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From "Ilya Okomin" <ilya.oko...@gmail.com>
Subject Re: [classlib][luni] Strange serialized form of java.util.TreeMap (re JIRA harmony-1066)
Date Mon, 07 Aug 2006 11:18:19 GMT
On 8/7/06, Oleg Khaschansky <oleg.v.khaschansky@gmail.com> wrote:
>
> Hi,
>
> Take a look at this:
> http://download.java.net/jdk6/docs/api/serialized-form.html
> Maybe this document will give you an idea of what are those inner
> classes... Of cause, in the new release serialized form may have
> changed.


Oleg, ASFAIK the main issue is that TreeMap.headMap() returns the private
implemention of SortedMap class. This SortedMap implementation serializable
on RI, but it is undocumented in the spec. Spark Shen has just provided
tests that show strange behavior of serialization and deserialization of
this SortedMap implementation on RI.
I'm not sure we can find anything usefull on the link you've provided,
because there only serialization forms for public classes are described (if
I'm not mistaken:)).

Thanks,
Ilya.

--
> Oleg
>
> On 8/7/06, Spark Shen <smallsmallorgan@gmail.com> wrote:
> > Hi:
> > This is a long post, thanks for your patient to read it through :-)
> >
> > I wrote a test case as below:
> > public void test_SubMap_Serializable() throws Exception {
> >        TreeMap<Integer, Double> map = new TreeMap<Integer, Double>();
> >        map.put(1, 2.1);
> >        map.put(2, 3.1);
> >        map.put(3, 4.5);
> >        map.put(7, 21.3);
> >        SortedMap<Integer, Double> headMap = map.headMap(3);
> >        assertTrue(headMap instanceof Serializable);
> >        assertFalse(headMap instanceof TreeMap);
> >        assertTrue(headMap instanceof SortedMap);
> > }
> > Which says the returned headMap is not a TreeMap but a serializable
> > SortedMap.
> >
> > IIRC, there are three mysterious serialized form immediately following
> > the serialized form of java.util.TreeMap. They are
> >
> > Class **java.util.TreeMap$1** extends Object implements Serializable
> >
> > Class **java.util.TreeMap$2** extends Object implements Serializable
> >
> > Class **java.util.TreeMap$3** extends Object implements Serializable
> >
> > respectively. This gives a hint that there are three inner classes of
> > TreeMap which should be serializable.
> > But what are they indeed?
> > IMHO, the returned SortedMap may
> > be one of the java.util.TreeMap$x classes. What is your opinion? (I
> > raised JIRA-1066 for this)
> >
> > The above test case suggests me to make the returned SortedMap
> > serializable. But, I have another concern:
> > SortedMap returned by TreeMap is not a public class(does not have a
> > documented Serialized form), and the serialization behavior of this
> > SortedMap is strange. See the test case below:
> > public void test_HeadMap_Serializable() throws Exception {
> >        TreeMap<Integer, Double> map = new TreeMap<Integer, Double>();
> >        map.put(1, 2.1);
> >        map.put(2, 3.1);
> >        map.put(3, 4.5);
> >        map.put(7, 21.3);
> >        SortedMap<Integer, Double> headMap = map.headMap(3);
> >        assertTrue(headMap instanceof Serializable);
> >        assertFalse(headMap instanceof TreeMap);
> >        assertTrue(headMap instanceof SortedMap);
> >
> >         // Write the SortedMap out and read it back.
> >         ByteArrayOutputStream bos = new ByteArrayOutputStream();
> >        ObjectOutputStream oos = new ObjectOutputStream(bos);
> >        oos.writeObject(headMap);
> >        oos.close();
> >
> >        ByteArrayInputStream bis = new
> > ByteArrayInputStream(bos.toByteArray());
> >        ObjectInputStream ois = new ObjectInputStream(bis);
> >        Object outputObject = (Object) ois.readObject();
> >
> >        *assertNull(((SortedMap)outputObject).entrySet());
> >
> >        assertNotNull(((SortedMap)outputObject).keySet());
> >
> >        assertNotNull(((SortedMap)outputObject).values());
> >
> > *        *// assertEquals(outputObject, headMap);*
> > }
> >
> > The commented out assertion will throw out a NullPointerException, and
> > the entrySet of the SortedMap is Null while keySet and values are not.
> > This is strange. Do we need to follow RI to make the returned SortedMap
> > serializable like this?
> >
> > Best regards
> >
> > --
> > Spark Shen
> > China Software Development Lab, IBM
> >
> >
> >
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> >
> >
>
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>


-- 
--
Ilya Okomin
Intel Middleware Products Division

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