Hi,
(ouch - more than five lines once again)
We have now three script engines in microsling, and some ideas
floating around for more (SLING-90).
While I find it good to let people experiment with their favorite
scripting language (especially with the "playground" bias of
microsling), I think we need to focus a small number of languages for
our examples, and keep our microsling distribution size slow. I'd keep
only javascript / ESP in the core, and make all other engines plugins.
Script engines as plugins will be easy to do in Sling OSGi, but we
need some lightweight mechanism for microsling. The same engine jars
should be usable in both microsling and sling.
My requirements for microsling would be that any script engine jar
file found in the microsling servlet classpath is activated at
startup, including discovery of the file extensions supported by the
engine.
- o -
Here are some options, I have not used any of them before so comments
are welcome.
1) Use BSF, the Bean Scripting Framework
See http://jakarta.apache.org/bsf/, that's well-known and stable.
Not sure if and how BSF would help us make script engine plugins.
2) Use the JDK 1.6 scripting framework
http://java.sun.com/javase/6/docs/technotes/guides/scripting/programmer_guide/index.html
And that might work for JDK 1.5 as well:
http://www.oreillynet.com/onjava/blog/2007/09/scripting_api_for_everyone.html
3) Keep our existing interfaces an use the jar service provider mechanism
Jackrabbit uses that for query syntax plugins, a plugin jar needs a
text file like this one:
https://svn.apache.org/repos/asf/jackrabbit/trunk/jackrabbit-core/src/main/resources/META-INF/services/org.apache.jackrabbit.core.query.QueryTreeBuilder
which allows this class to discover the query engines:
https://svn.apache.org/repos/asf/jackrabbit/trunk/jackrabbit-core/src/main/java/org/apache/jackrabbit/core/query/QueryTreeBuilderRegistry.java
The spec is here:
http://java.sun.com/j2se/1.4.2/docs/guide/jar/jar.html#Service%20Provider
Surprisingly, it seems like javax.imageio.spi.ServiceRegistry is the
only public JDK class that implements this lookup method.
- o -
WDYT, do we agree on keeping just javascript/ESP in the core, yet
support script engine plugins in microsling?
Which plugin mechanism do you suggest?
-Bertrand
