JDK 8 RFR for JDK-7185456 : (ann) Optimize Annotation handling in java/sun.reflect.* code for small number of annotationsC (original) (raw)

Joel Borggrén-Franck joel.franck at oracle.com
Wed Mar 27 14🔞03 UTC 2013

On 03/27/2013 03:00 PM, Peter Levart wrote:

On 03/27/2013 02:00 PM, Joel Borggrén-Franck wrote:

Hi Peter,

On 03/27/2013 01:31 PM, Peter Levart wrote:

I also don't know whether having LinkedHashMap instead of plain HashMap is necessary, since it is initialized with defaults from plain HashMap (which is hashCode % capacity ordered) and only some of defaults are overridden in parsing loop in general. For example, having this annotation:

@interface Ann { String one(); String two() default "2"; } and usage: @Ann(one = "1") ...toString will print: @Ann(two = "2", one = "1")

While there perhaps is no natural ordering between the sets of default elements and non-default elements you probably want an order following source as closely as possible among the non-default elements. What is the order of elements in java class file (the bytes that the parser interprets)? Is it taken from the declaration of annotation (the order of methods in annotation interface) or from the use-site of the annotation? Is this specified?

In general javac tries to keep source order on "things" when emitting to a class file. I believe this is often specified as natural order, but don't trust me on this. In this specific case I would guess element use order from the annotatio instance.

In the following small example I note that 'b' comes before 'a' in the const pool but the RuntimeInvisibleAnnotations 'a' is before 'b'. I don't think this is a coincidence.

anno-order$ cat T.java @T(a="XYZ", b="DEF") public @interface T { String b(); String a(); }

anno-order$ javap -v T.class Classfile /localhome/src/test/anno-order/T.class Last modified Mar 27, 2013; size 239 bytes MD5 checksum e1c7d8d76842d219c9853463af37830a Compiled from "T.java" public interface T extends java.lang.annotation.Annotation SourceFile: "T.java" RuntimeInvisibleAnnotations: 0: #10(#6=s#11,#4=s#12) minor version: 0 major version: 52 flags: ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT, ACC_ANNOTATION Constant pool: #1 = Class #13 // T #2 = Class #14 // java/lang/Object #3 = Class #15 // java/lang/annotation/Annotation #4 = Utf8 b #5 = Utf8 ()Ljava/lang/String; #6 = Utf8 a #7 = Utf8 SourceFile #8 = Utf8 T.java #9 = Utf8 RuntimeInvisibleAnnotations #10 = Utf8 LT; #11 = Utf8 XYZ #12 = Utf8 DEF #13 = Utf8 T #14 = Utf8 java/lang/Object #15 = Utf8 java/lang/annotation/Annotation

For more examples of order discussions see the recent discussion on enhanced-metadata-spec-discuss at openjdk.java.net on annotation ordering in reflection and javax.lang.model.

cheers /Joel

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