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© Copyright Azul Systems 2016
© Copyright Azul Systems 2015
@speakjava
JDK 9: Big Changes To Make Java Smaller
Simon RitterDeputy CTO, Azul Systems
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© Copyright Azul Systems 2016
API Structural Changes
© Copyright Azul Systems 2016
API Classification
Supported, intended for public use– JCP specified: java.*, javax.*– JDK specific: some com.sun.*, some jdk.*
Unsupported, not intended for public use– Mostly sun.*– Most infamous is sun.misc.Unsafe
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© Copyright Azul Systems 2016
General Java Compatability Policy
If an application uses only supported APIs on version N of Java it should work on version N+1, even without recompilation
Supported APIs can be removed–But only with advanced notice
JDK 8 has 18 interfaces, 23 classes, 64 fields, 358 methods and 20 constructors that have been deprecated
–None have been removed–Until now
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© Copyright Azul Systems 2016
JDK 9: Incompatible Changes
Encapsulate most JDK internal APIs Remove a small number of supported APIs
– 6 in total, all add/remove PropertyChangeListener– Already flagged in JSR 337 (Java SE 8), JEP 162
Change the binary structure of the JRE and JDK New version string format A single underscore will no longer be allowed as an
identifier in source code
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Removed In JDK 9
Endorsed standard API override mechanism Extension mechanism
No longer required now we have a module system
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© Copyright Azul Systems 2016
Most Popular Unsupported APIs
1. sun.misc.BASE64Encoder
2. sun.misc.Unsafe
3. sun.misc.BASE64Decoder
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Oracle dataset based on internal application code
© Copyright Azul Systems 2016
JDK Internal API Classification
Non-critical– Little or no use outside the JDK– Used only for convenience (alternatives exist)
Critical– Functionality that would be difficult, if not impossible to
implement outside the JDK
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© Copyright Azul Systems 2016
JEP 260 Proposal
Encapsulate all non-critical JDK-internal APIs Encapsulate all critical JDK-internal APIs, for which
supported replacements exist in JDK 8 Do not encapsulate other critical JDK-internal APIs
– Deprecate these in JDK 9– Plan to encapsulate or remove them in JDK 10– Provide command-line option to access encapsulated
critical APIs
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© Copyright Azul Systems 2016
Reviewing Your Own Code
jdeps tool– Introduced in JDK 8, improved in JDK 9– Maven jdeps plugin
jdeps –jdkinternals path/myapp.jar
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path/myapp.jar -> /opt/jdk1.8.0/jre/lib/rt.jar <unnamed> (myapp.jar) -> sun.misc.Unsafe -> ...
© Copyright Azul Systems 2016
Project Jigsaw And Modules
© Copyright Azul Systems 2016
Goals For Project Jigsaw
Make Java SE more scalable and flexible– Internet of Things– Microservices
Improve security, maintainability and performance
Simplify construction, deployment and maintenance of large scale applications
Eliminate classpath hell
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© Copyright Azul Systems 2016
Module Fundamentals
Module is a grouping of code– For Java this is a collection of packages
Modules can contain other things– Native code– Resources– Configuration data
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com.azul.zoop
com.azul.zoop.alpha.Namecom.azul.zoop.alpha.Positioncom.azul.zoop.beta.Animalcom.azul.zoop.beta.Zoo
© Copyright Azul Systems 2016
Module Declaration
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module com.azul.zoop {}
module-info.javacom/azul/zoop/alpha/Name.javacom/azul/zoop/alpha/Position.javacom/azul/zoop/beta/Animal.javacom/azul/zoop/beta/Zoo.java
© Copyright Azul Systems 2016
Module Dependencies
module com.azul.zoop { requires com.azul.zeta;} com.azul.zoop
com.azul.zeta
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Module Dependencies
module com.azul.app { requires com.azul.zoop; requires java.sql;}
com.azul.app
com.azul.zoop java.sql
© Copyright Azul Systems 2016
Module Dependency Graph
com.azul.app
java.base
java.sqlcom.azul.zoop
com.azul.zetajava.xml java.logging
explicitimplicit
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Readability v. Dependency
com.azul.app
java.sql
java.logging
module java.sql { requires public java.logging;}
Driver d = …Logger l = d.getParentLogger();l.log(“azul’);
Implied readability
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Module Implied Readability Graph
com.azul.app
java.base
java.sqlcom.azul.zoop
com.azul.zetajava.xml java.logging
explicitimplicitimplied
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Package Visibility
module com.azul.zoop { requires com.azul.zeta; exports com.azul.zoop.alpha; exports com.azul.zoop.beta to com.azul.app;}
com.azul.zoop
com.azul.zoop.alpha
com.azul.zoop.betacom.azul.zoop.thetacom.azul.app only
© Copyright Azul Systems 2016
More Package Visibility
weak module com.azul.zoop { requires com.azul.zeta;}
com.azul.zoop
com.azul.zoop.alphacom.azul.zoop.beta com.azul.zoop.theta
© Copyright Azul Systems 2016
Even More Package Visibilitymodule com.azul.zoop { requires com.azul.zeta; exports com.azul.zoop.alpha; exports com.azul.zoop.beta to com.azul.app; exports private com.azul.theta;}
com.azul.zoop
com.azul.zoop.thetaREFLECTIONGENERAL
com.azul.zoop.alpha
com.azul.zoop.betacom.azul.app only
© Copyright Azul Systems 2016
Accessibility
For a package to be visible– The package must be exported by the containing module– The containing module must be read by the using module
Public types from those packages can then be used
com.azul.zoopcom.azul.app
reads
© Copyright Azul Systems 2016
Java Accessibility (pre-JDK 9)
publicprotected<package>private
© Copyright Azul Systems 2016
Java Accessibility (JDK 9)
public to everyonepublic, but only to specific modulespublic only within a module protected<package>private
public ≠ accessible (fundamental change to Java)
© Copyright Azul Systems 2016
JDK 8 Dependencies
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JDK 9 Platform Modules
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java.se
java.compact3
java.compact2
java.compact1
java.scripting
java.instrument
java.base
java.logging
java.sql
java.sql.rowset
java.xml
java.desktop
java.rmi
java.prefsjava.datatransfer
java.compiler
java.management
java.security.jgss
java.naming
java.security.sasl
All modules depend on java.base
no impliedreadability=
© Copyright Azul Systems 2016
JDK 9 Platform Modules
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java.se.ee java.se
java.xml.bind
java.corba
java.compiler
java.desktop
java.annotations.common
java.rmi
java.datatransfer
java.management
java.xml.ws
java.naming
java.transaction
java.activation
All modules depend on java.base
© Copyright Azul Systems 2016
Using Modules
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Module Path
$ javac –modulepath dir1:dir2:dir3
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Compilation With Module Path
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$ javac –modulepath mods –d mods \ src/module-info.java \ src/com/azul/zoop/alpha/Name.java
mods/module-info.classmods/com/azul/zoop/alpha/Name.class
src/module-info.javasrc/com/azul/zoop/alpha/Name.java
© Copyright Azul Systems 2016
Application Execution
-modulepath can be abbreviated to -mp
$ java –mp mods –m com.azul.app/com.azul.app.Main
Azul application initialised!
module name main class
© Copyright Azul Systems 2016
Packaging With Modular JAR Files
mods/module-info.classmods/com/azul/app/Main.class
$ jar --create --file mylib/app.jar \ --main-class com.azul.app.Main \ -C mods .
module-info.classcom/azul/app/Main.class
app.jar
© Copyright Azul Systems 2016
JAR Files & Module Information
$ jar --file mylib/app.jar –pName: com.azul.zoopRequires: com.azul.zeta java.base [MANDATED] java.sqlMain class: com.azul.zoop.Main
© Copyright Azul Systems 2016
Application Execution (JAR)
$ java –mp mylib:mods –m com.azul.app
Azul application initialised!
© Copyright Azul Systems 2016
LinkingModular run-time
image
…confbin
jlink
$ jlink --modulepath $JDKMODS \ --addmods java.base –output myimage
$ myimage/bin/java –[email protected]
© Copyright Azul Systems 2016
Linking An Application
$ jlink --modulepath $JDKMODS:$MYMODS \ --addmods com.azul.app –output myimage
$ myimage/bin/java –[email protected]@[email protected]@[email protected]@[email protected]
Version numbering forinformation purposes only“It is not a goal of the module system to solve the version-
selection problem”
© Copyright Azul Systems 2016
Application Migration
© Copyright Azul Systems 2016
Typical Application (JDK 8)
jarjar
jar
JDK
jar
jarjarjar jar
jarjar
jar
jar
Cla
sspa
th
© Copyright Azul Systems 2016
Typical Application (JDK 9)
jarjar
jar
modulejava.base
modulejava.desktop
modulejava.datatransfer
modulejava.xml
jar
jarjarjar jar
jarjar
jar
jar
Unnamed module
© Copyright Azul Systems 2016
Sample Application
myapp.jar
libgl.jar
mylib.jar
gluegen.jar jogl.jar
modulejava.base
modulejava.desktop
modulejava.datatransfer
modulejava.xml
© Copyright Azul Systems 2016
Run Application With Classpath
$ java –classpath \ lib/myapp.jar: \ lib/mylib.jar: \ lib/libgl.jar: \ lib/gluegen.jar: \ lib/jogl.jar: \ myapp.Main
© Copyright Azul Systems 2016
Sample Application
modulemyapp.ja
r
libgl.jar
modulemylib.jar
gluegen.jar jogl.jar
modulejava.base
modulejava.desktop
modulejava.datatransfer
modulejava.xml
© Copyright Azul Systems 2016
Application module-info.java
module myapp { requires mylib; requires java.base; requires java.sql; requires libgl; ???? requires gluegen; ???? requires jogl; ????}
© Copyright Azul Systems 2016
Sample Application
modulemyapp.ja
r
modulelibgl.jar
modulemylib.jar
modulegluegen.jar
modulejogl.jar
modulejava.base
modulejava.desktop
modulejava.datatransfer
modulejava.xml
© Copyright Azul Systems 2016
Automatic Modules
Real modules Simply place unmodified jar file on module path
– Rather than classpath No changes to JAR file Module name derived from JAR file name Exports all its packages
– No selectivity Automatically requires all modules on the module path
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© Copyright Azul Systems 2016
Application Module Dependencies
modulemyapp.ja
r
modulelibgl.jar
modulemylib.jar
modulegluegen.jar
modulejogl.jar
modulejava.base
modulejava.desktop
modulejava.datatransfer
modulejava.xml
ImplicitExplicit
© Copyright Azul Systems 2016
Run Application With Modules
$ java –classpath \ lib/myapp.jar: \ lib/mylib.jar: \ lib/libgl.jar: \ lib/gluegen.jar: \ lib/jogl.jar: \ myapp.Main
$ java –mp mylib:lib –m myapp
© Copyright Azul Systems 2016
Summary
© Copyright Azul Systems 2016
Summary
Modularisation is a big change for Java– JVM/JRE rather than language/APIs
Potentially disruptive changes to exposure of non-public APIs– Is it safe?
Developing modular code will require some learning– Not a huge change, though
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© Copyright Azul Systems 2016
Zulu.org
Azul binary distribution of OpenJDK source code Passed all TCK tests Completely FREE!
– Pay us if you’d like enterprise level support Just announced: Embedded Zulu support for ARM 32-bit
– Intel already supported– “Requires no licensing fee”
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© Copyright Azul Systems 2016
Further Information
openjdk.java.net openjdk.java.net/jeps openjdk.java.net/projects/jigsaw jcp.org
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© Copyright Azul Systems 2016
© Copyright Azul Systems 2015
@speakjava
Thank You!
Simon RitterDeputy CTO, Azul Systems
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