Summary

Add methods to StackFrame to return the method signature information at runtime.

Problem

Method signature is one important part of a stack frame but is not available in JDK 9. Exposing method signature will provide the complete information of a stack frame and enable one to look up the method reflectively, if desire.

Solution

This proposes to add StackFrame::getMethodType and StackFrame::getDescriptor to return the method type of this stack frame and the method descriptor string respectively. The MethodType is only available when the stack walker has the Option.RETAIN_CLASS_REFERENCE capability, similar to getDeclaringClass; otherwise access to the method type will not be available.

Specification

/** 
 * 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();
}