Convert VarHandle to java.lang.reflect.Field

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Is there any way to convert from a VarHandle to a java.lang.reflect.Field? With a (getter/setter) MethodHandle, one can use MethodHandles.reflectAs(Field.class, handle) to go from MethodHandle to Field or lookup.unreflect{Getter|Setter}(field) to go from Field to MethodHandle. Similarly, one can use lookup.unreflectVarHandle(field) to go from Field to VarHandle, but there doesn't seem to be any equivalent way to go from VarHandle to Field.

java-9 reflection java
1 Answers

Such a function does indeed seem to be missing.

But starting with JDK 12, you can emulate it via the constant API:

Optional<Field> o = varHandle.describeConstable().map(d -> {
    String mName = d.bootstrapMethod().methodName();
    if(mName.equals("staticFieldVarHandle") || mName.equals("fieldVarHandle")) try {
        return ((Class<?>)((ClassDesc)d.bootstrapArgsList().get(0))
            .resolveConstantDesc(MethodHandles.lookup()))
            .getDeclaredField(d.constantName());
    } catch (ReflectiveOperationException ex) {}
    return null;
});

This provides the Field when the VarHandle is describing an accessible field.

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