public interface MethodHandleInfo
Lookup.revealDirect.
ldc instruction on a CONSTANT_MethodHandle constant.
(See the Java Virtual Machine Specification, sections 4.4.8 and 5.4.3.)
Lookup.findVirtual,
to resolve a symbolic reference into a method handle.
A symbolic reference consists of a class, name string, and type.
Lookup.unreflect
or Lookup.unreflectSpecial
to convert a Method into a method handle.
Lookup.unreflectConstructor
to convert a Constructor into a method handle.
Lookup.unreflectGetter
or Lookup.unreflectSetter
to convert a Field into a method handle.
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 kind | descriptive name | scope | member | behavior |
|---|---|---|---|---|
1 | REF_getField | class |
FT f; | (T) this.f; |
2 | REF_getStatic | class or interface |
staticFT f; | (T) C.f; |
3 | REF_putField | class |
FT f; | this.f = x; |
4 | REF_putStatic | class |
staticFT f; | C.f = arg; |
5 | REF_invokeVirtual | class |
T m(A*); | (T) this.m(arg*); |
6 | REF_invokeStatic | class or interface |
staticT 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*); |
| Modifier and Type | Field and Description |
|---|---|
static int |
REF_getField
A direct method handle reference kind,
as defined in the table above.
|
static int |
REF_getStatic
A direct method handle reference kind,
as defined in the table above.
|
static int |
REF_invokeInterface
A direct method handle reference kind,
as defined in the table above.
|
static int |
REF_invokeSpecial
A direct method handle reference kind,
as defined in the table above.
|
static int |
REF_invokeStatic
A direct method handle reference kind,
as defined in the table above.
|
static int |
REF_invokeVirtual
A direct method handle reference kind,
as defined in the table above.
|
static int |
REF_newInvokeSpecial
A direct method handle reference kind,
as defined in the table above.
|
static int |
REF_putField
A direct method handle reference kind,
as defined in the table above.
|
static int |
REF_putStatic
A direct method handle reference kind,
as defined in the table above.
|
| Modifier and Type | Method and Description |
|---|---|
Class<?> |
getDeclaringClass()
Returns the class in which the cracked method handle's underlying member was defined.
|
MethodType |
getMethodType()
Returns the nominal type of the cracked symbolic reference, expressed as a method type.
|
int |
getModifiers()
Returns the access modifiers of the underlying member.
|
String |
getName()
Returns the name of the cracked method handle's underlying member.
|
int |
getReferenceKind()
Returns the reference kind of the cracked method handle, which in turn
determines whether the method handle's underlying member was a constructor, method, or field.
|
default boolean |
isVarArgs()
Determines if the underlying member was a variable arity method or constructor.
|
static String |
referenceKindToString(int referenceKind)
Returns the descriptive name of the given reference kind,
as defined in the table above.
|
<T extends Member> |
reflectAs(Class<T> expected,
MethodHandles.Lookup lookup)
Reflects the underlying member as a method, constructor, or field object.
|
static String |
toString(int kind,
Class<?> defc,
String name,
MethodType type)
Returns a string representation for a
MethodHandleInfo,
given the four parts of its symbolic reference. |
static final int REF_getField
static final int REF_getStatic
static final int REF_putField
static final int REF_putStatic
static final int REF_invokeVirtual
static final int REF_invokeStatic
static final int REF_invokeSpecial
static final int REF_newInvokeSpecial
static final int REF_invokeInterface
int getReferenceKind()
Class<?> getDeclaringClass()
String getName()
"<init>" if the underlying member was a constructor,
else it is a simple method name or field name.MethodType getMethodType()
void.
If it is to a non-static method, the method type will not mention the this parameter.
If it is to a field and the requested access is to read the field,
the method type will have no parameters and return the field type.
If it is to a field and the requested access is to write the field,
the method type will have one parameter of the field type and return void.
Note that original direct method handle may include a leading this parameter,
or (in the case of a constructor) will replace the void return type
with the constructed class.
The nominal type does not include any this parameter,
and (in the case of a constructor) will return void.
<T extends Member> T reflectAs(Class<T> expected, MethodHandles.Lookup lookup)
getMethod, getConstructor, or getField.
Otherwise, it is reflected as if by
getDeclaredMethod, getDeclaredConstructor, or getDeclaredField.
The underlying member must be accessible to the given lookup object.T - the desired type of the result, either Member or a subtypeexpected - a class object representing the desired result type Tlookup - the lookup object that created this MethodHandleInfo, or one with equivalent access privilegesClassCastException - if the member is not of the expected typeNullPointerException - if either argument is nullIllegalArgumentException - if the underlying member is not accessible to the given lookup objectint getModifiers()
Modifier,
reflectAs(java.lang.Class<T>, java.lang.invoke.MethodHandles.Lookup)default boolean isVarArgs()
getReferenceKind() >= REF_invokeVirtual && Modifier.isTransient(getModifiers())
true if and only if the underlying member was declared with variable arity.static String referenceKindToString(int referenceKind)
referenceKind - an integer code for a kind of reference used to access a class member"getField"IllegalArgumentException - if the argument is not a valid
reference kind numberstatic String toString(int kind, Class<?> defc, String name, MethodType type)
MethodHandleInfo,
given the four parts of its symbolic reference.
This is defined to be of the form "RK C.N:MT", where RK is the
reference kind string for kind,
C is the name of defc
N is the name, and
MT is the type.
These four values may be obtained from the
reference kind,
declaring class,
member name,
and method type
of a MethodHandleInfo object.
String.format("%s %s.%s:%s", referenceKindToString(kind), defc.getName(), name, type)
kind - the reference kind part of the symbolic referencedefc - the declaring class part of the symbolic referencename - the member name part of the symbolic referencetype - the method type part of the symbolic reference"RK C.N:MT"IllegalArgumentException - if the first argument is not a valid
reference kind numberNullPointerException - if any reference argument is null Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
Copyright © 1993, 2020, Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.