public static StackWalker getInstance()
StackWalker configured to skip all hidden frames and no class reference is retained.
public static StackWalker getInstance(StackWalker.Option option)
Returns a
StackWalker
instance with the given option specifying the stack frame information it can access.
If a security manager is present and the given option is Option.RETAIN_CLASS_REFERENCE, it calls its checkPermission method for RuntimePermission("getStackWalkerWithClassReference").
option - stack walking option
StackWalker configured with the given option
SecurityException - if a security manager exists and its checkPermission method denies access.
public static StackWalker getInstance(Set<StackWalker.Option> options)
Returns a
StackWalker
instance with the given
options
specifying the stack frame information it can access. If the given
options
is empty, this
StackWalker
is configured to skip all
hidden framesand no
class referenceis retained.
If a security manager is present and the given options contains Option.RETAIN_CLASS_REFERENCE, it calls its checkPermission method for RuntimePermission("getStackWalkerWithClassReference").
options - stack walking option
StackWalker configured with the given options
SecurityException - if a security manager exists and its checkPermission method denies access.
public static StackWalker getInstance(Set<StackWalker.Option> options, int estimateDepth)
Returns a
StackWalker
instance with the given
options
specifying the stack frame information it can access. If the given
options
is empty, this
StackWalker
is configured to skip all
hidden framesand no
class referenceis retained.
If a security manager is present and the given options contains Option.RETAIN_CLASS_REFERENCE, it calls its checkPermission method for RuntimePermission("getStackWalkerWithClassReference").
The estimateDepth specifies the estimate number of stack frames this StackWalker will traverse that the StackWalker could use as a hint for the buffer size.
options - stack walking options
estimateDepth - Estimate number of stack frames to be traversed.
StackWalker configured with the given options
IllegalArgumentException - if estimateDepth <= 0
SecurityException - if a security manager exists and its checkPermission method denies access.
public <T> T walk(Function<? super Stream<StackWalker.StackFrame>,? extends T> function)
Applies the given function to the stream of
StackFrame
s for the current thread, traversing from the top frame of the stack, which is the method calling this
walk
method.
The StackFrame stream will be closed when this method returns. When a closed Stream<StackFrame> object is reused, IllegalStateException will be thrown.
com.foo:
List<StackFrame> frames = StackWalker.getInstance().walk(s -> s.dropWhile(f -> f.getClassName().startsWith("com.foo.")) .limit(10) .collect(Collectors.toList()));
This method takes a Function accepting a Stream<StackFrame>, rather than returning a 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 Function parameter, this method allows access to stack frames through a stable view of a thread's control stack.
Parallel execution is effectively disabled and stream pipeline execution will only occur on the current thread.
IllegalStateException will be thrown.
T - The type of the result of applying the function to the stream of stack frame.
function - a function that takes a stream of stack frames and returns a result.
public void forEach(Consumer<? super StackWalker.StackFrame> action)
Performs the given action on each element of
StackFrame
stream of the current thread, traversing from the top frame of the stack, which is the method calling this
forEach
method.
This method is equivalent to calling
walk(s -> { s.forEach(action); return null; });
action - an action to be performed on each StackFrame of the stack of the current thread
public Class<?> getCallerClass()
Gets the
Class
object of the caller who invoked the method that invoked
getCallerClass
.
This method filters reflection frames, MethodHandle, and hidden frames regardless of the SHOW_REFLECT_FRAMES and SHOW_HIDDEN_FRAMES options this StackWalker has been configured with.
This method should be called when a caller frame is present. If it is called from the bottom most frame on the stack, IllegalCallerException will be thrown.
This method throws UnsupportedOperationException if this StackWalker is not configured with the RETAIN_CLASS_REFERENCE option.
Util::getResourceBundle loads a resource bundle on behalf of the caller. It invokes getCallerClass to identify the class whose method called 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 MyTool.
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");
}
}
walk method is as follows (filtering the reflection frames, MethodHandle and hidden frames not shown below):
Optional<Class<?>> caller = walker.walk(s ->
s.map(StackFrame::getDeclaringClass)
.skip(2)
.findFirst());
getCallerClass method is called from a method that is the bottom most frame on the stack, for example, static public void main method launched by the java launcher, or a method invoked from a JNI attached thread, IllegalCallerException is thrown.
Class object of the caller's caller invoking this method.
UnsupportedOperationException - if this StackWalker is not configured with Option.RETAIN_CLASS_REFERENCE.
IllegalCallerException - if there is no caller frame, i.e. when this getCallerClass method is called from a method which is the last frame on the stack.
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