Wednesday Jun 01, 2011

JavaOne 2007

Come to our BOF sessions at JavaOne and hear more about the Java programming language and the Java technology tools (including javac).

BOF-2899: Java Programming Language Features in JDK Release 7
Track: Java SE
Room: Gateway 102/103
Date: 08-MAY-07
Start Time: 22:00
BOF-2898: Java Programming Language, Java Compiler, and Related Tools and API
Track: Java SE; Open Source
Room: Room 105
Date: 09-MAY-07
Start Time: 19:55

One more interview

Since you are reading my blog you may also find Meet Peter von der Ahé, Tech Lead for javac at Sun Microsystems interesting. For now, the interview is on the front page.

JSR 199 Interview

Frank Sommers of Artima asked me a few questions about the Java Compiler API (JSR 199) and the Kitchen Sink Language: The Java Compiler API: A Conversation with Peter von der Ahé.

Tip: How to get nice URLs on your blog

URLs should be nice and easy to read and remember (see URL as UI). Here is a tip for doing that in Apache Roller, the blog software used on blogs.sun.com: before you save your blog entry the first time, provide a short title of the entry that will look good in the URL. Then save the first draft and Roller will pick the title for the permalink. Now you can change the title to what ever you feel is right but the nice URL will remain.

Coding Conventions and Attribution

Open sourcing of javac (and the JDK) is an opportunity to revisit our current practices and think about what is missing, what needs to be updated, and what should stay the same. One issue is how to attribute source code with @author tags and there are different policies in use in the open source community.

The position of the Apache Software Foundation (ASF) was explained by the then president of the ASF. To summarize, the ASF recommends against putting @author tags in source code for these reasons:

  • Attributions in source files are not up to date.
  • Software is a team effort.
  • ASF sells the code base as an ASF brand.
  • Shield against law-suits.

However, those concerns are not that convincing to me and are far out-weighed by the need for programmers to take responsibility for the code they write. In Pragmatic Programmer: from journeyman to master, Hunt and Thomas recommend that programmers sign their work, tip 70. They further say:

We want to see pride of ownership. I wrote this, and I stand behind my work.

The former president of ASF has a good point that @author tags should be kept up to date. I agree and think the solution is to ensure they are kept up to date with a clear policy and code reviews. For example, if you create a new class or make significant changes to its API add an @author tag. If you make a minor change make sure your name is in the project's contributor file but do not add an @author tag.

Another point made by the ASF is that software is created by a team and the strength of the brand. I agree that software is created as a team and I think that all the team members deserves to be mentioned in a file that lists all contributors. Such a file could be part of the source bundle and also be prominently linked from the website. I don't think the sense of team effort is harmed by adding @author tags to source files and I don't see how it harms the brand, after all, the copyright statements remain and prominently identify the organization.

I am not a lawyer and this is not legal advice: it is plausible that there are people in other countries that should be careful about putting their names in source files because they can be sued. However, I do not see how this affects people that does not live in those countries.

I have long followed the Emacs lisp library header conventions as described in the GNU Emacs Lisp Reference Manual. As a practical matter, I think these can be directly applied to Java source code. When the Emacs lisp convention talks about file header, I think top-level class and package comment. In other words, only package and top-level class comments should contain @author tags.

It is possible to argue that we have a unique opportunity to go and clean up our sources right now before they are released to the public. However, I'm not convinced that this opportunity has not already passed. Some parts of the JDK were open sourced even before javac and HotSpot was opened in November and the public API has been part of the JDK (src.zip) for many releases. Similarly, all the sources of the JDK have been available for download under JRL since late 2004. There are people that are very sensitive to having their @author tags removed, for example, consider how the developer exa felt after he handed over a project and discovered that the new maintainers had removed his name from the source code.

Although we have not consistently used @author tags in the JDK, or even javac, I think we should keep the ones we have already and develop a consistent policy (for example inspired by the Emacs lisp conventions). It may be a good idea to hide email addresses by obfuscating existing @author tags if they contain email addresses.

Thanks to Jonathan Gibbons, Joe Darcy, and Alex Buckley for their suggestions on this text.
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