RFR - 8132734: java.util.jar.* changes to support multi-release jar files

[Xueming Shen]

On 02/01/2016 09:58 AM, Steve Drach wrote:
>> On Jan 30, 2016, at 12:00 AM, Alan Bateman<Alan.Bateman at oracle.com>  wrote:
>>
>>
>> On 29/01/2016 17:39, Paul Sandoz wrote:
>>> :
>>> Alan’s point is that traversing using entries()/stream() always returns the versioned entries (if any) rather than all entries, thus in a sense filters.
>>>
>>> My assumption was the traversal should by default be consistent with a calls to getEntry, thus:
>>>
>>>   jarFile.stream().forEach(e ->  {
>>>      JarEntry je = jarFile.getJarEntry(e.getName());
>>>      assert e.equals(je);
>>>   });
>>>
>>> There might need to be another stream method that returns all entries.
>>>
>> Right, I'm mostly just wondering if entries()/streams() should override the entries in the stream with versioned entries and filter out the META-INF/versions/ tree.
> I don’t think so.  That kind of behavior might be difficult to understand.  Returning all the entries provides some flexibility.  One can write code like this:
>
> jarfile.stream().map(JarEntry::getName).filter(s ->  !s.startsWith(“META-INF”)).map(JarFile::getJarEntry).etc
>
> to get the versioned results for any version you specify when constructing the JarFile.

The current specification treats those class files under meta-inf/releases like
kind of "metadata" of those base entries. Ideally those files should not even
be individual "files", but part of their corresponding entries. The consumer of
the MR-Jar should not need to be aware of these version-ed entries at all to use
this MR-jar file to load classes/resources. From this point of view, these entries
probably should be "invisible" from entries()/stream(), when the jar file is opened
with "version-enabled". And all returned entries should have all their "data"
(size, csize, timestamps, crc ...) pointed to the corresponding version-ed entries,
withe the only exception is the "name".

On the other hand it might be desired to keep JarFile.entries()/stream() asis to
match their "zip file" perspective, to return "all" raw entries. Then it might also
be desired to have an alternative "versioned streamVersion()" ...

something like

     public Stream<JarEntry> stream(Release r); ?

-sherman




>> If I've gone to trouble of specifying the a Release then it seems the right thing to do. On the other hand, it comes at a cost and there will be use-cases like "get the names of all entries" that would be more efficient to just build on the current entries()/stream(). I'm loath to suggest this might need a new method but it might be one of the options to consider here. Minimally there is a javadoc to specify on how these methods behave when the JAR is multi-release and opened by specifying a release.
> How’s this?
>
> diff -r 68867430065b src/java.base/share/classes/java/util/jar/JarFile.java
> --- a/src/java.base/share/classes/java/util/jar/JarFile.java	Fri Jan 29 12:34:44 2016 -0800
> +++ b/src/java.base/share/classes/java/util/jar/JarFile.java	Mon Feb 01 09:48:05 2016 -0800
> @@ -576,9 +576,11 @@
>       }
>
>       /**
> -     * Returns an enumeration of the jar file entries.
> +     * Returns an enumeration of all the jar file entries.  Constructing this
> +     * JarFile with the {@link JarFile#JarFile(File, boolean, int, Release)}
> +     * constructor does not modify the behavior of this method.
>        *
> -     * @return an enumeration of the jar file entries
> +     * @return an enumeration of the all jar file entries
>        * @throws IllegalStateException
>        *         may be thrown if the jar file has been closed
>        */
> @@ -587,11 +589,13 @@
>       }
>
>       /**
> -     * Returns an ordered {@code Stream} over the jar file entries.
> +     * Returns an ordered {@code Stream} over all the jar file entries.
>        * Entries appear in the {@code Stream} in the order they appear in
> -     * the central directory of the jar file.
> +     * the central directory of the jar file.  Constructing this
> +     * JarFile with the {@link JarFile#JarFile(File, boolean, int, Release)}
> +     * constructor does not modify the behavior of this method.
>        *
> -     * @return an ordered {@code Stream} of entries in this jar file
> +     * @return an ordered {@code Stream} of all entries in this jar file
>        * @throws IllegalStateException if the jar file has been closed
>        * @since 1.8
>        */
>