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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" [email protected]
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” "[email protected]" })()
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 [email protected]
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
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