public interface MethodHandleInfo

A symbolic reference obtained by cracking a direct method handle into its consitutent symbolic parts. To crack a direct method handle, call Lookup.revealDirect.

Direct Method Handles

A direct method handle represents a method, constructor, or field without any intervening argument bindings or other transformations. The method, constructor, or field referred to by a direct method handle is called its underlying member . Direct method handles may be obtained in any of these ways:

• By executing an ldc instruction on a CONSTANT_MethodHandle constant. (See the Java Virtual Machine Specification, sections 4.4.8 and 5.4.3.)
• By calling one of the Lookup Factory Methods , such as Lookup.findVirtual, to resolve a symbolic reference into a method handle. A symbolic reference consists of a class, name string, and type.
• By calling the factory method Lookup.unreflect or Lookup.unreflectSpecial to convert a Method into a method handle.
• By calling the factory method Lookup.unreflectConstructor to convert a Constructor into a method handle.
• By calling the factory method Lookup.unreflectGetter or Lookup.unreflectSetter to convert a Field into a method handle.

Restrictions on Cracking

Given a suitable Lookup object, it is possible to crack any direct method handle to recover a symbolic reference for the underlying method, constructor, or field. Cracking must be done via a Lookup object equivalent to that which created the target method handle, or which has enough access permissions to recreate an equivalent method handle.

If the underlying method is caller sensitive , the direct method handle will have been "bound" to a particular caller class, the lookup class of the lookup object used to create it. Cracking this method handle with a different lookup class will fail even if the underlying method is public (like Class.forName).

The requirement of lookup object matching provides a "fast fail" behavior for programs which may otherwise trust erroneous revelation of a method handle with symbolic information (or caller binding) from an unexpected scope. Use MethodHandles.reflectAs(java.lang.Class<T>, java.lang.invoke.MethodHandle) to override this limitation.

Reference kinds

The Lookup Factory Methods correspond to all major use cases for methods, constructors, and fields. These use cases may be distinguished using small integers as follows:

reference kinds

reference kind	descriptive name	scope	member	behavior
1	REF_getField	class	FT f;	(T) this.f;
2	REF_getStatic	class or interface	static FT f;	(T) C.f;
3	REF_putField	class	FT f;	this.f = x;
4	REF_putStatic	class	static FT f;	C.f = arg;
5	REF_invokeVirtual	class	T m(A*);	(T) this.m(arg*);
6	REF_invokeStatic	class or interface	static T m(A*);	(T) C.m(arg*);
7	REF_invokeSpecial	class or interface	T m(A*);	(T) super.m(arg*);
8	REF_newInvokeSpecial	class	C(A*);	new C(arg*);
9	REF_invokeInterface	interface	T m(A*);	(T) this.m(arg*);