What to expect from Java 9?

Ivan Krylov Azul Systems

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3Ivan Aivazovsky, 1850, The Ninth Wave, Russian Museum, St. Petersburg

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• Zing: A better JVM for the enterprise• Azul’s enterprise JVM focused on better metrics• Consistent performance - not just fast, always fast• Eliminate GC as a concern for enterprise apps• Very wide operating range

• From human-sensitive app responsiveness to low-latency trading

• From microservices to huge in-memory apps• Eliminates an entire class of engineering workarounds common in

Java•Zulu Embedded: When you need embedded Support

• 100% open source, based on OpenJDK• Certified Java SE compliant and compatible• Verified “non-contaminating” open source license• Identical metrics to OpenJDK and Oracle Java SE• World-class support offerings• Support for Linux & Windows; x86, ARM32, ARM64, PPC32,

MIPS4

Java 9 -Why talking about it now?

• Release scheduled for 2017

• Lots of breaking changes

• I am from Azul Systems - maker of compliant JDKs

• Observing the process from aside, unbiased view on changes

• Not promoting nor diminishing

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• Reflection is disallowed from operating on non-exported types, even with the use of setAccessible

• Jigsaw has only limited support for the dynamic introduction and alteration of modules

• Restrictions that make interoperability with alternative modular systems difficult.

• Source: http://wildfly.org/news/2016/12/12/Jigsaws-Missing-Pieces

Java 9 - concerns

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http://wiki.netbeans.org/InternalAPIsUnavailableInJava9

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“There are only two kinds of languages: the ones people complain about and the ones nobody uses.”

Bjarne Stroustrup

Java Timeline

JDK 6Dec 2006

JDK 7July 2011

JDK 8March 2014

JDK 9exp. July 2017

JDK 6Nov 2012

JDK 7Apr

2015

JDK 8exp. July 2018

J2SE 1.4 Dec 2006

JDK 5Oct 2009

9

GA

EOL

Java EOL & You?EOL datepassed

Security vulnerabilities

keep appearing&

Sign Support contact

Adopt OpenJDK (Zulu, IcedTea,

homebrew builds)Updated to latest

JDK

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Updates needed

What (was) new in Java 8• Lambdas • Method references• Type annotations • Repeated annotations • Interface a.k.a. default

methods

• Stream API• Date Time API• PermGen replacement (vendor

specific)• Nashorn, JavaScript Engine• New tools (jdeps,jjs,..)

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http://www.oracle.com/technetwork/java/javase/8-whats-new-2157071.html

How new features become part of Java standard?

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JEP process

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Source: http://cr.openjdk.java.net/~mr/jep/jep-2.0-02.html

JSR

Source: https://groups.google.com/forum/#!topic/java-social/InafCPMLLaA14

New APIs and features in Java 9

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Fabric methods for collectionsInstantiation of the immutable containers

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Set<String> set = new HashSet<>(); set.add("a"); set.add("b"); set = Collections.unmodifiableSet(set);

Set<String> set = Collections.unmodifiableSet( new HashSet<>(Arrays.asList("a", "b")));

Set<String> set = Collections.unmodifiableSet( new HashSet<String>() {{ add("a"); add("b"); }});

Set<String> set = Collections.unmodifiableSet( Stream.of("a", “b").collect(toSet()));

Set<String> set = Set.of("a", "b");

Fabric methods for collections

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• Set.of(a, b);

• List.of(a, b);

• Map.of(k1, v1);

• Map.of(k1, v1, k2, v2);

• Map.of(k1, v1, k2, v2, k3, v3);

• Map.ofEntries(entry(k1, v1), entry(k2, v2), ….. entry (kn, vn));

Stream API changes

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• Stream::takeWhile

• A replacement for the while (predicate_on_stream_element) { <keep processing this ordered stream>};

• Stream::dropWhile

• Some but start processing stream after the predicate

Stream API changes

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• Stream::takeWhile

• A replacement for the while (predicate_on_stream_element) { <keep processing this ordered stream>};

• Stream::dropWhile

• Some but start processing stream after the predicate

• Iterator with a predicate

• Stream::ofNullable

• Factory for a single non-null element

Syntax changes - Milling Project Coin• Private default methods

interface I { void a() { /*Common code*/ ; /*a’s specific code*/ } void b() { /*Common code*/ ; /*b’s specific code*/ } ?? - void c() { /*Common code*/ ; } }

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interface II { private void foo_private(String s); // Error: private method must declare body. private abstract void foo_abstract(int i, int j); // Error: private & abstract: bad combo void foo_decl(int x); // OK. private I foo_with_body() { return null; } // OK. }

interface I { void a() { с(); /*a’s specific code*/ } void b() { с(); /*b’s specific code*/ } private void c() { /*Common code*/ ; } }

Syntax changes - Milling Project Coin

• Effectively-final variables in try-with-resources expressions

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public static void main(String... args) throws …{ FileReader f = new FileReader(“test.txt”); br =new BufferedReader(fr); try (br) { // do something } catch (Exception ex) { } }

public static void main(String... args) throws …{ FileReader f = new FileReader(“test.txt"); try (br =new BufferedReader(fr)) { // do something } catch (Exception ex) { } }

Syntax changes - Milling Project Coin• @SafeVarargs in private methods

• (In Java 8 it was only final and static)

class VarargsFinalOnly { @SafeVarargs private void m(List<String>... args) { }}

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public class TypeInferrenceTest { Map<String, String> map = new HashMap<String, String>() { { map.put("key", "value"); } }; }

• Using diamond with anonymous classes when actual type may be deduced

public class TypeInferrenceTest { Map<String, String> map = new HashMap<> () { { map.put("key", "value"); } }; }

Syntax changes - Milling Project Coin

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Prior to Java 9./TypeInferrenceTest.java:7: error: cannot infer type arguments for HashMap<K,V> new HashMap<>() ^ reason: cannot use '<>' with anonymous inner classes where K,V are type-variables: K extends Object declared in class HashMap V extends Object declared in class HashMap 1 error

http://c2.com/cgi/wiki?DoubleBraceInitialization

Syntax changes - Milling Project Coin• Can’t use single _ as a name

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// key: compiler.warn.underscore.as.identifier // options: -source 8 -Xlint:-options

class UnderscoreAsIdentifierWarning { String _ = null;}

Process API Updates• JEP 102: Process API Updates

• What’s new:

• Get pid for this JVM

• Get list of processes

• Operations on trees of processes

Source: http://blog.takipi.com/java-9-the-ultimate-feature-list/ 24

Process proc = Runtime.getRuntime() .exec(new String[]{"/bin/sh", "-c", "echo $PPID"}); if (proc.waitFor()==0) { InputStream in = proc.getInputStream(); int available = in.available(); byte[] outputBytes = new byte[available]; in.read(outputBytes); String pid = new String(outputBytes); System.out.println("Your pid is " + pid) }

System.out.println("Your pid is " + ProcessHandle.current().getPid());

Spin Loop Hint (JEP-285)

• Scope: latency (& performance) • Features:

• New method j.l.Thread.onSpinWait()• On x86 - translates into the ‘pause’ instruction

• Already used 9 times in JSR 166 for JDK9• java/util/concurrent/locks/StampedLock.java• java/util/concurrent/Phaser.java• java/util/concurrent/SynchronousQueue.java

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Spin Loop Hint (JEP-285)

• Scope: latency (& performance) • Features:

• New method j.l.Thread.onSpinWait()• On x86 - translates into the ‘pause’ instruction

• Already used 9 times in JSR 166 for JDK9• java/util/concurrent/locks/StampedLock.java• java/util/concurrent/Phaser.java• java/util/concurrent/SynchronousQueue.java

class EventHandler { volatile boolean eventNotificationNotReceived; void waitForEventAndHandleIt() { while ( eventNotificationNotReceived ) { java.lang.Thread.onSpinWait(); } readAndProcessEvent(); } void readAndProcessEvent() { // Read event from some source and process it . . . }}

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Producer/Consumer and SLH

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Spin Loop Hint• Cool. I have spin loops. Wait for 9?

• May be not

• Just include the agrona library

• or look at java/org/agrona/hints/ThreadHints.java

• Works for older JDKs

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https://github.com/real-logic/Agrona/blob/master/src/main/java/org/agrona/hints/ThreadHints.java

JShell• Project Kulla http://openjdk.java.net/projects/kulla/

• In main trunk since JDK 9 EA build 90

• REPL as you know it for other languages

• Helps teaching Java class HelloWorld { public static void main(String[] args) { System.out.println(" "); } }

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Jshell Demo

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just kick ./bin/jshell and try yourself

Garbage First is on by default• Pros

• State-of-the-art GC in HotSpot (albeit being 14+ years old)

• Regional parallel concurrent collector

• Targeting both low pause and high throughput

• Default => Great number of users => Bugs detecter sooner => G1 will become even more robust shortly

• Cons

• Due to different characteristics it may reveal synchronisation problems in the code

• In recent years many bugs with Cassandra, Elasticsearch, Lucene were fixed in both GC and libraries. Perhaps, other ones are yet not discovered?

• source (dated July 2015): https://groups.google.com/forum/#!topic/mechanical-sympathy/JxsuVtIIOaY

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Surviving the change of default GC• If you used no i.e. default GC settings

• capture the ergonomics at your deployment sites

• consider explicitly setting GC flags in all deployment scripts

• If you already had selected and tuned GC flags

• No changes, old collectors not phasing out

• In any case - keep trying G1

• Understand how GC works

• Basic algorithms and associated metrics

• More reading: http://www.infoq.com/minibooks/java-garbage-collection31

New JEPs briefly. Performance• 193: Variable Handles

• 143: Improve Contended Locking

• 266: More Concurrency Updates

• 197: Segmented Code Cache

• 165: Compiler Control

• 243: Java-Level JVM Compiler Interface

• 246: Leverage CPU Instructions for GHASH and RSA

• 250: Store Interned Strings in CDS Archives

• 254: Compact Strings

• 280: Indify String Concatenation

• 230: Microbenchmark Suite

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Unified JVM Logging• For better diagnostics, uniform across all components• 6 levels of logging x dozens of tags • Output to stdout / stderr / file / rotating file • No more badly interleaved lines• -Xlog:help• 11 decorators

-Xlog:classinit -Xlog:classloaderdata -Xlog:defaultmethods -Xlog:itables -Xlog:monitormismatch -Xlog:safepoint -Xlog:startuptime -Xlog:vmoperation -Xlog:vtables -Xlog:verification

-XX:+TraceClassInitialization -XX:+TraceClassLoaderData -XX:+TraceDefaultMethods -XX:+TraceItables -XX:+TraceMonitorMismatch -XX:+TraceSafepoint -XX:+TraceStartupTime -XX:+TraceVMOperation -XX:+PrintVtables -XX:+VerboseVerification

java -Xlog:help

HTTP/2 today

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HTTP -> TCP

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• HTTP 0.9: The One-Line Protocol (1989)

• HTTP/1.0 (1996)

• HTTP/1.1: Internet Standard (1997)

• Keep alive; chunk encodings; byte-range requests, additional caching mechanisms, transfer encodings, and request pipelining

• HTTP/2.0 (since 2012)

Ref: https://hpbn.co/brief-history-of-http/

36https://speakerdeck.com/vietj/2-2

HTTP/2. Multiplexing

Stack walking API• Before 9: Throwable::getStackTrace и Thread::getStackTrace

StackTraceElement[] stack = Thread.currentThread().getStackTrace();

• Since 9 also possible to:

StackFrame[] stack =new StackWalker().walk((s) -> s.collect(Collectors.toArray()));

• New StackWalker class

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JEP 223: New Version-String Scheme• System Property Existing Proposed • ------------------------------- ------------ -------- • Early Access • java.version 1.9.0-ea 9-ea • java.runtime.version 1.9.0-ea-b73 9-ea+73 • java.vm.version 1.9.0-ea-b73 9-ea+73 • java.specification.version 1.9 9 • java.vm.specification.version 1.9 9

• Major (GA) • java.version 1.9.0 9 • java.runtime.version 1.9.0-b100 9+100 • java.vm.version 1.9.0-b100 9+100 • java.specification.version 1.9 9 • java.vm.specification.version 1.9 9

• Minor #1 (GA) • java.version 1.9.0_20 9.1.2 • java.runtime.version 1.9.0_20-b62 9.1.2+62 • java.vm.version 1.9.0_20-b62 9.1.2+62 • java.specification.version 1.9 9 • java.vm.specification.version 1.9 9

• Security #1 (GA) • java.version 1.9.0_5 9.0.1 • java.runtime.version 1.9.0_5-b20 9.0.1+20 • java.vm.version 1.9.0_5-b20 9.0.1+20 • java.specification.version 1.9 9

New JEPs briefly. Client/graphics• 258: HarfBuzz Font-Layout Engine

• 263: HiDPI Graphics on Windows and Linux

• 265: Marlin Graphics Renderer

• 262: TIFF Image I/O

• 257: Update JavaFX/Media to Newer Version of GStreamer (1.4.4)

• 251: Multi-Resolution Images

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New JEPs briefly. Security

• 219: Datagram Transport Layer Security (DTLS)

• 229: Create PKCS12 Keystores by Default

• 244: TLS Application-Layer Protocol Negotiation Extension

• 249: OCSP Stapling for TLS

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Unicode in Java 9

• 227: Unicode 7.0…

• … & 267: Unicode 8.0

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Modules

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Modules

Packages

Classes

fields & methods

Interfaces

…

Abstract Classes

…

Code encapsulation

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Problems being addressed• Java Runtime keeps getting bigger and bigger

• Java 8 profiles 1, 2, 3 provide partial solutions

• Jar / Classpath Hell

• What depends on what ..

• Optional dependancies, transitive dependancies

• Lazy class loading and initialization -> NoClassDefFoundError

• For code that escapes packages the visibility mechanism is poor - only public

• Classes from different packages “see” each other, even from different class loaders

• SecurityManager helps to protect, but it is not on by default44

Wikepedia оn Jar-hell

• Accidental presence of two different versions of a library installed on a system. This will not be considered an error by the system. Rather, the system will load classes from one or the other library. Adding the new library to the list of available libraries instead of replacing it may result in the application still behaving as though the old library is in use, which it may well be.

• Multiple libraries or applications require different versions of library foo. If versions of library foo use the same class names, there is no way to load the versions of library foo with the same classloader.

• The most complex JAR hell problems arise in circumstances that take advantage of the full complexity of the classloading system. A Java program is not required to use only a single "flat" classloader, but instead may be composed of several (potentially very many) nested, cooperating classloaders. Classes loaded by different classloaders may interact in complex ways not fully comprehended by a developer, leading to errors or bugs that are difficult to analyze, explain, and resolve.

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Jigsaw

JEP 162: Prepare for ModularizationJEP 200: The Modular JDKJEP 220: Modular Run-Time ImagesJEP 201: Modular Source CodeJEP 260: Encapsulate Most Internal APIsJEP 282: jlink: The Java Linker

JSR 376: Java Platform Module SystemJEP 261: Module System

ModularityJava Module

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Examples

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• 01 - Classpath hell

• 02 - The simplest example with Modules

• 03 - jimage

• 04 - Error “2 modules export the same package into module 3”

• 05 - Working with 2 “identical” classes in different modules

Example 1

src/com.azul.modules.module1/module-info.java

module com.azul.modules.module1 { exports com.azul.testpackage1; }

src/com.azul.modules.module2/module-info.java

module com.azul.modules.module2 {

requires com.azul.modules.module1;

}

com.azul.modules.module1/com/azul/testpackage1/A.java

package com.azul.testpackage1;public class B { public static void m() { System.out.println("-- I am in path1.com.azul.test.B.m() "); }}

com.azul.modules.module2/com/azul/testpackage2/A.java

package com.azul.testpackage2;

public class A { public static void main(String[] args) { System.out.println("Calling from com.azul.modules.module2.com.azul.testpackage2.A.main() "); com.azul.testpackage1.B.m(); }}

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New params javac/java (1)• # Compile

• >javac --module-source-path src -d target $(find com.azul.modules.module1 -name “*.java”)

• >javac --module-path mlib -d target/com.azul.modules.module2 $(find com.azul.modules.module2 -name “*.java”)# Run

• >java -p target -m mlib/com.azul.modules.module2

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New parameters for javac/java (2)

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• # Packaging

• jar --create --file=mlib/module2.jar --main-class=com.azul.testpackage2.A -C target/com.azul.modules.module2 .

• # Run

• $j/bin/java -p target -m com.azul.modules.module2

Reference: http://openjdk.java.net/projects/jigsaw/quick-start

Example 2./nashorn/src/jdk.scripting.nashorn/share/classes/module-info.java

module jdk.scripting.nashorn { requires java.logging; requires public java.scripting;

uses jdk.internal.dynalink.linker.GuardingDynamicLinker; uses jdk.nashorn.internal.runtime.CodeStore; provides javax.script.ScriptEngineFactory with jdk.nashorn.api.scripting.NashornScriptEngineFactory;

exports jdk.nashorn.api.scripting; exports jdk.nashorn.api.tree;

exports jdk.nashorn.internal.runtime to jdk.scripting.nashorn.shell; exports jdk.nashorn.internal.objects to jdk.scripting.nashorn.shell; exports jdk.nashorn.tools to jdk.scripting.nashorn.shell; }

META-INF/services

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Types of modules• Named

• Those containing module-info.class

• Automatic

• jar files placed to the module path

• Unnamed

• Contains all types in the classpath

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Can modularised & non-modularised code co-exist?

• Whatever is in classpath - going into unnamed modules

• Unnamed modules can access all named modules (requires *) /See next slide for a special note/

• The reverse isn’t true - must specify requires unnamed or …

• jar file in --module-path is being automatically converted to a module with a name matching the name of the jar file

• Therefore referred as automodules

• Provide transition path to jigsaw modules design

• Unnamed modules are being searched for types as a last option 53

Unnamed modules can access all named modules

• Not so true since JDK9 build 118• These modules are not accessible from unnamed modules: java.activation - java.annotations.common - java.corbajava.transaction - java.xml.bind - java.xml.ws

• One can still add visibility with a flag like `-addmods java.corba`

• Source: May 17th letter from Alan Bateman: http://mail.openjdk.java.net/pipermail/jdk9-dev/2016-May/004309.html

• More info: http://openjdk.java.net/jeps/26154

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jdeps -genmoduleinfo

cat /Users/ivan/test/modules/generated/glassfish.corba.omgapi/module-info.java module glassfish.corba.omgapi { requires public java.corba; requires public java.desktop; requires public java.rmi; exports com.sun.corba.ee.org.omg.CORBA; exports javax.rmi.CORBA; exports org.omg.CORBA; exports org.omg.CORBA.DynAnyPackage; exports org.omg.CORBA.ORBPackage; exports org.omg.CORBA.TSIdentificationPackage; exports org.omg.CORBA.TypeCodePackage; exports org.omg.CORBA.portable; exports org.omg.CORBA_2_3; exports org.omg.CORBA_2_3.portable; exports org.omg.CosNaming; exports org.omg.CosNaming.NamingContextExtPackage; exports org.omg.CosNaming.NamingContextPackage; exports org.omg.CosTSInteroperation; exports org.omg.CosTSPortability; exports org.omg.CosTransactions; exports org.omg.Dynamic; exports org.omg.DynamicAny; exports org.omg.DynamicAny.DynAnyFactoryPackage; exports org.omg.DynamicAny.DynAnyPackage; exports org.omg.IOP; exports org.omg.IOP.CodecFactoryPackage; exports org.omg.IOP.CodecPackage; exports org.omg.Messaging; exports org.omg.PortableInterceptor; exports org.omg.PortableInterceptor.ORBInitInfoPackage; exports org.omg.PortableServer; exports org.omg.PortableServer.CurrentPackage; exports org.omg.PortableServer.POAManagerPackage; exports org.omg.PortableServer.POAPackage; exports org.omg.SendingContext; exports org.omg.stub.java.rmi; }

jdeps

-genmoduleinfo

~/test/modules/generated/ glassfish-4.1.1/glassfish/modules/glassfish-corba-omgapi.jar

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jdeps -jdkinternalsglassfish-corba-orb.jar -> java.corba com.sun.corba.ee.impl.copyobject.OldReflectObjectCopierImpl (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.copyobject.OldReflectObjectCopierImpl$1 (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.encoding.BufferManagerWriteStream (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.IIOPInputStream (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.IIOPInputStream$1 (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.IIOPOutputStream (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.IIOPOutputStream$1 (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.ObjectStreamClass (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.ObjectStreamClass$1 (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.ObjectStreamField (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.io.ObjectStreamField$1 (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.presentation.rmi.JNDIStateFactoryImpl$1 (glassfish-corba-orb.jar) -> com.sun.jndi.cosnaming.CNCtx JDK internal API (java.corba) com.sun.corba.ee.impl.util.JDKClassLoader (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba) com.sun.corba.ee.impl.util.JDKClassLoader$1 (glassfish-corba-orb.jar) -> sun.corba.Bridge JDK internal API (java.corba)

jdeps

-jdkinternals

glassfish/ modules/ glassfish-corba-orb.jar

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java --add-exportsjava --add-exports :java.base/sun.security.provider=ALL-UNNAMED, java.base/sun.security.pkcs=ALL-UNNAMED, java.base/sun.security.util=ALL-UNNAMED, java.base/sun.security.x509=ALL-UNNAMED, :

java --add-readsjava --add-reads:java.management=testng

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• Consider an app with extensions

• The extension might require a different version of a module than loaded before

• The extension might require service providers

• Layer of modules encapsulates

• a module graph

• mapping from each module in that graph to a class loader

• Boot layer - created by VM at start time and suitable for most apps

• App can create a new layer - new universe of modules

• Stackable - package resolution starts with the app layer and goes down to the boot layer

Layers

Modularity

Source: http://openjdk.java.net/projects/jigsaw/doc/jdk-modularization.htmlJDK 7 b65

59http://cr.openjdk.java.net/~mr/jigsaw/ea/module-summary.html

Modularity

Source: http://openjdk.java.net/projects/jigsaw/doc/jdk-modularization.html

JDK 8 b48

60http://cr.openjdk.java.net/~mr/jigsaw/ea/module-summary.html

Modularity

Source: http://openjdk.java.net/projects/jigsaw/doc/jdk-modularization.html

JDK9 b157

61http://cr.openjdk.java.net/~mr/jigsaw/ea/module-summary.html

Modularity

Source: http://openjdk.java.net/projects/jigsaw/doc/jdk-modularization.htmlJDK9 b15762http://cr.openjdk.java.net/~mr/jigsaw/ea/module-summary.html

Jigsaw - Unresolved issueshttp://openjdk.java.net/projects/jigsaw/spec/issues/

63

• Module declarations

• #ModuleNameSyntax · #ModuleNameCharacters ? · #CompileTimeDependences ✔ · #ModuleAnnotations ✔ · #ModuleDeprecation ✔ · #ExportAnnotation

• Module artifacts

• #MultiModuleExecutableJARs · #MultiModuleJARs · #ReifiedModuleGraphs · #ModuleNameInManifest · #AddExportsInManifest ✔

• Module descriptors

• #ClassFileModuleName ? · #ClassFileAccPublic ✔ · #ClassFileAccModule ? · #StandardModuleAttributes

• Module graphs

• #CyclicDependences · #MutableConfigurations · #LazyConfigurationAndInstantiation · #CustomizableAutomaticModuleNameMapping ✔

• Services

• #ServiceLoaderEnhancements ✔

• Reflection

• #ClassFilesAsResources ✔ · #ResourceEncapsulation ✔ · #ResourceExistenceAndSize · #ReflectiveAccessToNonExportedTypes ? · #AwkwardStrongEncapsulation ? · #ReflectionWithoutReadability ✔ · #ReadabilityAddedByLayerCreator ? · #IndirectQualifiedReflectiveAccess ?

• Class loaders

• #AvoidConcealedPackageConflicts · #PlatformClassLoader ✔ · #ClassLoaderNames ✔

• Versioning

• #StaticLayerConfiguration · #MultipleModuleVersions · #VersionsInModuleNames ✔ · #VersionedDependences ? · #VersionSyntax

• Layers

• #NonHierarchicalLayers ? · #DiscardableModules

• Tooling

• #BootstrapClassLoaderSearchInJVMTI ✔ · #ReflectiveAccessByInstrumentationAgents ✔

Jigsaw - Unresolved issueshttp://openjdk.java.net/projects/jigsaw/spec/issues/

• Module declarations

• #ModuleNameSyntax · #ModuleNameCharacters ? · #CompileTimeDependences ✔ · #ModuleAnnotations ✔ · #ModuleDeprecation ✔ · #ExportAnnotation

• Module artifacts

• #MultiModuleExecutableJARs · #MultiModuleJARs · #ReifiedModuleGraphs · #ModuleNameInManifest · #AddExportsInManifest ✔

• Module descriptors

• #ClassFileModuleName ? · #ClassFileAccPublic ✔ · #ClassFileAccModule ? · #StandardModuleAttributes

• Module graphs

• #CyclicDependences · #MutableConfigurations · #LazyConfigurationAndInstantiation · #CustomizableAutomaticModuleNameMapping ✔

• Services

• #ServiceLoaderEnhancements ✔

• Reflection

• #ClassFilesAsResources ✔ · #ResourceEncapsulation ✔ · #ResourceExistenceAndSize · #ReflectiveAccessToNonExportedTypes ? · #AwkwardStrongEncapsulation ? · #ReflectionWithoutReadability ✔ · #ReadabilityAddedByLayerCreator ? · #IndirectQualifiedReflectiveAccess ?

• Class loaders

• #AvoidConcealedPackageConflicts · #PlatformClassLoader ✔ · #ClassLoaderNames ✔

• Versioning

• #StaticLayerConfiguration · #MultipleModuleVersions · #VersionsInModuleNames ✔ · #VersionedDependences ? · #VersionSyntax

• Layers

• #NonHierarchicalLayers ? · #DiscardableModules

• Tooling

• #BootstrapClassLoaderSearchInJVMTI ✔ · #ReflectiveAccessByInstrumentationAgents ✔64

(My) takeaways on Java 9 modules• Purpose - explicit listing of dependancies

• Will provide new optimization paths

• Compatible with jar/cp

• OSGi compatibility and reflection are a concern

• Jigsaw - rough flight all way along, loosing features

• Lost ability to match versions 65

Jigsaw - links• If you google it - discard all posts before 2014, probably even before 2015 too

• State of Jigsaw (March 8 2015)

• http://openjdk.java.net/projects/jigsaw/spec/sotms/

• JavaOne 2016 (also Devoxx BE 2017)

• http://openjdk.java.net/projects/jigsaw/talks/#j1-2016

• Code was integrated in JDK9 EA build 111

• See also: http://blog.codefx.org/java/dev/features-project-jigsaw-java-9/

• http://blog.codefx.org/java/dev/javaone-2015-under-the-hood-of-project-jigsaw/66

is thiswhat wewanted?

(rhetorical)

67

Ivan Krylov www.azul.com Azul Systems ivan @azul.com

@JohnWings