Java 9 / Jigsaw - LJC / VJUG session (hackday session)

Java 9 / Jigsaw
Modularisation & more

Presenters
Simon Maple
@sjmaple
Mani Sarkar
@theNeomatrix369
Hendrik Ebbers
@hendrikebbers

Our guest
Heather VanCura
@heathervc

Agenda
- Session 1: Introduction
- What is meant by Modularisation in Java 9?
- Session 2: JLink
- Lunch break: lunch + 10/15 minute optional session
- Fundamentals and background
- JSRs / JEPs playing a role
- Modularisation of OpenJDK sources (JEP 201 and related JEPs)
- Modularisation of Runtime Images (JEP 220 and related JEPs)
- Modularisation of Java Packages and Application Packaging (JEP 275 and related JEPs)
- Feature distribution
- Why modularisation?
- So many more topics to cover!
- Visualise your dependencies!
- Session 3: Migrating non-modular app to Java 9 or JShell
- Feedback
- Contribution
- Resources

How to share your (live) feedback with us?
Discussion/technical corner, share your thoughts, code snippets,
issues, feedback with us while you code away...
https://goo.gl/oytFzX
We have left a few
issues for you to find,
investigate, solve, report
to us or the OpenJDK /
JDK9 team

Setup
Is everyone setup, and ready to go?
https://git.io/v9UJ8
You have this link via email / meetup message!

Session 1: Introduction: Java 9 modularisation
15 minutes

What is meant by Modularisation in Java 9?
JDK
module java.base
package java.io
class Console
...
package java.lang
class String
...
module java.logging
package java.util.logging
class FileHandler
class LogManager
...
module java.sql
package java.sql
class Connection
class SqlData
...
Java, the language: split into modules
modules...
packages...
classes...

java.base
java.sql
other
modules...
java.logging
Java, the language: dependency graph
java.xml
implicit implicit
explicit
(requires)
explicit
(requires)
implicit
JDK

Java, the language: dependency graph
java.base
java.sql
other
modules...
java.logging java.xml
implicit implicit
explicit
(requires)
explicit
(requires)
implicit
JDK
Our Java
applications
explicit
(requires)
explicit
implicit

Pre-Java 9
Java 9/Jigsaw
src/main/java
package a.b.c
class p
class q
package m.n.o
class s
class t
src/main/java
module a.b.c
package a.b.c
class p
class q
module m.n.o
package m.n.o
class s
class t
Structure of
a typical
Java app.
containing
packages...
Create your own
modules
containing
packages, classes...

Typical package structure Modules contain packages
Credits to Paul Bakker & Sander Mak
package books.api.entities
classes
package bookstore.api.service
What is looks like from the file system?

Typical package structure Modules contain packages
Credits to Paul Bakker & Sander Mak
contains module
visibility
(readability) &
dependency info
module books.api contains
package books.api.entities
package books.api.service
modules
What is looks like from the file system?

module com.abc {
requires com.abc.pqr;
requires transitive com.xyz.abc;
exports com.abc.def.alpha;
exports com.abc.pqr.beta to
com.ijk.mno,
com.lmn.stu;
uses java.network.Driver;
provides java.sql.Driver with com.mno.def.Driver;
}
module
definition
defines dependencies of module, to modules
com.abc.pqr & com.xyz.abc
transitive keyword defines
implicit dependency
module name
How is module dependencies are defined in Java 9?
module-info.java

module com.abc {
com.ijk.mno,
com.lmn.stu;
}
module
definition
make all & only public types in specified
packages available to other modules
module name
… or make available
to specified modules
module-info.java

module com.abc {
com.ijk.mno,
com.lmn.stu;
}
module-info.java
module
definition
this module publishes
a service provider
this module uses a service provider
published by another module
module name

Session 1: Hands-on: Java 9 modularisation
60 minutes
https://github.com/AdoptOpenJDK/jdk9-jigsaw/tree/master/session-1-jigsaw-intro

Session 1: feedback
15 minutes

Lunch break
60 minutes
Short 10/15 minutes covering intro/background/fundamentals (talk while having a bite of food and drink)

A bit of fundamentals and background before we get to the answer

modularisation
Pre-Java 9 Java 9
Anomalies
OpenJDK& JDK

How we perceive the JDK/JRE from a developer’s / end-user’s perspective?
JDK or
JRE
IBM
Other
vendors
Oracle download
Create
Client
Apps
distribute
Client
Apps +
bundle
JRE

How the maintainers of Java perceive it?
Distribute
built apps
+ bundle
JDK
IBM
Other
vendors
Oracle build downloadOpenJDK JDK

Modularisation of OpenJDK sources (JEP 201 and related JEPs)
Binary
compatible
JDK
re-organise rebuild
OpenJDK
source
Refactored
OpenJDK
source
Repository
JDK
re-organise
Improved layout of
source folders in
the JDK repository

Modularisation of Runtime Images (JEP 220 and related JEPs)
Binary
compatible
JDK
re-organise rebuild
Runtime
JDK
Optimised
(modular)
JDK
Runtime
Traditional
Runtime JDK
Image
re-organise
A more compact
Runtime JDK Image

Modularisation of Java Packages and Application Packaging (JEP 275 and related JEPs)
Modular Java 9
application +
custom JDK
compiles creates
Modularised
JDK Runtime
Modular
Java 9
source
JLink Smaller JDK footprint
Java 9
applicationcompiles creates
Modularised
JDK Runtime
Non-modular
Java 9 source
Binary compatible
creates

JSR 376: Java Platform Module System played the primary role
http://openjdk.java.net/projects/jigsaw/spec/

JEPs that lead to all the new features in Java 9 (including
Jigsaw):
- 200: The Modular JDK
- 201: Modular Source Code
- 220: Modular Run-Time Images (depends on JEP 162)
- 260: Encapsulate Most Internal APIs (no dependencies)
- 261: Module System (dependens on JEP 220, related to JEP 238)
- 282: jlink: The Java Linker (replaces implementation of JEP 220)
- 275: Modular Java Application Packaging
- 222: jshell: The Java Shell (Read-Eval-Print Loop)
- 193: Variable Handles
- 110: HTTP 2 Client
- 238: Multi-Release JAR Files
- 158: Unified JVM Logging
- G1 related JEPs (3)
- JEPs related to a number of security improvements
- JEPs related to a number of platform improvements
- >>> Many, many more JEPs, see the Java 9 JEPs list for further details <<<

JDK 9& Jigsaw feature distribution
...
Other
JDK 9
features
Jigsaw
...
...
...
... ... ... ...
...
...
...
...
...
...
...
...

Why Modularisation in Java 9?
But, why?

It’s been worked on for about a decade:
- Encapsulation (hiding away what’s not intended or necessary for public use)
- JDK internal APIs (sun.misc.unsafe, security, etc…)
- Our APIs
- Decluttering of code bases (loose coupling & high cohesion)
- OpenJDK sources
- JDK sources
- Our Java App sources (post migration and refactoring)
- Customised runtime JDK (smaller footprint)
- Highly desirable for IoT, arduino/embedded devices, etc…
- Improve distribution and runtime performance
- OSGi has it, why not in native Java?
- Any more?
Why Modularisation in Java 9?

Not everything can be covered but let’s find out about these topics:
- open module
- open package
- named and unnamed modules
- difference between classpath and module path
- automatic module names
- kill switch (remove Jigsaw restrictions)
- a CLI flag passed to java: java --permit-illegal-access …
- Jlink CLI option: --launcher
- and many more topics...
So many things to cover!

https://github.com/accso/java9-jigsaw-depvis
Visualise your dependencies!

Session 2: Introduction: JLink
10 minutes

Create a package
distributable, that
runs on any platform,
but needs a platform
specific JDK
JDK (javac)
Your App
packages
& classes
Your App
package
(distributable)
JVM, the
Platform
Java, the
language
(packages &
classes)
Any JRE/JDK
compiles
creates
Pre-Java 9
depends on (needs), to run

JDK
modules
JLink
JVM, the
Platform
Java, the
language (JDK
modules)
Your App
modules
Create standalone
distributable (smaller
footprint), that runs
on a specific platform
Your App
modules
JDK compiles
creates
Java 9

Session 2: Hands-on: JLink
40 minutes
https://github.com/AdoptOpenJDK/jdk9-jigsaw/tree/master/session-2-jlink

Session 2: feedback
10 minutes

Session 3: Introduction: Migration or JShell
15 minutes

Session 3: Introduction: Migration or JShell
Hendrik Ebbers
@hendrikebbers
Over to
Hendrik

Session 3 hands-on: Migration or JShell
60 minutes
https://github.com/AdoptOpenJDK/jdk9-jigsaw/tree/master/session-3-jshell

Session 3 & overall: feedback
15-30 minutes

Contribute
Don’t like something or like something a lot,
want to contribute to make things better?
https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/content/en/how-to-navigate/how_to_contribute_to_adopt_openjdk_and_openjdk.html

Feedback
We value your feedback, make Java better
with your constructive feedback
https://adoptopenjdk.gitbooks.io/adoptopenjdk-getting-started-kit/content/en/feedback.htm
l

Resources
Want to know about the other features of Java 9:
https://github.com/AdoptOpenJDK/jdk9-jigsaw/blob/master/Java-9-Resources.md

Thank you to all
Thank you for your continued support
9
@virtualJug
@ljcjug
@hackthetower
@adoptopenjdk
@openjdk
@jcp_org
@java

Java 9 / Jigsaw - LJC / VJUG session (hackday session)

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