www.exoplatform.com Learn how to provide a powerful command line interface to your JVM with CRaSH the shell for the Java Platform. CRaSH is an open source shell for extending and monitoring a Java Virtual Machine. The shell can be accessed by various means, either remotely using network protocols such as SSH or locally by attaching a shell to a running virtual machine. Commands are written in the Groovy language and can be developed live making the extensibility of the shell easy with quick development cycles. CRaSH comes with a bunch of commands such as thread management, log management, database access and JMX. The session will begin with an introduction to the shell, showing basic CRaSH features like auto completion and basic commands. The main part of the quickie will focus on showing how to develop CRaSH commands with several examples, showing how easy and powerful the development of a command can be. The target audience is pretty much anyone using a JVM. Attendees will learn how to install CRaSH, connect to an instance and develop a CRaSH command to interact with virtual machine resources or services.

1. CRaSH
TH E SH EL L FOR TH E J AVA PL ATFOR M
S E P T E M B E R 2 0 1 3
@julienviet
@defrancea

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JULIEN VIET
− Contact
− julien@julienviet.com
− @julienviet
− http://github.com/vietj
− Open source for 10 years
− Official mission: deliver enterprise grade portal
server
− Marseille JUG Leader
− Involved in Java Community Process

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WHAT IS EXO PLATFORM?
eXo Platform is an open
source social collaboration
software solution designed
for the Enterprise.
It is full featured, standard
based, extensible and has
an amazing design.
eXo Platform is featured in
Gartner's Magic Quadrant
for Horizontal Portal
Products 2012 as a User
eXperience Platform.

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ALAIN DEFRANCE
− Contact
− defrancea@gmail.com
− @alaindefrance
− http://github.com/defrancea
− Open source for 3 years
− Contributed to open source projects like
Crash
− Marseille JUG Leader

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BITTITAN
− SAAS Products
− MigrationWiz: Email migration
− SMTPLogic: SMTP gateway
− UserActivation: Easy onboarding to Office365
− Our blog
− http://blog.bittitan.com

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CRASH PROJECT
− Latest stable 1.2
− Work in progress 1.3
− Licensed under LGPL
− Compatibility
− Java 6+
− Groovy 1.7+

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KEY CONCEPTS
− Command Line Interface for JVM
− Create easily and quickly commands
− Compose commands into pipelines
− Connectors provide local or remote access

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MODULAR DESIGN
− Core, connectors, plugins
− Only use what you need
− Memory
− Dependencies

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CONNECTORS
− Defines shell interactions
− Asynchronous design
− Implemented by
− System.in / System.out
− Telnet
− SSH
− Web
− Attach

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PLUGIN ARCHITECTURE
− Keep core small and lightweight
− New features without impacting core
− Current plugins
− Authentication: simple, jaas, key, crowd, …
− Languages: java, groovy, ruby, …
− Services: mail, cron, …

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USER INTERFACE
− Interactive Real-Eval-Print-Loop
− SSH asynchronous execution
− Cron based execution (1.3)

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POLYGLOT
− Leverage polyglot JVM ecosystem
− Groovy
− Commands
− REPL (1.3)
− Java
− Commands (1.3)
− Ruby work in progress

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EXECUTION MODES
− Standalone
− Attach to a running JVM
− Embedded
− Servlet listener
− Spring
− Guice
− Grails
− VisualVM

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BASE COMMANDS
− Covers JVM packages
− system
− jdbc
− jndi
− jmx
− Utilities: filter, sort, egrep, sleep

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STANDALONE DEMO

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JNDI/JDBC/JPA
ATTACH
DEMO

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WRITING A COMMAND
public class mycommand {
@Command
@Usage(“the command”)
public void main(
@Usage(“foo option”)
@Option(names=[ “foo”]) String foo,
@Usage(“command arguments”)
@Argument List<String> args) {
…
}
}
% mycommand –foo the_option value1 value2

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EMBEDDED
− Trivial to embed
− Programmatic
− Spring
− Guice
− Servlet listener
− Levels
− Embed
− Virtual file system

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EMBEDDED BY

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SPRING EMDEDDED
TWITTER COMMAND
DEMO

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GIT LIKE COMMAND
public class git {
@Command
public void add(…) {…}
@Command
public void commit(…) {…}
…
}
% git add .
% git commit –m “feature implemented”

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TYPES
− String, primitive types, enums
− Converter
− properties, jmx object name …
− Completer
− java.io.File
− system property name
− enums
− …

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COMMAND PIPE
jmx find
ObjectName Map
jmx get sort

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COMMAND PIPE
public class wc {
@Command
public PipeCommand<String, Integer>) main() {
return new PipeCommand<String, Integer>() {
int count = 0;
public void provide(String s) {
count += s.split(“n”).length;
}
public void close() {
context.provide(count);
}
}
}
}

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JMX PIPE
DEMO

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MAIL/CRON
DEMO

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READ-EVAL-PRINT-LOOP
− Feature of 1.3
− Polyglot

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REPL
DEMO

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WRAP UP
− A multi facet, powerful and extensible tool
for all of us
− Try online : try.crashub.org
− Reach us at
− crashub.org
− @crashub
− crash-users@googlegroups.com