Torsten Curdt
<vafer/>.org tcurdt@apache.org
Rapid Application
Development
with Cocoon
javaflow and the
compiling classloader
Cocoon GetTogether 2005,
Amsterdam

about me : 2
:
• with Cocoon since 1.x
• member of the Cocoon PMC
• member of the Jakarta PMC
• ASF member

quote : 3
:
“Rapid Application Development is
exactly the opposite of what Cocoon
provided a fears ago - but gladly
enough times have changed”
Torsten Curdt

agenda : 4
:
• general environment hints
• Cocoon features for RAD
• web application and IDE config
• live demonstration
• behind the scenes
• overview of jci and javaflow

hints : 5
:
• stripped down version of Cocoon
• build the source jars
• relocate the webapp with the
COCOON_WEBAPP_HOME
environment variable
• use “cocoon servlet-debug”

features : 6
:
• compiling + reloading of classes
• compiling + reloading of javaflow
• compiling + reloading of components
• reloading of jars

map:classpath : 7
:
<map:components>
...
<map:classpath>
<class-dir src=”...”/>
<src-dir src=”...”/>
<lib-dir src=”...”/>
</map:classpath>
...

store : 8
:
<map:components>
...
<map:classpath>
<class-dir src=”...”>
<store class=”...”/>
</class-dir>
</map:classpath>
...

eclipse : 9
:
DEMO

hmmm : 10
:
So how does it
work?

sitemap : 11
:
• own component manager
• can have a dedicated classpath
• uses a paranoid* classloader
*parent-last classloader

reloading : 12
:

adding flow : 13
:
• resources transformed on-the-fly
• similar to pipelines

...but! : 14
:
• does not help for core development
• be careful on a live system upgrade
• object types defined per classloader

dimensions : 15
:

gotchas : 16
:
• objects in sessions
• parent component manager
component interactions
• old continuations

commons : 17
:
• commons jci does the
• monitoring
• compilation
• commons javaflow provides
• java continuations
• cocoon javaflow block
• evolved out of cocoon 2.1
• now being used in cocoon trunk

cocoon block : 18
:
• flow interpreter
• flow object model
• base classes
• integration with CForms

example : 19
:
public class MyFlow extends
AbstractContinuable {
public void run() {
...
sendPageAndWait(
”page”, data);
...
}

jci : 20
:
• compiler abstraction
• supports eclipse, janino, groovy
• filesystem monitoring
• events for create, change and delete
• compiling/reloading class loader
http://jakarta.apache.org/commons/sandbox/jci

jci API : 21
:
CompilationResult result =
compiler.compiler(
classNames,
new FileResourceReader(dir),
new MemoryResourceStore());
if (result.getErrors()
.length > 0) { ...

jci API : 22
:
FilesystemAlterationMonitor
fam = new F..A..M();
fam.start();
fam.addListener(
new CompilingListener(
dir));

future : 23
:
• almost ready for a release
(94% testcase coverage!!)
• better dependencies support
• adding more compilers
• javac, pizza, jikes, gcj
• maven might switch to jci

javaflow : 24
:
• java continuations through
bytecode instrumentation
• works hand in hand with jci
• ant-task for jar/class rewriting
• supports serialization(!!)
http://jakarta.apache.org/commons/sandbox/javaflow

javaflow API : 25
:
Continuation continuation =
Continuation.startWith(
new Calculator());
...
Continuation.continueWith(
continuation);

continuations : 26
:

instrumentation : 27
:

scalability : 28
:
• the deeper your flow, the more
memory used per continuation
• increases linearly
• avoid recursion
• the more method calls, the more
overhead
• can be heavily optimized

limitations : 29
:
• suspend in synchronized blocks
• suspend in a catch/finally

future plans : 30
:
• remove current limitations
• call graph analysis for optimization
• switching from BCEL to ASM(?)
• support for external suspends(?)
• talking with the guys from RIFE
• release within the next few months

summary : 31
:
• auto-compiling and reloading of
• classes
• javaflow
• components
• full IDE support
• debugging
• refactoring
• (potential) serialization support
• persisting continuations across restarts
• session and flow replication

thanks : 32
:
questions?