Re: [shared] trivial fix for missing serialVersionUID

Wed, 24 Oct 2007 10:02:20 -0700

Indeed the serialVersionUID is used to distinguish between two versions of the same class. And simply put, it's a performance enhancement. If serialVersionUID is not present, Java will calculate one based on the hash (I think). The thing is that needing to calculate a "hash" each time a class is serialized takes time. So providing a serialVersionUID is a lot more efficient.
The thing you have to watch out for is if there is anything that will break serial compatibility, you need to be sure to increment (or recalculate) the serialVersionUID. 

Scott

Martin Marinschek wrote:

Exactly - that's for sure. If it wasn't like that, Eclipse wouldn't
use 1 as a default version id. If it was like Dennis suggested, every
app built with Eclipse would go kaboom.

;)

regards,

Martin

On 10/24/07, Mike Kienenberger <[EMAIL PROTECTED]> wrote:

  

Yes, wouldn't that have to be the case?   Otherwise, A.jar and B.jar,
created by two independent groups, might use the same version id
without realizing it, and thus break a project depending on both of
them.


On 10/24/07, Martin Marinschek <[EMAIL PROTECTED]> wrote:

    

The stream identifier will take into account the FQCN, and the
version-identifier - so the two classes won't have the same stream
identifier, IMHO.

regards,

Martin

On 10/19/07, Dennis Byrne <[EMAIL PROTECTED]> wrote:

      

Please consider the consequences of two different classes w/ the same

        

stream

    

identifier.

Dennis Byrne

On 10/19/07, simon <[EMAIL PROTECTED]> wrote:

        

Why would that make any difference? The classes are in two different
packages....

On Fri, 2007-10-19 at 14:29 -0500, Dennis Byrne wrote:

          

(not sure if this issue has been covered yet in this thread)

Because these classes are in shared, they will be "split" into two
classes, one for core and one for tomahawk.  When they are split,

            

you

    

will have two completely classes in the JVM who have the same serial
id.  I'm not going to say "don't do it", but I do think we can agree
this is not a good idea?

Dennis Byrne

On 10/19/07, Simon Kitching <[EMAIL PROTECTED]> wrote:
        Hi All,

        I'd like to make a trivial commit to add serialVersionUID
        values to two classes in shared that don't yet have them.

            

This

    

        avoids compile warnings in IDEs that have "warn on missing
        serialVersionUID" set.

        Adding the serialVersionUID is technically the right thing

            

to

    

        do, IMO although in practice I agree it isn't terribly
        important for these particular classes.

        Any objections?

        Cheers,

        Simon

        Index:

            

/home/sk/projects/apache/myfaces/shared/core/src/main/java/org/apache/myfaces/shared/renderkit/RendererUtils.java

    

===================================================================

          

        ---

            

/home/sk/projects/apache/myfaces/shared/core/src/main/java/org/apache/myfaces/shared/renderkit/RendererUtils.java

    

(revision 586396)

          

        +++

            

/home/sk/projects/apache/myfaces/shared/core/src/main/java/org/apache/myfaces/shared/renderkit/RendererUtils.java

    

(working copy)

          

        @@ -74,6 +74,7 @@
             public static final String SELECT_ITEM_LIST_ATTR =
        RendererUtils.class.getName () + ".LIST";
             public static final String EMPTY_STRING = "";
             public static final Object NOTHING = new Serializable()

            

{

    

        +        private static final long serialVersionUID =
        -8618356560493578754L;
             };

             public static final String ACTION_FOR_LIST =
        "org.apache.myfaces.ActionForList";


        Index:

            

/home/sk/projects/apache/myfaces/shared/core/src/main/java/org/apache/myfaces/shared/util/servlet/SourceCodeServlet.java

    

===================================================================

          

        ---

            

/home/sk/projects/apache/myfaces/shared/core/src/main/java/org/apache/myfaces/shared/util/servlet/SourceCodeServlet.java

    

   (revision

        

586396)

          

        +++

            

/home/sk/projects/apache/myfaces/shared/core/src/main/java/org/apache/myfaces/shared/util/servlet/SourceCodeServlet.java

    

   (working

        

copy)

          

        @@ -25,6 +25,8 @@

        public class SourceCodeServlet extends HttpServlet
        {
        +    private static final long serialVersionUID =
        -2233965185519715475L;
        +
             public void doGet(HttpServletRequest req,
        HttpServletResponse res)
                 throws IOException, ServletException
             {




--
Dennis Byrne

            

          

--
Dennis Byrne


        

--

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