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CRaSH
The shell for the JVM
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Julien Viet
exoplatform

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All semicolons characters appearing in this work
are fictitious. Any resemblance to real
characters, living or dead, is purely
coincidental.
Disclaimer

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http://www.julienviet.com / @julienviet
10 years of portal development (you know
Portlets…)
Working at eXoPlatform delivering enterprise
social networks
> me --verbose

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You can use @crashub or #crashub
Try it online try.crashub.org/gists/
e61cb08d93746e576209 (pro tip follow
@crashub)
About this talk

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Once upon a time …
Why did I do that ? what is
CRaSH

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Latest 1.2.9 / 1.3.0-cr5
Java 6+ / Groovy 1.7+
Base commands : jdbc, jmx, thread, jpa, log, etc..
Extensions: mail, cron
CRaSH

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Modes
Standalone / attach (download / brew / gvm)
Embedded
Connectors
jvm (standalone & attach)
ssh, telnet
crash.js over websocket
Concepts

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Standalone mode

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Return "hello world"
Command script

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class helloworld {
@Command
String main() {
return "Hello World"
}
}
Command class

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class hello {
@Command
String world() {
return "Hello World"
}
}
Git style

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Command pipelining

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Write programs that do one thing and do it well.
Write programs to work together. Write
programs to handle text streams, because
that is a universal interface.
- Ken Thompson
Unix philosophy

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% thread ls | thread dump | mail -s
"something you should look at"
julien@julienviet.com
Pipeline example

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<Void, Thread> is a producer
<Thread, Object> is a pipe
<String, String> is a pipe
Pipeline example

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class daemon {
@Command
Pipe<Thread, Thread> main() {
[provide: {
if (it.daemon)
context.provide(it)
}] as Pipe<Thread, Thread>
}
}
Pipe command

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#
log ls -f org.crsh.* | log send -m "hello"
#
system propls | filter -p NAME:java.* | sort -f
NAME
#
jmx query -p
java.lang:type=GarbageCollector,name=* | jmx
get -a Name -a CollectionCount -a
CollectionTime
Other examples

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Read Eval Print Loop aka REPL

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By default the script REPL parses CLI
familiar for most CLI users
Script REPL

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very much like groovysh
evaluates Groovy expressions
DSL for creating CLI
compose pipes and closures
New Groovy REPL since 1.3

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% (thread.ls | thread.dump | mail {
S="something you should look at”
"admin@domain.com"
})()
Our command pipeline in Groovy

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More cool stuff

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Completers
Renderers
Keyboard: interruption / events
Screen: streaming / styling
More cool stuff

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Attach mode

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Embedding CRaSH

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Bootstrap: programmatic / Spring / Servlet
Designed for embedding
Lighweight : core jar about 600kb
Modular : pay for what you need
Virtual File System integration
Embedding

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Ecosystem

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Created in Nov 2012 by Stephan Jaetzold
Contributions by Burt Beckwith
Recently updated to CRaSH 1.3 with additional
features
Grails Plugin

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And the story just begins

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Multi facet, powerful and extensible tool for all of
us
Join the community
www.crashub.org
@crashub
crash-users@googlegroups.com
Wrap up

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Extra slides

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new UIBuilder().table {
header {
label("key")
label("value")
}
System.properties.each { k,v ->
row {
label(k).style(Color.red.fg());
label(v).style(Color.blue.fg())
}
}
}
Building more complex UI with a DSL