Jigsaw - The Modular JDK PT.JUG - 03/12/2015 João Carvalho johnkarva jcarvalho Sérgio Silva sergiofbsilva sergiofbsilva

FenixEdu

Agenda What’s new in JDK 9? Project Jigsaw How can I prepare my application?

Disclaimer Most of the information shown in this presentation is based on multiple talks in JavaOne 2015 and Devoxx BE 2015. This presentation is focused on features that are under active development, and as such, a lot can change before the final release.

JDK 9

JDK 9 Flexibility and scalability Security and maintainability improvements Easing the construction, maintainability, deployment and upgrade of large scale applications Enabling performance improvements Coming to you, March 2017 (postponed on Tuesday)

JDK 9 Highlights ● VarHandles (JEP 193) ● The Modular JDK* (JEP 200) ● Modular Source Code (JEP 201) ● Modular Run-Time Images (JEP 220) ● jshell (JEP 222) ● New Version-String (JEP 223) ● UTF-8 Property Files (JEP 226) ● Multi-Release JAR Files (JEP 238) ● Cross-Release Compilation (JEP 247) ● Make G1 the default GC (JEP 248) * = Not yet targeted ● Compact Strings (JEP 254) ● Stack-Walking API (JEP 259) ● Encapsulate Most Internal APIs* (JEP 260) ● Module System* (JEP 261) ● Factory Methods for Collections (JEP 269) ● Dynamic Linking (JEP 276) ● Enhanced Deprecation* (JEP 277) ● Indify String Concatenation* (JEP 280)

JDK APIs

● Supported: ○ JCP Standard: java.*, javax.* ○ JDK-Specific: com.sun.*, some jdk.* ● Unsupported: ○ JDK Internal: sun.* ● Public, Supported APIs are generally backwards-compatible Categories of APIs on the JDK

Breaking APIs Judge risk and impact Good communication Provide replacement APIs or workarounds Provide upgrade paths and guides

Incompatible JDK 9 Changes ● Encapsulate most internal APIs (JEP 260) ● Remove the JRE ● Changing the binary structure of the JDK ● Removed endorsed standards override and extension mechanisms ● Removed bootclasspath ● New version-string format ● No more ‘_’ variables!

Most used JDK-internal APIs ● sun.misc.BASE64Encoder ● sun.misc.BASE64Decoder ● sun.misc.Unsafe ● sun.reflect.* ● com.sun.image.* ● sun.security.* ● sun.net.* ● Non-critical ○ Only used internally ○ Used for convenience ● Critical ○ Difficult to implement outside the JDK

JEP 260 ● Encapsulate non-critical APIs ● Encapsulate critical internal APIs with replacements in 8 ● Do not encapsulate critical APIs ○ Deprecate in 9 ○ Plan to remove in 10 ● sun.misc.Unsafe ● sun.misc.Signal ● sun.misc.SignalHandler ● sun.misc.Cleaner ● sun.reflect.Reflection:: getCallerClass ● sun.reflect.ReflectionFactory

http://alexanderskoog.deviantart.com/

-XaddExports -XaddExports:java.base/sun.security=ALL_UNNAMED

-XaddExports -XaddExports:java.base/sun.security=ALL_UNNAMED Module Package Target

What can I do to prepare? Remove usages of JDK-internal APIs Check for code that relies on the JDK version number format Check for usages of underscore as an identifier Test your code with the early access builds

Jigsaw

Why Jigsaw ? ● JAR/Classpath Hell ○ unfulfilled dependencies will only be discovered at runtime. NoClassDefFoundError ● Weak Encapsulation Across Packages ○ Across package boundaries there is only one visibility: public ○ class loader folds all loaded packages into one big ball of mud ■ “jar file is a filesystem on a stick” - Mark Reinhold (lead Jigsaw Oracle developer)

Why Jigsaw ? ● Rigid Java Runtime ○ Java8 introduced compact profiles but are still cluttered ○ large runtime image footprint (not ready for IoT and server containers) ● Startup Performance ○ class loading executes a linear scan of all JARs on the class path

Jigsaw - What gives ? The jdk9 itself built using modules ● Reliable Configuration ○ module/classes dependency graph available at any time (even runtime) ● Strong Encapsulation ○ A class that is private to a module should be private in exactly the same way that a private field is private to a class. In other words, module boundaries should determine not just the visibility of classes and interfaces but also their accessibility.

Jigsaw - What gives ? ● Improved Security And Maintainability ○ strong encapsulation of module internal API ○ critical code is now effectively hidden ○ maintenance easier as a module’s public API can more easily be kept small. ● Improved Performance ○ optimization techniques can be more effective when it is known that a class can refer only to classes in a few other specific components rather than to any class loaded at run time ● Scalable Platform ○ cherry pick the functionality needed and create their own JDK ○ important for small devices as well as for containers

Jigsaw - What is a Module ? ● Each module must declare ○ Which packages it exports ○ Which modules it requires ○ Implicit requires module java.base

Jigsaw - What is a Module ? org.fenixedu.foo.alpha.Alpha org.fenixedu.foo.alpha.AlphaFactory org.fenixedu.foo.alpha.AlphaService org.fenixedu.foo.beta.Beta org.fenixedu.foo.beta.BetaFactory org.fenixedu.foo.beta.BetaService org.fenixedu.foo.internal.GreekUtil fenixedu-foo.jar

Jigsaw - What is a Module ? org.fenixedu.foo.alpha.Alpha org.fenixedu.foo.alpha.AlphaFactory org.fenixedu.foo.alpha.AlphaService org.fenixedu.foo.beta.Beta org.fenixedu.foo.beta.BetaFactory org.fenixedu.foo.beta.BetaService org.fenixedu.foo.internal.GreekUtil fenixedu-foo.jar ├── org └── fenixedu └── foo ├── alpha │ ├── Alpha.java │ ├── AlphaFactory.java │ └── AlphaService.java ├── beta │ ├── Beta.java │ ├── BetaFactory.java │ └── BetaService.java └── internal └── GreekUtil.java public classes in a jar file

Jigsaw - Create a module org.fenixedu.foo.alpha.Alpha org.fenixedu.foo.alpha.AlphaFactory org.fenixedu.foo.alpha.AlphaService org.fenixedu.foo.beta.Beta org.fenixedu.foo.beta.BetaFactory org.fenixedu.foo.beta.BetaService org.fenixedu.foo.internal.GreekUtil org.fenixedu.foo // module-info.java module org.fenixedu.foo { // requires java.base; exports org.fenixedu.foo.alpha; exports org.fenixedu.foo.beta; } ├── module-info.java └── org └── fenixedu └── foo ├── alpha │ ├── Alpha.java │ ├── AlphaFactory.java │ └── AlphaService.java ├── beta │ ├── Beta.java │ ├── BetaFactory.java │ └── BetaService.java └── internal └── GreekUtil.java

Jigsaw - Create a module # compiling module > javac -d mods/org.fenixedu.foo $(find org.fenixedu.foo/src -name '*. java') # package module as a module jar file > jar --create --file mlib/foo.jar -C mods/org.fenixedu.foo .

Jigsaw - Create a module # listing jar files > jar tvf mlib/foo.jar META-INF/ META-INF/MANIFEST.MF module-info.class org/ org/fenixedu/ org/fenixedu/foo/ org/fenixedu/foo/alpha/ org/fenixedu/foo/alpha/Alpha.class org/fenixedu/foo/alpha/AlphaFactory.class org/fenixedu/foo/alpha/AlphaService.class org/fenixedu/foo/beta/ org/fenixedu/foo/beta/Beta.class org/fenixedu/foo/beta/BetaFactory.class org/fenixedu/foo/beta/BetaService.class org/fenixedu/foo/internal/ org/fenixedu/foo/internal/GreekUtil.class

Jigsaw - Create a module # --print-module-descriptor > jar -f mlib/foo.jar -p Name: org.fenixedu.foo Requires: java.base [ MANDATED ] Exports: org.fenixedu.foo.alpha org.fenixedu.foo.beta Conceals: org.fenixedu.foo.internal # listing jar files > jar tvf mlib/foo.jar META-INF/ META-INF/MANIFEST.MF module-info.class org/ org/fenixedu/ org/fenixedu/foo/ org/fenixedu/foo/alpha/ org/fenixedu/foo/alpha/Alpha.class org/fenixedu/foo/alpha/AlphaFactory.class org/fenixedu/foo/alpha/AlphaService.class org/fenixedu/foo/beta/ org/fenixedu/foo/beta/Beta.class org/fenixedu/foo/beta/BetaFactory.class org/fenixedu/foo/beta/BetaService.class org/fenixedu/foo/internal/ org/fenixedu/foo/internal/GreekUtil.class

// org/fenixedu/bar/gamma/Gamma.java package org.fenixedu.bar.gamma; import org.fenixedu.foo.alpha.Alpha; public class Gamma { public static void main(String...args) { Alpha alpha = new Alpha(); System.out.println( "I am gamma!" ); } } org.fenixedu.bar.gamma.Gamma org.fenixedu.bar.gamma.GammaFactory org.fenixedu.bar.gamma.GammaService org.fenixedu.bar.internal.GreekUtil fenixedu-bar.jar Jigsaw - Module Dependency

Jigsaw - Module Dependency org.fenixedu.foo.alpha.Alpha org.fenixedu.foo.alpha.AlphaFactory org.fenixedu.foo.alpha.AlphaService org.fenixedu.foo.beta.Beta org.fenixedu.foo.beta.BetaFactory org.fenixedu.foo.beta.BetaService org.fenixedu.foo.internal.GreekUtil fenixedu-foo.jar org.fenixedu.bar.gamma.Gamma org.fenixedu.bar.gamma.GammaFactory org.fenixedu.bar.gamma.GammaService org.fenixedu.bar.internal.GreekUtil fenixedu-bar.jar Gamma imports Alpha

Jigsaw - Module Dependency ├── module-info.java └── org └── fenixedu └── bar ├── gamma │ ├── Gamma.java │ ├── GammaFactory.java │ └── GammaService.java └── internal └── GreekUtil.java org.fenixedu.bar.gamma.Gamma org.fenixedu.bar.gamma.GammaFactory org.fenixedu.bar.gamma.GammaService org.fenixedu.bar.internal.GreekUtil fenixedu-bar.jar // module-info.java module org.fenixedu.bar { // requires java.base; requires org.fenixedu.foo; }

Jigsaw - Running a module > javac -modulepath mods/ -d mods/org.fenixedu.bar $(find org.fenixedu.bar/src -name '*.java') > jar --create --file mlib/bar.jar --main-class org.fenixedu.bar.gamma.Gamma -C mods/org.fenixedu.bar . > jar -f mlib/bar.jar -p Name: org.fenixedu.bar Requires: org.fenixedu.foo java.base [ MANDATED ] Main class: org.fenixedu.bar.gamma.Gamma Conceals: org.fenixedu.bar.gamma org.fenixedu.bar.internal > java -mp mlib -m org.fenixedu.bar I am gamma!

Jigsaw - Module dependencies > jdeps -s mlib/bar.jar mlib/foo.jar bar.jar -> mlib/foo.jar bar.jar -> java.base foo.jar -> java.base

Jigsaw - Module dependencies > jdeps -dotoutput . mlib/bar.jar mlib/foo.jar

Jigsaw - Modular Runtime Images (JEP 200) ● Create a custom jdk image with only the necessary modules > jlink --modulepath $JDKMODS:mlib --addmods org.fenixedu.bar --output myimage > myimage/bin/java -listmods [email protected] org.fenixedu.bar org.fenixedu.foo

Application Migration

Typical Application JDK JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR JAR

Sample Application JDK jackson- annotations.jar jackson- databind.jar jackson-core.jar bar.jar foo.jar

Migration Strategies

Top Down

Sample Application JDK jackson- annotations.jar jackson- databind.jar jackson-core.jar bar.jar foo.jar

Sample Application module java.base jackson-core.jar jackson- databind.jar jackson- annotations.jar module bar module foo module java.logging module java.sql module java.xml

Automatic Modules “Real” modules Module name based on JAR file name (with some dark wizardry) Simply move the non-modular JARs from the classpath to the modulepath Exports all packages Requires all modules on the modulepath

Sample Application // src/bar/module-info.java module org.fenixedu.bar { requires org.fenixedu.foo; }

Sample Application // src/bar/module-info.java module org.fenixedu.bar { requires org.fenixedu.foo; ?? requires jackson-core.jar ?? ?? requires jackson-databind.jar ?? }

Sample Application // src/bar/module-info.java module org.fenixedu.bar { requires org.fenixedu.foo; requires jackson.core; requires jackson.databind; }

Automatic Modules module java.base module jackson.core module jackson.databind module jackson.annotations module bar module foo module java.logging module java.sql module java.xml

Bottom Up or ‘How to migrate your library’

Bottom Up Migration JDK jackson- annotations.jar jackson- databind.jar jackson-core.jar bar.jar foo.jar

Bottom Up Migration module java.base bar.jar foo.jar module java.logging module java.sql module java.xml module jackson.core module jackson.databind module jackson.annotations

Bottom Up Migration $ java -mp mlib -cp lib/foo.jar:lib/bar.jar -addmods jackson.databind org. fenixedu.bar.gamma.Gamma Exception in thread "main" java.lang.reflect. InaccessibleObjectException: Unable to make member of class org.fenixedu.bar.gamma.Gamma accessible: module jackson.databind does not read

Unnamed Module All non-modular JARs in the classpath are added to the ‘Unnamed Module’ Reads all other modules in the application Exports all its packages Real modules are not allowed to explicitly depend on the unnamed module Read-node may be added in runtime via reflection

Unnamed Module package java.lang.reflect; public final class Module { public String getName(); public boolean canRead(Module source); public Module addReads(Module source); ... }

Unnamed Module Module source = clazz.getModule(); this.getClass().getModule().addReads(source);

Go forth and modularize! Download the Jigsaw Early-Access build http://openjdk.java.net/projects/jigsaw/ea Try out this presentation code https://github.com/sergiofbsilva/jigsaw

Links http://openjdk.java.net/projects/jigsaw/ http://openjdk.java.net/projects/jigsaw/talks/ http://mail.openjdk.java.net/mailman/listinfo/jigsaw-dev http://openjdk.java.net/projects/jdk9/

Thank you!