[jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-2775) package-info.java should be optional:"convention over configuration"

[Norman Richards (JIRA)]

    [ http://jira.jboss.com/jira/browse/JBSEAM-2775?page=comments#action_12409263 ] 
            
Norman Richards commented on JBSEAM-2775:
-----------------------------------------

Ok, I've integrated something based on this.  I spent a good amount of time researching how other systems handle namespace to package mapping and thinking about how we can do something that is reasonable but not confusing.  What I checked in allows two kinds of mappings.  

The first, and what I think should be the java:packageName URIs.  I found a couple precedents for using URIs of this form, so I'm quite comfortable with that one.  It's about as clear and as terse as can be.   

I've also decided to include the http: URL mappings, but I'm not really happy with it.  It's not as clear what is going on and I really don't think it's very likely to be a meaningful URL.  However, since I'm sure some people will just feel better with a http URL, I guess it's ok.  I'd really like to discourage people from using this form.   I didn't allow in arbitrary non-HTTP schemes.  If there's a reason to allow them, we can add it back in.  However, if the user is inventing an arbitrary URL for their namespaces, why not just use the java URI?

The third consideration was of using a seam: URI.  What we proposed here would have been identical to the java: URI, so I'm not including it now.  I think there is a LOT of merit in creating new seam URIs that look like seam:core, seam:framework, etc...  For example:

<components xmlns="seam:components"> 
      <init xmlns="seam:core" debug="true"  />
      ...
</components>

or 

<components xmlns="seam:components" xmlns:core="seam:core> 
      <core:init debug="true"  />
      ...
</components>


The only problem is that the change would have a big effect on users, and it would be difficult to support the http namespaces for easier migration.  Each XSD is defined for a single namespace, and so we'd be forcing everyone to do a lot more than just bump references like components-2.0.xsd to components-2.1.xsd.  It would clean up the XML considerably though, so it's definitely worth considering.


Back to the specific changes here.  Let me know if what is checked in meets your needs.  I really tried to trim it back because the use case isn't mapping existing URLs to java package names.  The goal is to allow the user to construct specific new URLs that seam can understand easily.



> package-info.java should be optional:"convention over configuration"
> --------------------------------------------------------------------
>
>                 Key: JBSEAM-2775
>                 URL: http://jira.jboss.com/jira/browse/JBSEAM-2775
>             Project: Seam
>          Issue Type: Feature Request
>            Reporter: Eric Jung
>         Assigned To: Norman Richards
>             Fix For: 2.1.0.BETA1
>
>         Attachments: JBSEAM-2775-v3.diff, JBSEAM-2775.diff, JBSEAM-2775.diff
>
>
> Currently, package-info.java is required when referring to custom Seam components in components.xml. However, to further align Seam with the "convention over configuration" philosophy, this file can be optional by making some assumptions:
> 1. In the absence of package-info.java , the XML namespace in components.xml for custom components has a well-defined mapping to a Java package
> 2. This mapping can be defined as:
>   a. The XML namespace must be parsable by java.net.URI otherwise automatic mapping is aborted
>   a. Protocol (scheme), the www/ subdomain, port, query parameters, anchors (references), and userInfo are ignored, if present.
>   b. The top-level domain becomes the root Java package
>   c. Subdomains become Java packages under the root package, applied in right-to-left order as specified in the URI.
>   d. The path, as returned by URI.getPath(), is mapped to further Java packages such that each path element becomes another Java package appended in left-to-right order
> Examples:
> http://www.company.com/department/product ==> com.company.department.product
> https://company.com/department/product ==> com.company.department.product
> ftp://www.company.org/department/product ==> org.company.department.product
> abc://company.org/department/product ==> org.company.department.product
> company.net/foo/bar/baz ==> net.company.foo.bar.baz
> JIRA isn't displaying my last example correctly. See http://pastebin.mozilla.org/375878 for the last example.

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