Code Review for JEP 259: Stack-Walking API (original) (raw)

Mandy Chung mandy.chung at oracle.com
Tue Nov 17 23:56:05 UTC 2015

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Thanks Peter.

- threre's no ResourceBundle.getBundle(String, ClassLoader) method. - Util -> ResourceBundleUtil (or ResourceBundleUtil -> Util)

Fixed.

: - Stream.findFirst() returns Optional, not E.

Fixed.

I updated javadoc for getCallerClass per our discussion.

/**

• Gets the {@code Class} object of the caller invoking the method
• that calls this {@code getCallerClass} method.

• Reflection frames, {@link java.lang.invoke.MethodHandle} and

• hidden frames are filtered regardless of the
• {@link Option#SHOW_REFLECT_FRAMES SHOW_REFLECT_FRAMES}
• and {@link Option#SHOW_HIDDEN_FRAMES SHOW_HIDDEN_FRAMES} options
• if this {@code StackWalker} has been configured.

• This method throws {@code UnsupportedOperationException} if

• this {@code StackWalker} is not configured with
• {@link Option#RETAIN_CLASS_REFERENCE RETAIN_CLASS_REFERENCE} option
• or this method is called from the last frame on the stack.
• @apiNote
• For example, {@code Util::getResourceBundle} loads a resource bundle
• on behalf of the caller. It calls this {@code getCallerClass} method
• to find the method calling {@code Util::getResourceBundle} and use the caller's
• class loader to load the resource bundle. The caller class in this example
• is the {@code MyTool} class.

• {@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");

•     }

• }

• }
• 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):

• {@code

• Optional<Class<?>> caller = walker.walk(s ->

•     s.map(StackFrame::getDeclaringClass)

•      .skip(2)

•      .findFirst());

• }
• When the {@code getCallerClass} method is called from a method that
• is the last 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 UnsupportedOperationException} 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 UnsupportedOperationException 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.

*/

Mandy

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