Hi All,

I've come across a yet another concurrency based bug in FOP, this time to
do with how we handle AFP character-sets. The problem in this scenario is
that the CharacterSetBuilders are singletons and their creation wasn't
really intended to be used in a heavily multithreaded system. As such, we
don't really have a good implementation of a thread-safe cache for caching
expensive-to-create objects.

That's the problem I'm looking to solve, and the solution? Guava. The Guava
libraries [1] (under Apache 2.0 license) have well tested, intuitive
classes that do a lot of the low-level mechanisms that we often need, and
there's really no point in reinventing the wheel. The obvious cost of
adding this library is the addition of a JAR in the class-path, as such I'm
not calling for a vote at this point, I just wanted to know what the
general consensus on this was. The Guava library is often heralded as "the
new Apache Commons" and praised for being well maintained [2][3] but I'd
suggest if anyone is sceptical of the benefits, to do some research. I
accept, however, that developers can get a religious zeal about these kind
of things, I'm not suggesting Guava is the cure to world poverty, just that
it could help handle some of the lower-level tools. Though I'd love to
spend time implementing fit-for-purpose mechanisms, these issues are
usually bugs that our clients want fixed NOW!!! And so we find ourselves
constantly saying "ok, we'll do it this way for now, but next time we'll
find a proper fix"...

This is a subject I've been wanting to bring up for a while, we've had to
implement several thread-safe caching systems (for example in the
pdf-image-plugin) but I wanted to wait for compelling reason. Though the
reason above isn't any more compelling than for the pdf-image-plugin, I
think the addition of this library would prevent some of the low-level
mistakes that we all make sometimes.

If anyone has questions, I'd be happy to explain my motivations in further
detail.

Mehdi

[1] http://code.google.com/p/guava-libraries/
[2]
http://stackoverflow.com/questions/1444437/apache-commons-vs-guava-formerly-google-collections
[3]
http://stackoverflow.com/questions/4542550/what-are-the-big-improvements-between-guava-and-apache-equivalent-libraries

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