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CRaSH the shell for the Java Virtual Machine

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A presentation from Julien Viet - www.exoplatform.com

CRaSH is the open source shell for the JVM. The shell can be accessed by various ways, remotely using network protocols such as SSH, locally by attaching a shell to a running virtual machine or via a web interface. Commands are written Groovy and can be developed live making the extensibility of the shell easy with quick development cycles. Since the version 1.3, the REPL also speaks the Groovy language, allowing Groovy combination of command using pipes.

CRaSH comes with commands such as thread management, log management, database access and JMX. The session will begin with an introduction to the shell. The main part of the session will focus on showing CRaSH commands development with few examples, showing how easy and powerful the development is.

The audience will learn how to use CRaSH for their own needs: it can be a simple usage or more advanced like developing a command or embedding the shell in their own runtime like a web application or a Grails application.

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CRaSH the shell for the Java Virtual Machine

  1. 1. w w w . c r a s h u b . o r g CRaSH The shell for the JVM w w w . c r a s h u b . o r g Julien Viet exoplatform
  2. 2. w w w . c r a s h u b . o r g All semicolons characters appearing in this work are fictitious. Any resemblance to real characters, living or dead, is purely coincidental. Disclaimer
  3. 3. w w w . c r a s h u b . o r g http://www.julienviet.com / @julienviet 10 years of portal development (you know Portlets…) Working at eXoPlatform delivering enterprise social networks > me --verbose
  4. 4. w w w . c r a s h u b . o r g You can use @crashub or #crashub Try it online try.crashub.org/gists/ e61cb08d93746e576209 (pro tip follow @crashub) About this talk
  5. 5. w w w . c r a s h u b . o r g Once upon a time … Why did I do that ? what is CRaSH
  6. 6. w w w . c r a s h u b . o r g 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
  7. 7. w w w . c r a s h u b . o r g Modes Standalone / attach (download / brew / gvm) Embedded Connectors jvm (standalone & attach) ssh, telnet crash.js over websocket Concepts
  8. 8. w w w . c r a s h u b . o r g Standalone mode
  9. 9. w w w . c r a s h u b . o r g Return "hello world" Command script
  10. 10. w w w . c r a s h u b . o r g class helloworld { @Command String main() { return "Hello World" } } Command class
  11. 11. w w w . c r a s h u b . o r g class hello { @Command String world() { return "Hello World" } } Git style
  12. 12. w w w . c r a s h u b . o r g Command pipelining
  13. 13. w w w . c r a s h u b . o r g 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
  14. 14. w w w . c r a s h u b . o r g % thread ls | thread dump | mail -s "something you should look at" julien@julienviet.com Pipeline example
  15. 15. w w w . c r a s h u b . o r g <Void, Thread> is a producer <Thread, Object> is a pipe <String, String> is a pipe Pipeline example
  16. 16. w w w . c r a s h u b . o r g class daemon { @Command Pipe<Thread, Thread> main() { [provide: { if (it.daemon) context.provide(it) }] as Pipe<Thread, Thread> } } Pipe command
  17. 17. w w w . c r a s h u b . o r g # 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
  18. 18. w w w . c r a s h u b . o r g Read Eval Print Loop aka REPL
  19. 19. w w w . c r a s h u b . o r g By default the script REPL parses CLI familiar for most CLI users Script REPL
  20. 20. w w w . c r a s h u b . o r g very much like groovysh evaluates Groovy expressions DSL for creating CLI compose pipes and closures New Groovy REPL since 1.3
  21. 21. w w w . c r a s h u b . o r g % (thread.ls | thread.dump | mail { S="something you should look at” "admin@domain.com" })() Our command pipeline in Groovy
  22. 22. w w w . c r a s h u b . o r g More cool stuff
  23. 23. w w w . c r a s h u b . o r g Completers Renderers Keyboard: interruption / events Screen: streaming / styling More cool stuff
  24. 24. w w w . c r a s h u b . o r g Attach mode
  25. 25. w w w . c r a s h u b . o r g Embedding CRaSH
  26. 26. w w w . c r a s h u b . o r g Bootstrap: programmatic / Spring / Servlet Designed for embedding Lighweight : core jar about 600kb Modular : pay for what you need Virtual File System integration Embedding
  27. 27. w w w . c r a s h u b . o r g Ecosystem
  28. 28. w w w . c r a s h u b . o r g Created in Nov 2012 by Stephan Jaetzold Contributions by Burt Beckwith Recently updated to CRaSH 1.3 with additional features Grails Plugin
  29. 29. w w w . c r a s h u b . o r g And the story just begins
  30. 30. w w w . c r a s h u b . o r g Multi facet, powerful and extensible tool for all of us Join the community www.crashub.org @crashub crash-users@googlegroups.com Wrap up
  31. 31. w w w . c r a s h u b . o r g Extra slides
  32. 32. w w w . c r a s h u b . o r g 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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