of the file containing the execution point
|
|
* represented by this stack frame, or {@code null} if
|
|
* this information is unavailable.
|
|
*
|
|
* @jvms 4.7.10 The {@code SourceFile} Attribute
|
|
*/
|
|
public String getFileName();
|
|
|
|
/**
|
|
* Returns the line number of the source line containing the execution
|
|
* point represented by this stack frame. Generally, this is
|
|
* derived from the {@code LineNumberTable} attribute of the relevant
|
|
* {@code class} file as defined by <cite>The Java Virtual Machine
|
|
* Specification</cite>.
|
|
*
|
|
* @return the line number of the source line containing the execution
|
|
* point represented by this stack frame, or a negative number if
|
|
* this information is unavailable.
|
|
*
|
|
* @jvms 4.7.12 The {@code LineNumberTable} Attribute
|
|
*/
|
|
public int getLineNumber();
|
|
|
|
/**
|
|
* Returns {@code true} if the method containing the execution point
|
|
* represented by this stack frame is a native method.
|
|
*
|
|
* @return {@code true} if the method containing the execution point
|
|
* represented by this stack frame is a native method.
|
|
*/
|
|
public boolean isNativeMethod();
|
|
|
|
/**
|
|
* Gets a {@code StackTraceElement} for this stack frame.
|
|
*
|
|
* @return {@code StackTraceElement} for this stack frame.
|
|
*/
|
|
public StackTraceElement toStackTraceElement();
|
|
}
|
|
|
|
/**
|
|
* Stack walker option to configure the {@linkplain StackFrame stack frame}
|
|
* information obtained by a {@code StackWalker}.
|
|
*
|
|
* @since 9
|
|
*/
|
|
public enum Option {
|
|
/**
|
|
* Retains {@code Class} object in {@code StackFrame}s
|
|
* walked by this {@code StackWalker}.
|
|
*
|
|
* <p> A {@code StackWalker} configured with this option will support
|
|
* {@link StackWalker#getCallerClass()} and
|
|
* {@link StackFrame#getDeclaringClass() StackFrame.getDeclaringClass()}.
|
|
*/
|
|
RETAIN_CLASS_REFERENCE,
|
|
/**
|
|
* Shows all reflection frames.
|
|
*
|
|
* <p>By default, reflection frames are hidden. A {@code StackWalker}
|
|
* configured with this {@code SHOW_REFLECT_FRAMES} option
|
|
* will show all reflection frames that
|
|
* include {@link java.lang.reflect.Method#invoke} and
|
|
* {@link java.lang.reflect.Constructor#newInstance(Object...)}
|
|
* and their reflection implementation classes.
|
|
*
|
|
* <p>The {@link #SHOW_HIDDEN_FRAMES} option can also be used to show all
|
|
* reflection frames and it will also show other hidden frames that
|
|
* are implementation-specific.
|
|
*
|
|
* @apiNote
|
|
* This option includes the stack frames representing the invocation of
|
|
* {@code Method} and {@code Constructor}. Any utility methods that
|
|
* are equivalent to calling {@code Method.invoke} or
|
|
* {@code Constructor.newInstance} such as {@code Class.newInstance}
|
|
* are not filtered or controlled by any stack walking option.
|
|
*/
|
|
SHOW_REFLECT_FRAMES,
|
|
// Android-changed: Add more details about the API usage on Android.
|
|
/**
|
|
* Shows all hidden frames.
|
|
*
|
|
* <p>A Java Virtual Machine implementation may hide implementation
|
|
* specific frames in addition to {@linkplain #SHOW_REFLECT_FRAMES
|
|
* reflection frames}. A {@code StackWalker} with this {@code SHOW_HIDDEN_FRAMES}
|
|
* option will show all hidden frames (including reflection frames).
|
|
*
|
|
* @apiNote This option has the same effect as {@link #SHOW_REFLECT_FRAMES} initially,
|
|
* until the Android Runtime supports other hidden frames.
|
|
*/
|
|
SHOW_HIDDEN_FRAMES;
|
|
}
|
|
|
|
enum ExtendedOption {
|
|
/**
|
|
* Obtain monitors, locals and operands.
|
|
*/
|
|
LOCALS_AND_OPERANDS
|
|
};
|
|
|
|
static final EnumSet<Option> DEFAULT_EMPTY_OPTION = EnumSet.noneOf(Option.class);
|
|
|
|
private static final StackWalker DEFAULT_WALKER =
|
|
new StackWalker(DEFAULT_EMPTY_OPTION);
|
|
|
|
private final Set<Option> options;
|
|
private final ExtendedOption extendedOption;
|
|
private final int estimateDepth;
|
|
final boolean retainClassRef; // cached for performance
|
|
|
|
/**
|
|
* Returns a {@code StackWalker} instance.
|
|
*
|
|
* <p> This {@code StackWalker} is configured to skip all
|
|
* {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and
|
|
* no {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
|
|
*
|
|
* @return a {@code StackWalker} configured to skip all
|
|
* {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and
|
|
* no {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
|
|
*
|
|
*/
|
|
public static StackWalker getInstance() {
|
|
// no permission check needed
|
|
return DEFAULT_WALKER;
|
|
}
|
|
|
|
/**
|
|
* Returns a {@code StackWalker} instance with the given option specifying
|
|
* the stack frame information it can access.
|
|
*
|
|
* <p>
|
|
* If a security manager is present and the given {@code option} is
|
|
* {@link Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE},
|
|
* it calls its {@link SecurityManager#checkPermission checkPermission}
|
|
* method for {@code RuntimePermission("getStackWalkerWithClassReference")}.
|
|
*
|
|
* @param option {@link Option stack walking option}
|
|
*
|
|
* @return a {@code StackWalker} configured with the given option
|
|
*
|
|
* @throws SecurityException if a security manager exists and its
|
|
* {@code checkPermission} method denies access.
|
|
*/
|
|
public static StackWalker getInstance(Option option) {
|
|
return getInstance(EnumSet.of(Objects.requireNonNull(option)));
|
|
}
|
|
|
|
/**
|
|
* Returns a {@code StackWalker} instance with the given {@code options} specifying
|
|
* the stack frame information it can access. If the given {@code options}
|
|
* is empty, this {@code StackWalker} is configured to skip all
|
|
* {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and no
|
|
* {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
|
|
*
|
|
* <p>
|
|
* If a security manager is present and the given {@code options} contains
|
|
* {@link Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE},
|
|
* it calls its {@link SecurityManager#checkPermission checkPermission}
|
|
* method for {@code RuntimePermission("getStackWalkerWithClassReference")}.
|
|
*
|
|
* @param options {@link Option stack walking option}
|
|
*
|
|
* @return a {@code StackWalker} configured with the given options
|
|
*
|
|
* @throws SecurityException if a security manager exists and its
|
|
* {@code checkPermission} method denies access.
|
|
*/
|
|
public static StackWalker getInstance(Set<Option> options) {
|
|
if (options.isEmpty()) {
|
|
return DEFAULT_WALKER;
|
|
}
|
|
|
|
EnumSet<Option> optionSet = toEnumSet(options);
|
|
checkPermission(optionSet);
|
|
return new StackWalker(optionSet);
|
|
}
|
|
|
|
/**
|
|
* Returns a {@code StackWalker} instance with the given {@code options} specifying
|
|
* the stack frame information it can access. If the given {@code options}
|
|
* is empty, this {@code StackWalker} is configured to skip all
|
|
* {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} and no
|
|
* {@linkplain Option#RETAIN_CLASS_REFERENCE class reference} is retained.
|
|
*
|
|
* <p>
|
|
* If a security manager is present and the given {@code options} contains
|
|
* {@link Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE},
|
|
* it calls its {@link SecurityManager#checkPermission checkPermission}
|
|
* method for {@code RuntimePermission("getStackWalkerWithClassReference")}.
|
|
*
|
|
* <p>
|
|
* The {@code estimateDepth} specifies the estimate number of stack frames
|
|
* this {@code StackWalker} will traverse that the {@code StackWalker} could
|
|
* use as a hint for the buffer size.
|
|
*
|
|
* @param options {@link Option stack walking options}
|
|
* @param estimateDepth Estimate number of stack frames to be traversed.
|
|
*
|
|
* @return a {@code StackWalker} configured with the given options
|
|
*
|
|
* @throws IllegalArgumentException if {@code estimateDepth <= 0}
|
|
* @throws SecurityException if a security manager exists and its
|
|
* {@code checkPermission} method denies access.
|
|
*/
|
|
public static StackWalker getInstance(Set<Option> options, int estimateDepth) {
|
|
if (estimateDepth <= 0) {
|
|
throw new IllegalArgumentException("estimateDepth must be > 0");
|
|
}
|
|
EnumSet<Option> optionSet = toEnumSet(options);
|
|
checkPermission(optionSet);
|
|
return new StackWalker(optionSet, estimateDepth);
|
|
}
|
|
|
|
// ----- private constructors ------
|
|
private StackWalker(EnumSet<Option> options) {
|
|
this(options, 0, null);
|
|
}
|
|
private StackWalker(EnumSet<Option> options, int estimateDepth) {
|
|
this(options, estimateDepth, null);
|
|
}
|
|
private StackWalker(EnumSet<Option> options, int estimateDepth, ExtendedOption extendedOption) {
|
|
this.options = options;
|
|
this.estimateDepth = estimateDepth;
|
|
this.extendedOption = extendedOption;
|
|
this.retainClassRef = hasOption(Option.RETAIN_CLASS_REFERENCE);
|
|
}
|
|
|
|
private static void checkPermission(Set<Option> options) {
|
|
Objects.requireNonNull(options);
|
|
@SuppressWarnings("removal")
|
|
SecurityManager sm = System.getSecurityManager();
|
|
if (sm != null) {
|
|
if (options.contains(Option.RETAIN_CLASS_REFERENCE)) {
|
|
sm.checkPermission(new RuntimePermission("getStackWalkerWithClassReference"));
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Returns a defensive copy
|
|
*/
|
|
private static EnumSet<Option> toEnumSet(Set<Option> options) {
|
|
Objects.requireNonNull(options);
|
|
if (options.isEmpty()) {
|
|
return DEFAULT_EMPTY_OPTION;
|
|
} else {
|
|
return EnumSet.copyOf(options);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Applies the given function to the stream of {@code StackFrame}s
|
|
* for the current thread, traversing from the top frame of the stack,
|
|
* which is the method calling this {@code walk} method.
|
|
*
|
|
* <p>The {@code StackFrame} stream will be closed when
|
|
* this method returns. When a closed {@code Stream<StackFrame>} object
|
|
* is reused, {@code IllegalStateException} will be thrown.
|
|
*
|
|
* @apiNote
|
|
* For example, to find the first 10 calling frames, first skipping those frames
|
|
* whose declaring class is in package {@code com.foo}:
|
|
* <blockquote>
|
|
* <pre>{@code
|
|
* List<StackFrame> frames = StackWalker.getInstance().walk(s ->
|
|
* s.dropWhile(f -> f.getClassName().startsWith("com.foo."))
|
|
* .limit(10)
|
|
* .collect(Collectors.toList()));
|
|
* }</pre></blockquote>
|
|
*
|
|
* <p>This method takes a {@code Function} accepting a {@code Stream<StackFrame>},
|
|
* rather than returning a {@code Stream<StackFrame>} and allowing the
|
|
* caller to directly manipulate the stream. The Java virtual machine is
|
|
* free to reorganize a thread's control stack, for example, via
|
|
* deoptimization. By taking a {@code Function} parameter, this method
|
|
* allows access to stack frames through a stable view of a thread's control
|
|
* stack.
|
|
*
|
|
* <p>Parallel execution is effectively disabled and stream pipeline
|
|
* execution will only occur on the current thread.
|
|
*
|
|
* @implNote The implementation stabilizes the stack by anchoring a frame
|
|
* specific to the stack walking and ensures that the stack walking is
|
|
* performed above the anchored frame. When the stream object is closed or
|
|
* being reused, {@code IllegalStateException} will be thrown.
|
|
*
|
|
* @param function a function that takes a stream of
|
|
* {@linkplain StackFrame stack frames} and returns a result.
|
|
* @param <T> The type of the result of applying the function to the
|
|
* stream of {@linkplain StackFrame stack frame}.
|
|
*
|
|
* @return the result of applying the function to the stream of
|
|
* {@linkplain StackFrame stack frame}.
|
|
*/
|
|
@CallerSensitive
|
|
public <T> T walk(Function<? super Stream<StackFrame>, ? extends T> function) {
|
|
// Returning a Stream<StackFrame> would be unsafe, as the stream could
|
|
// be used to access the stack frames in an uncontrolled manner. For
|
|
// example, a caller might pass a Spliterator of stack frames after one
|
|
// or more frames had been traversed. There is no robust way to detect
|
|
// whether the execution point when
|
|
// Spliterator.tryAdvance(java.util.function.Consumer<? super T>) is
|
|
// invoked is the exact same execution point where the stack frame
|
|
// traversal is expected to resume.
|
|
|
|
Objects.requireNonNull(function);
|
|
return StackStreamFactory.makeStackTraverser(this, function)
|
|
.walk();
|
|
}
|
|
|
|
/**
|
|
* Performs the given action on each element of {@code StackFrame} stream
|
|
* of the current thread, traversing from the top frame of the stack,
|
|
* which is the method calling this {@code forEach} method.
|
|
*
|
|
* <p> This method is equivalent to calling
|
|
* <blockquote>
|
|
* {@code walk(s -> { s.forEach(action); return null; });}
|
|
* </blockquote>
|
|
*
|
|
* @param action an action to be performed on each {@code StackFrame}
|
|
* of the stack of the current thread
|
|
*/
|
|
@CallerSensitive
|
|
public void forEach(Consumer<? super StackFrame> action) {
|
|
Objects.requireNonNull(action);
|
|
StackStreamFactory.makeStackTraverser(this, s -> {
|
|
s.forEach(action);
|
|
return null;
|
|
}).walk();
|
|
}
|
|
|
|
/**
|
|
* Gets the {@code Class} object of the caller who invoked the method
|
|
* that invoked {@code getCallerClass}.
|
|
*
|
|
* <p> This method filters {@linkplain Option#SHOW_REFLECT_FRAMES reflection
|
|
* frames}, {@link java.lang.invoke.MethodHandle}, and
|
|
* {@linkplain Option#SHOW_HIDDEN_FRAMES hidden frames} regardless of the
|
|
* {@link Option#SHOW_REFLECT_FRAMES SHOW_REFLECT_FRAMES}
|
|
* and {@link Option#SHOW_HIDDEN_FRAMES SHOW_HIDDEN_FRAMES} options
|
|
* this {@code StackWalker} has been configured with.
|
|
*
|
|
* <p> This method should be called when a caller frame is present. If
|
|
* it is called from the bottom most frame on the stack,
|
|
* {@code IllegalCallerException} will be thrown.
|
|
*
|
|
* <p> This method throws {@code UnsupportedOperationException}
|
|
* if this {@code StackWalker} is not configured with the
|
|
* {@link Option#RETAIN_CLASS_REFERENCE RETAIN_CLASS_REFERENCE} option.
|
|
*
|
|
* @apiNote
|
|
* For example, {@code Util::getResourceBundle} loads a resource bundle
|
|
* on behalf of the caller. It invokes {@code getCallerClass} to identify
|
|
* the class whose method called {@code Util::getResourceBundle}.
|
|
* Then, it obtains the class loader of that class, and uses
|
|
* the class loader to load the resource bundle. The caller class
|
|
* in this example is {@code MyTool}.
|
|
*
|
|
* <pre>{@code
|
|
* class Util {
|
|
* private final StackWalker walker = StackWalker.getInstance(Option.RETAIN_CLASS_REFERENCE);
|
|
* public ResourceBundle getResourceBundle(String bundleName) {
|
|
* Class<?> caller = walker.getCallerClass();
|
|
* return ResourceBundle.getBundle(bundleName, Locale.getDefault(), caller.getClassLoader());
|
|
* }
|
|
* }
|
|
*
|
|
* class MyTool {
|
|
* private final Util util = new Util();
|
|
* private void init() {
|
|
* ResourceBundle rb = util.getResourceBundle("mybundle");
|
|
* }
|
|
* }
|
|
* }</pre>
|
|
*
|
|
* An equivalent way to find the caller class using the
|
|
* {@link StackWalker#walk walk} method is as follows
|
|
* (filtering the reflection frames, {@code MethodHandle} and hidden frames
|
|
* not shown below):
|
|
* <pre>{@code
|
|
* Optional<Class<?>> caller = walker.walk(s ->
|
|
* s.map(StackFrame::getDeclaringClass)
|
|
* .skip(2)
|
|
* .findFirst());
|
|
* }</pre>
|
|
*
|
|
* When the {@code getCallerClass} method is called from a method that
|
|
* is the bottom most frame on the stack,
|
|
* for example, {@code static public void main} method launched by the
|
|
* {@code java} launcher, or a method invoked from a JNI attached thread,
|
|
* {@code IllegalCallerException} is thrown.
|
|
*
|
|
* @return {@code Class} object of the caller's caller invoking this method.
|
|
*
|
|
* @throws UnsupportedOperationException if this {@code StackWalker}
|
|
* is not configured with {@link Option#RETAIN_CLASS_REFERENCE
|
|
* Option.RETAIN_CLASS_REFERENCE}.
|
|
* @throws IllegalCallerException if there is no caller frame, i.e.
|
|
* when this {@code getCallerClass} method is called from a method
|
|
* which is the last frame on the stack.
|
|
*/
|
|
@CallerSensitive
|
|
public Class<?> getCallerClass() {
|
|
if (!retainClassRef) {
|
|
throw new UnsupportedOperationException("This stack walker " +
|
|
"does not have RETAIN_CLASS_REFERENCE access");
|
|
}
|
|
|
|
return StackStreamFactory.makeCallerFinder(this).findCaller();
|
|
}
|
|
|
|
// ---- package access ----
|
|
|
|
static StackWalker newInstance(Set<Option> options, ExtendedOption extendedOption) {
|
|
EnumSet<Option> optionSet = toEnumSet(options);
|
|
checkPermission(optionSet);
|
|
return new StackWalker(optionSet, 0, extendedOption);
|
|
}
|
|
|
|
int estimateDepth() {
|
|
return estimateDepth;
|
|
}
|
|
|
|
boolean hasOption(Option option) {
|
|
return options.contains(option);
|
|
}
|
|
|
|
boolean hasLocalsOperandsOption() {
|
|
return extendedOption == ExtendedOption.LOCALS_AND_OPERANDS;
|
|
}
|
|
}
|