The Spring Experience 2006 (2)
Posted by emcmanus on December 18, 2006 at 6:54 AM PST
I'm writing this in what I used to think was the world's
nastiest airport,
where I have a five-hour stopover. I'm somewhat revising my
opinion of the airport because I discovered a "Quiet Seating Area"
with real seats and real quiet. A bit like a business-class
lounge but for the plebs. So I'm sitting there typing this, with
my laptop on a table and the charger plugged in and
everything.
As I mentioned
time, I was at
Experience 2006 in Hollywood, Florida where I was speaking
about JMX stuff.
I had been surprised at how close the
the sea.
loi littorale forbids construction within a certain
distance of the sea, unless you are a member of the Saudi royal
family that the French state
want to displease. The idea is of course avoid the sort of
concrete nastiness to be seen in certain neighbouring
countries.
Anyway, some local friends set me straight. When the hotel was
built, the sea was further away! That doesn't happen much with
the dull old Mediterranean, but over there in hurricaneland it's a
different story. A constant battle with a shifting shoreline, in
fact.
But back to your regular scheduled geekery. Here are some of
the talks I attended.
Rapid Web App Development (Rob Harrop)
This was mostly about
Flow, so
I'll leave detailed comments to the Spring experts. I came away
with a few items of general interest:
-
Good tools are essential. Rob recommended having a good
IDE (IDEA, Eclipse WTP, NetBeans). He was surely preaching to
the converted here, but maybe there were one or two diehard
Emacs users in the audience.[I like Emacs a lot, and in fact I'm typing this using it.
But I wouldn't think of using it for serious Java
programming. There have been
producing IDEs in Emacs, but even I am not mad enough to use
them.]Rob also recommended the
server, at least for development. It starts in about two
seconds and has reliable hot deploy, apparently unlike its
rivals.Finally, Rob recommended Maven, notably because of its good
integration with Jetty. -
For serious work, you need to be able to attach to your
app server with a debugger. It might take a bit of
investigation to figure out how to do this, but it is a
worthwhile investment.I use NetBeans and Glassfish, and this is trivially easy.
Right-click on the app server in the Runtime tab and select
"Start in debug mode". Then, with your web app as your main
project, do "debug main project" (F5). NetBeans deploys the
app, launches it in your browser, and attaches the
debugger. -
Rob demonstrated the use of
for parts of the web app that may change often, such as the
formatting within a page. Spring can be set up so that it
continually polls the file containing the Ruby script for
changes and reloads the script if it finds any. The result is
that you can change the script and immediately see the result in
your browser without any redeploy step. Requests that were in
progress before the change continue with the old version, and
new requests use the new. Nifty.
Spring and dynamic languages (Rod Johnson, Guillaume LaForge)
Rod presented the general Spring support for dynamic languages,
such as Groovy,
Guillaume, who is the current holder of the Groovy torch, talked
about that language in particular. Script languages lend
themselves well to interactive demos, with the presenter typing
in some stuff and showing what it does. Several speakers showed
this in fact, with varying degrees of success. Guillaume's demo
went off well, except when he was smitten by the demo gods. His
computer went spontaneously into hibernation in the middle,
which caused Guillaume to emit a bad word.
I'm not sure what to think of Groovy, myself. On the plus
side, it is very similar to Java, so easy to learn and read, and
it has some powerful features. On the minus side, it smells a bit
like Perl, with these individually-nifty features slapped together
without a coherent philosophy.
JRuby (Rob Harrop)
There was some overlap with the Groovy talk here. Rob walked
through some examples of Ruby programming, stressing the
interactivity and the access to the Java platform classes. One
thing I picked up on is that Ruby (and Groovy) can make the JMX
API's
Types much more palatable. You can set things up so that
instead of accessing a field in a
CompositeData using
cd.get("maxTime") you can use
cd.maxTime. In fact Open Types are an excellent
fit for dynamic languages and I think we should revisit the
JavaScript library in the
plugin for JConsole to take that into account.
Code organization for large systems (Jürgen Höller)
I went to this talk because I work on a large system (the JDK)
and thought it would be interesting to see how others approach the
problems that arise. However, I was a bit disappointed, because
the talk was actually about one very specific problem, namely
inter-module dependencies. Furthermore Jürgen's
presentation was based on an assumption that I don't agree with,
that modules in this case correspond to Java packages. The key
message was that there should never be cyclic dependencies between
packages. For example, java.lang and java.util have a cyclic
dependency because java.lang.System.getProperties() returns
java.util.Properties, and all the classes in java.util depend on
java.lang, if only because of their common Object superclass.
An enormous amount of effort has been spent on Spring to ensure
that there are no cyclic dependencies between packages, and Jürgen
explained some of the details. But I don't think it is right to
forbid interdepencies between closely-related packages. Minimize
them, sure, but forbid them?
The problem is that the Java language doesn't currently have
any higher-level way to organize code. What we really want to
avoid is interdepencies between modules, where a module can be
made up of several packages. But there is no way in the Java
language to represent this explicitly. (There will be; see
294.) To my mind that means you need an extra-linguistic
representation, for example a file listing the packages in a
module, or the de facto grouping into jars. Then you can check
that there are no cycles. Forcing yourself never to have cycles
between packages seems like much more work than it's worth.
Glassbox - Open Source Automated Application Troubleshooting
(Ron Bodkin)
There was a bit of a screw-up for this talk, which was printed
in the conference agenda with a different subject. As a result,
there were very few people present. This is a great pity
because Glassbox is an
excellent piece of work. I had already demonstrated it briefly
in my talk and encouraged people to come to this one, but to
little avail.
I wrote about Glassbox here
but as a reminder it basically does two things:
- It uses
weaving to introduce performance probes into web apps. This
allows it to accumulate timing statistics for various things
of interest, such as servlet requests or database requests.
The statistics are available through the JMX API. - It includes its own web app that analyses these statistics
and signals possible performance problems, such as excessive
lock contention or slow database operations. In each case it
explains its reasoning. A plug-in API allows you to add your
own analysis logic.
Glassbox also supports clustered monitoring, meaning you can
see the analyses on several VMs from the same web app, including
remote VMs.
Trends and the Future of Enterprise Java (Floyd Marinescu)
Floyd fired over 90 minutes of rapid and continuous speech at
his audience in the last session slot of the conference. I left
bewildered but informed. It was also the second time in less than
24 hours that I heard a Canadian say that what defines Canadians
is that they are not American. So it must be true.
The technology trends he identified were these (quoting the
slides, with [comments]):
- Foundations of tomorrow's application design
- AOP, Dependency Injection, Annotations
- Death to components - the object fights back
- OSGi redefining the notion of an appserver
- Scripting languages
- The Resurgence of the Java Platform [as constrasted with the
Java Language] - Ruby on Rails & integrated platforms [also
Grails] - AJAX & Rich Clients [also
Flash/Flex] - Web Serviecs and SOA [put on your X-Ray skepticals]
- Java Content Repositories [JSR 170]
- The falling value proposition for EJB - can it come back?
Many of these are self-explanatory, but a few merit some
further words.
Death to components - the object fights back. As I
understand this the idea was that J2EE was not really Object
Oriented. There was an unreasonable focus on remoting of
application objects which led to twisted designs. With the switch
to POJO-based frameworks (including EJB3) and better
Object-Relation Mapping (again including EJB3), this changes.
Well, I'm not really a J2EE expert so I might be misrepresenting
the position here.
Domain Driven Design wasn't in Floyd's summary but he
spent some time talking about it anyway. It was a strong theme
at the conference with an entire track devoted to it, but I
admit I had other interests so I put off learning about it for
another day. I did notice that Domain-Specific Languages
were mentioned frequently. Especially in conjunction with Ruby
and Groovy which make it possible to construct DSLs that domain
experts can read directly even if they are not programmers. In
the spirit of objectivity, Floyd also
Buko Obele's skeptical position regarding DSLs.
Regarding OSGi, it's
clear that there was great interest at the conference in this.
The talk on the subject by Adrian Colyer was very well attended
and from what I heard extremely interesting. (Unfortunately it
would have been technically rather difficult for me to attend
since my own talk was at the same time.) Floyd felt that OSGi
will lead to increased componentisation of the Java EE platform,
so you could configure just those parts of the platform that you
need, or deploy a bundle that contains not just your web app but
the Tomcat server and configuration that supports it. I'm not
completely sure that I'm representing his position correctly or
that I agree with if so.
In the second part of the talk (I said it was long), Floyd
talked about "Business/Political Trends", namely:
- Dilution of influence of Sun and the JCP
- Emerging Economies and Open Source
- Apache Harmony [huh? didn't OpenJDK kill that?]
- Java to be open sourced - success factors
- Open Source Business Models
- Areas for commercial models?
- J2EE is already the plumbing of the future?
On Dilution of influence of Sun and the JCP, Floyd
wandered off a bit into hyperspace and ended up not even agreeing
with himself. But I think it is legitimate to note that there is
a lot of de facto standardization going on through open source
projects independently of the JCP. We were at a Spring conference
after all. The only question is whether the word "standard" is
completely appropriate in cases like this where there will in all
likelihood only ever be one implementation.
Concerning Emerging Economies and Open Source, Floyd's
most interesting point was that countries like Brazil want pure
open-source platforms to protect themselves against the effects of
possible future US trade sanctions. I don't know what to think of
that position (whether it's true, and whether it's reasonable if
it is true).
Concerning Apache Harmony and Open Source Java, the
printed slides I am working from are seriously out of date and I
admit I wasn't paying attention during this bit to see if the
slides Floyd was presenting from were less so. Sun has
announced the licensing terms, one of the two "success factors"
covered. It's true that the full governance model has yet to be
decided.
This slide was sufficiently striking to quote in full:
Harmony's only purpose was to slowly chip away Sun's resolve and
force them to eventually open source Java, under constant threat
that IBM would open source it's own Java.
Whether the meaning of the text is more accurate than its
grammar is up to you to decide. (Oh all right, I don't really
think that the two split infinitives are incorrect, but that
apostrophe is.)
JMX Technology - Using it with Spring, and how it is
evolving (me)
Here's what I learnt at this talk:
-
I surveyed the audience to ask how many people were using
the J2SE 5.0 platform. About 60% of people were. I was a bit
embarrassed that I would be presenting new Java 6 features to
people who weren't even using 5.0 yet. (I wasn't surprised,
though. We do consistently hear developers tell us they'd love
to migrate to a more recent version but can't because their
organisation doesn't want to have to requalify everything, or
because some of their third party software isn't supported on
the more recent version.) -
The demo gods were very angry at this conference, and
smote me just as they had smitten every other session I saw
that presumed to include a demo. In my case I made a
trivial change to a web app and redeployed it, just as I had
rehearsed any number of times. But unlike all those times I
saw an exception scroll past too fast to see, and the app
server restarted! Since it takes a good two minutes to
restart I had to abandon that demo and waffle, what you
would have seen if the demo had worked.... The
reason for the problem is surely buried in the app server
logs but so far I have been too discouraged to
look. -
90 minutes is an awfully long time to speak, especially
if you still have some residual jet lag. I felt myself running
out of steam towards the end. -
People weren't aware that the release of the Java 6
platform was imminent. (It was coming up two days after my
talk, though I couldn't be that precise for fear of spoiling the
official announcement.) I suppose we had been talking for so
long about all the wonderful things that were coming later that
people assumed the later would be later than it
was.
Blog time
I'm no longer in Heathrow as I type this. I'm in a
days later. It's been a busy ten days. I'm wondering what sorts
of interesting philosophical things I could say about "blog time",
the fact that you're reading in continuous time my text written in
highly discontinuous time. Although I suppose that is true of
most non-trivial amounts of text, and generally less so of blogs
than of other media.
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