Hi John,
I peeked at the implementation of HMI.asMember method:
111 + // Helper for default MethodHandleInfo.asMember.
112 + static Member reflectMember(MethodHandleInfo self)
throws ReflectiveOperationException {
113 + int mods = self.getModifiers();
114 + if (mods == -1) throw notDirectMethodHandle();
115 + byte refKind = (byte) self.getReferenceKind();
116 + Class<?> defc = self.getDeclaringClass();
117 + boolean isPublic = Modifier.isPublic(mods);
118 + if (MethodHandleNatives.refKindIsMethod(refKind)) {
119 + if (isPublic)
120 + return defc.getMethod(self.getName(),
self.getMethodType().parameterArray());
121 + else
122 + return
defc.getDeclaredMethod(self.getName(),
self.getMethodType().parameterArray());
123 + } else if
(MethodHandleNatives.refKindIsConstructor(refKind)) {
124 + if (isPublic)
125 + return
defc.getConstructor(self.getMethodType().parameterArray());
126 + else
127 + return
defc.getDeclaredConstructor(self.getMethodType().parameterArray());
128 + } else if
(MethodHandleNatives.refKindIsField(refKind)) {
129 + if (isPublic)
130 + return defc.getField(self.getName());
131 + else
132 + return defc.getDeclaredField(self.getName());
133 + } else {
134 + throw new
IllegalArgumentException("referenceKind="+refKind);
135 + }
136 + }
...
408 + public default <T extends Member> T asMember(Class<T>
expected) {
409 + Member mem = AccessController.doPrivileged(new
PrivilegedAction<Member>() {
410 + public Member run() {
411 + try {
412 + return
InfoFromMemberName.reflectMember(MethodHandleInfo.this);
413 + } catch (ReflectiveOperationException ex) {
414 + throw newInternalError(ex);
415 + }
416 + }
417 + });
418 + return expected.cast(mem);
419 }
Are special cases for public members just because the reflection API
requires different privileges for public vs. declared member access? But
InfoFromMemberName.reflectMember() is package-private and is called from
within a PrivilegedAction in MHI.asMember() which is a system class. If
MHI objects are not considered "security sensitive tokens" like MH
objects, then perhaps MHI.asMember should not wrap the call to
InfoFromMemberName.reflectMember() in a PrivilegedAction...
Regards, Peter
On 05/15/2013 07:58 AM, John Rose wrote:
> Here is an update on the method handle cracking API.
>
> Though we will probably make some small adjustments, it appears to be
> converging.
>
> http://cr.openjdk.java.net/~jrose/8008688/specdiff.02/
> http://cr.openjdk.java.net/~jrose/8008688/javadoc.02/
>
> Key points:
>
> - interface MethodHandleInfo (MHI) presents a "cracked" symbolic reference
> for the member underlying a direct method handle (DMH)
> - cracking of method handles which are not DMHs is left for the future
> - you need the original Lookup object associated with DMH creation in order
> to crack it; this prevents side-channels
>
> - there are access methods for the four components (ref kind, class, name,
> type) of the CONSTANT_MethodHandle (or equivalent information) that was used
> to create the DMH
> - there is a bridge (asMember) from MHI to the Core Reflection API (can be
> built by user but very complex)
> - there is a fast path to the modifier bits of the underlying member (for
> checking public, varargs, etc.)
> - there are two static utility methods on MHI, toString and
> getReferenceKindString
>
> - there is also an unchecked version of the cracker
> (revealDirectAsAccessibleObject), which always makes a security manager call
> and bridges directly to the Core Reflection API
>
> - Modifier.isVarArgs and Modifier.VARARGS are made public, because there was
> no standard test, and variable arity is a key MethodHandle property
>
> The implementation patch is refreshed:
>
> http://hg.openjdk.java.net/mlvm/mlvm/jdk/file/tip/meth-info-8008688.patch
>
> Changes since last E-mail:
>
> - added revealDirectAsAccessibleObject
> - revealDirectAsAccessibleObject performs the same strong SM check as
> setAccessible
> - when either revealDirect function is called on a non-DMH, you get
> NoSuchMethodException
> - refined the types and documentation of exceptions and throws
> - removed static methods from MHI, except getReferenceKindString and toString
> - moved isVarArgs to java.lang.reflect.Modifier, where it belongs
>
> Possible loose ends:
>
> - minor name changes
> - MHI.toMember needs a more precise spec, and the default method is dodgy
> - could change ReflectiveOperationExceptions to IllegalArgumentExceptions,
> since the range of possible ROEs is quite limited
>
> — John
> _______________________________________________
> mlvm-dev mailing list
> mlvm-dev@openjdk.java.net
> http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev
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