Erik Eide
Posts: 2
Nickname: eee
Registered: Oct, 2002
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Re: Java Product Versioning
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Posted: Oct 1, 2002 5:49 AM
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> The article mentions:
>
> The java.lang.Package class provides a method
> called isCompatibleWith(String version),
> allowing the specification version of a component to
> be checked programmatically. Why is that useful? It
> allows a system's dependent parts to verify that a
> new or upgraded component conforms to the
> specification or contract that it expects it to.
>
> This surprised me, so I looked up the JavaDoc. I
> believe I misinterpreted the author when he said
> "verify that a component conforms to the spec" to
> mean a component can decide to conform to its spec or
> not, which is not the point of that method. The
> method just compares version numbers of the package
> it represents and a passed version number that is
> needed by the caller. If the version number of the
> package is greater than or equal to the passed
> version number, isCompatible returns true. So
> the inherent assumption is that every subsequent
> version of every package is binary (including
> semantics) compatible with previous versions.
Hi Bill
There was a typo on my behalf that slipped through. The intended text was "It allows a system's dependent parts to verify that a new or upgraded component conforms to the specification or contract that they expect it to."
Essentially, all I was trying to say was that we can programmatically check what version of a specification a component claims to implement. Perhaps I should of stated explicitly that this is not a check of binary compatibility of a package, such as defined in the JLS.
Unlike the specification-version attribute which is constrained to a decimal numeric type, the implementation-version attribute can contain any free-form text you wish - making it difficult to do a similar comparison.
Maybe Sun should of considered naming their method isCompatibleWithSpecification(String ver) to avoid the ambiguity of which version is being compared.
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