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![Specification versus implementation Many ways to implement a Java virtual machine specification compliant. This is more obvious for Java EE where different application containers are explicitly branded as such. Sun HotSpot Appeal VM JRockit Apache Harmony Java compatibility kit (JCK) - not open-sourced JVMS? JVMS? JVMS? GPL + CP exception commercial Apache license public static void main(String[] args) { System.out.println("Hello world!"); } OCTLA: free if made available under the GPL, no change within namespace, heavily OpenJDK- derived, Oracle-approved](https://image.slidesharecdn.com/stateofthejavaecosystem-191107190216/75/Java-and-OpenJDK-disecting-the-ecosystem-6-2048.jpg)
![Project preview: Panama. jdk.java.net/panama foreign function interface data layouts jextract -t nvidia -L /usr/lib -lnvidia-ml --record-library-path /opt/cuda/targets/x86_64-linux/include/nvml.h -o nvidia.jar import java.foreign.*; import java.foreign.memory.*; import java.lang.invoke.MethodHandles; import nvidia.nvml_h; import nvidia.nvml_lib; public class Sample { public static void main(String[] args) { Libraries.loadLibrary(MethodHandles.lookup(), "nvidia-ml"); try(Scope s = nvml_lib.scope().fork()) { nvml_lib.nvmlInit_v2(); } } } Look into JNA for a currently available solution without direct JVM-support.](https://image.slidesharecdn.com/stateofthejavaecosystem-191107190216/75/Java-and-OpenJDK-disecting-the-ecosystem-26-2048.jpg)
![Project review and preview: Amber. Collection of language extensions: Local variable type inference (Java 10) Switch expressions (Java 12, Java 13, preview) Pattern matching for instanceof Records Enhanced enums (on hold) var value = "Hello World!"; Function<String, String> f = (@NonNull var arg) -> arg;Function<String, String> f = arg -> arg;Function<String, String> f = (var arg) -> arg; int result = switch (input) { case "foo" -> 1; case "bar" -> 2; default -> 3; } int result; switch (input) { case "foo": result = 1; break; case "bar": result = 2; break; default: result = 3; } "twonlinesn"""" two lines """ Object o = fetch(); if (o instanceof String s) { String result = s; } String text = String.format("%s: %d", new Object[] {"foo", new Integer(42)}); String text = String.format("%s: %d", "foo", 42); Local-variable syntax for lambda parameters (Java 11) Text blocks (Java 13, preview) Java Compiler intrinsics API Sealed types Lambda leftovers (on hold) String text = (invokedynamic) DynamicFormat::format, "%s: %d", "foo", 42; sealed interface Base permits Foo, Bar { } record Foo(String bar) { }](https://image.slidesharecdn.com/stateofthejavaecosystem-191107190216/75/Java-and-OpenJDK-disecting-the-ecosystem-28-2048.jpg)
![Project overview: Graal. java -XX:+UnlockExperimentalVMOptions -XX:+UseJVMCICompiler -Djvmci.Compiler=graal MyApp jaotc -output MyApp.so MyApp.class java -XX:AOTLibrary=./libMyApp.so MyApp native-image -cp myapp.jar MyApp interface JVMCICompiler { CompilationRequestResult compileMethod(CompilationRequest request); } import org.graalvm.polyglot.Context; class GraalJavaScript { public static void main(String[] args) { try (Context context = Context.newBuilder().allowNativeAccess(true).build()) { System.out.println(context.eval("js", "14 + 2")); } } }](https://image.slidesharecdn.com/stateofthejavaecosystem-191107190216/75/Java-and-OpenJDK-disecting-the-ecosystem-29-2048.jpg)
Uploaded byRafael Winterhalter
Java and OpenJDK: disecting the ecosystem
This document provides a comprehensive overview of the Java ecosystem, covering topics such as the Java Language Specification, Java Virtual Machine, improvements and features from various JEPs (Java Enhancement Proposals), and the role of the Java Community Process. It discusses OpenJDK projects and distributions, company involvement, and outlines important licensing and release cadence considerations. Additionally, the document touches on various project previews like Loom, Panama, Valhalla, and Amber, which aim to extend the capabilities of the Java language.
Java and OpenJDK: disecting the ecosystem
- 1. An inventory of theJava ecosystem
- 2. What do Iwant to accomplish with this talk? Software consultant at day, open source developer at night.
- 3. What is Javaanyways? JLS JVMSJava Language Specification Java Virtual Machine Specification 51 character sequences, formed from ASCII letters, are reserved for use as keywords and cannot be used as identifiers (§3.8). Class and interface names that appear in class file structures are always represented in a fully qualified form known as binary names (JLS §13.1). Such names are always represented as CONSTANT_Utf8_info structures (§4.4.7) and thus may be drawn, where not further constrained, from the entire Unicode codespace. Language Preview Specifications + One specification per major release, no changes in update releases: https://docs.oracle.com/javase/specs/ 1. Introduction 11. Exceptions 2. Grammar 12. Execution 3. Lexical structure 13. Binary compatibility 4. Types, values, variables 14. Blocks, statements 5. Conversions, contexts 15. Expressions 6. Names 16. Definite assignment 7. Packages, modules 17. Threads, locks 8. Classes 18. Type inference 9. Interfaces 19. Syntax 10. Arrays 1. Introduction 2. JVM structure 3. Compilation 4. Class file format 5. Loading, linking, initialization 6. JVM instruction set 7. Opcode mnemonics
- 4. JEPJava Enhancement Proposal JSRJavaSpecification Request Java Language Specification Java Virtual Machine Specification JCKJava Compatibility Kit TCKsSpecification Test Kits The Java Community Process (JCP). Java Servlet Specification Java Message Specification Java RESTful Web Services (JAX-RS) ... ECExecutive Committee 2020: Alibaba, ARM, Azul, BNY Mellon, Credit Suisse, Eclipse Foundation, Fujitsu, Goldman Sachs, JetBrains, Hazelcast, Hewlett Packard, IBM, Intel, London Java Community, MicroDoc, Oracle, SAP, Software AG, SouJava, Tomitribe, Twitter, V2COM OpenJDK Community TCK and EA TCK License Agreement (OCTLA) spec lead and expert group Jakarta Servlet Specification Jakarta Message Specification Jakarta RESTful Web Services (JAX-RS) ... Jakarta EE Working Group Jakarta EE Steering Committee
- 5. The Java CommunityProcess (JCP) by example: The Java platform module system (JPMS) JEP JEP 261: Module system JEP 200: The Modular JDK JEP 201: Modular Source Code JEP 220: Modular Runtime Images JEP 162: Prepare for Modularization JEP 179: Document JDK API Support and Stability JEP 281: jlink – The Java Linker JEP 275: Modular Java Application Packaging JEP 260: Encapsulate Most Internal APIs JSR RI JSR 376: Java Platform Module System Maling lists: jpms-spec-experts jpms-spec-observers jpms-spec-comments Voting process: 12.2014 JSR Review 11.2015 JSR Renewal 04.2017 Review 06.2017 Review Reconsideration 08.2017 Final Approval OpenJDK OpenJDK project: Jigsaw Maling lists: jigsaw-dev Project sponsor: Compiler Group EA build: jdk.java.net Specification diffs: JLS, JVMTS, JAR, JNI, JVMTI, JDWP
- 6. Specification versus implementation Manyways to implement a Java virtual machine specification compliant. This is more obvious for Java EE where different application containers are explicitly branded as such. Sun HotSpot Appeal VM JRockit Apache Harmony Java compatibility kit (JCK) - not open-sourced JVMS? JVMS? JVMS? GPL + CP exception commercial Apache license public static void main(String[] args) { System.out.println("Hello world!"); } OCTLA: free if made available under the GPL, no change within namespace, heavily OpenJDK- derived, Oracle-approved
- 7. OpenJDK: a projectto implement a reference of the specification for common use jdk jdk*u hg.openjdk.java.net mirror.vendor.com jdk.java.net (Java 14 EA) adoptopenjdk.net (Java 8 - 13) OpenJDK Vulnerability Group (OJVG) aws.amazon.com/corretto azul.com bell-sw.com developers.redhat.com/products/openjdk sap.github.io/SapMachine oracle.com/technetwork/java/javase Oracle contributor agreement (OCA): shared copyright with Oracle jdk.java.net (Java 13, 6 months)
- 8. The OpenJDK project:governance model. Group Project Participant Contributor OpenJDK Member OpenJDK Lead JDK Release Project Group Lead Group MemberAuthor Committer Reviewer Project Lead Chair 2x At-Large Member Vice-Chair x Observer openjdk.java.net/census
- 9. The OpenJDK project:proposing and applying a patch. Request for Enhancement (RFE) Request for Comments (RFC) Request for Review (RFR) patch hg diff (inline) webrev Sponsor jtreg JCK Merge Compatibility and Specification Review (CSR) Backport 1. Remember tooling. 4. Remember JVMTI 2. Remember JNI 5. Remember JPDA. 3. Remember reflection API. 6. Remember serialization.
- 10. The OpenJDK project:backporting and update projects. hg.openjdk.java.net jdk/jdk jdk-updates/jdk13u jdk/jdk13 jdk-updates/jdk12u jdk/jdk12 jdk-updates/jdk11u jdk/jdk11 jdk-updates/jdk11u-dev jdk-updates/jdk10u jdk/jdk10 jdk10/jdk10 jdk-updates/jdk9u jdk9/jdk9 jdk8/jdk8u jdk8/jdk8 jdk8/jdk8u-dev jdk7/jdk7u jdk7/jdk7 jdk7/jdk7u-dev jdk6/jdk6 September 2018
- 11. The OpenJDK project:clone, build and test DIY. sudo apt install mercurial ./build/linux-x86_64-server-release/jdk/bin/java --fullversion hg clone https://hg.openjdk.java.net/jdk/jdk cd jdk sudo apt install build-essential bash configure --with-boot-jdk=~/jdk-13 make images hg clone https://hg.openjdk.java.net/code-tools/jtreg sh jtreg/make/build-all.sh ~/jdk-8 bash configure --with-boot-jdk=~/jdk-13 --disable-warnings-as-errors openjdk full version "14-internal+0-adhoc.rafael.jdk" export JT_HOME=~/jtreg/build/images/jtreg bash configure --with-boot-jdk=~/jdk-13 --disable-warnings-as-errors make test-tier1
- 12. In what waydo OpenJDK builds differ? jdk jdk*u hg.openjdk.java.net hotspot java.base jdk.compiler jdk jdk*u OpenJ9 openj9 java.base jdk.compiler jdk jdk*u Azul Zing hotspot java.base jdk.compiler hotspot/gc/c4 hotspot/jit/falcon hotspot/readynow JDK JRE-compact1 JRE (with JavaFX)JRE multiple binaries possible
- 13. What are themore common OpenJDK distributions? ZULUZING Oracle OpenJDK
- 14. Other VMs thatoffer subset functionality. DAVLIK ART CE EE Substrate Does not support all standard APIs, e.g. java.awt, java.swing, java.beans, java.instrumentation. Does not support Java byte code at runtime (Dalvik: dex format, ART: native). JCK-approved VM unless compiled via native-image extension (Substrate VM): - Requires setup to use reflection. - JVMTI and security manager not supported. - Dynamic byte code not supported. - Method handles and invokedynamic (unless via lambda meta factory) not supported.
- 15. Name Runtime JITGC Versions Platforms Free Support JCK AdoptOpenJDK HotSpot C1/C2 G1, SR, PL, ZGC, SH* 8 - 13 Linux, Mac, Win Yes Yes No AdoptOpenJDK OpenJ9 OpenJ9 Openj9 8 - 13 Linux, Mac, Win Yes Yes No Oracle OpenJDK HotSpot C1/C2 G1, SR, PL, ZGC 13, 14-EA, EA Linux, Mac, Win* Yes No Yes Oracle JDK HotSpot C1/C2 G1, SR, PL, ZGC 8, 11, 13 Linux, Mac, Win No Yes Yes Azul Zing HotSpot C1/Falcon C4 8, 11 Linux No Yes Yes Azul Zulu HotSpot C1/C2 G1, SR, PL, ZGC, SH* 6 - 13 Linux, Mac, Win Yes Yes Yes Red Hat OpenJDK HotSpot C1/C2 G1, SR, PL, ZGC, SH 8, 11, 13 RHE Linux, Win Yes Yes Yes SAP Machine HotSpot C1/C2 G1, SR, PL, ZGC, SH* 11, 13 Linux, Mac, Win Yes No Yes Corretto HotSpot C1/C2 G1, SR, PL, ZGC 8, 11 Linux, Mac, Win Yes On AWS Yes Liberica HotSpot C1/C2 G1, SR, PL, ZGC, SH* 8, 11, 13 Linux, Mac, Win Yes Yes Yes Dragonwell HotSpot C1/C2 G1, SR, PL 8 Linux Yes No Yes Pivotal Spring RT HotSpot C1/C2 G1, SR, PL 7 - 12 Linux Yes Yes No Graal VM HotSpot C1/Graal G1, SR, PL 8 Linux, Mac, Win* Both Yes Yes Substrate VM None Graal GenScavenge 8 Linux, Mac, Win* Both Yes No Android ART ART ART 7 (subset 8) Android Yes No No Debian HotSpot C1/C2 G1, SR, PL, ZGC, SH* 8 - 13 Linux Yes No No Note: ZGC supported since Java 11. Deprecated CMS not mentioned. Shenandoah (SH) marked with a star available since Java 12. SR = serial, PL = parallel. Only subset of platforms.
- 16. Java is stillfree (dah!). java -XX:+UnlockCommercialFeatures MyApp java MyApp Oracle OpenJDK java -XX:+UnlockCommercialFeatures MyApp java MyApp java MyApp Java 8u202 (January 2019) Java 8u211 (April 2019) java -XX:+UnlockCommercialFeatures MyApp Java 8u40 (March 2015) Java 13.0.1 (October 2019), updates until March 2020 Old versions: No license change! Free unless commercial options are enabled in production environments.
- 17. Release cadence: OracleOpenJDK vs Oracle JDK. Sep '17 Mar '18 Sep '18 Mar '19 Sep '19 Mar '20 Sep '20 Mar '21 Java 9 Java 10 Java 11 Java 12 Java 13 Java 14 Java 15 Java 8 (until March 2022, extended: March 2025) Java 11 (until March 2023, extended March 2026) Java 8 Java 12 Java 13 Java 14 Java 15
- 18. Release cadence: RedHat OpenJDK and others. Sep '17 Mar '18 Sep '18 Mar '19 Sep '19 Mar '20 Sep '20 Mar '21 Java 8 (until June 2023) Java 11 (until October 2024) Java 8 Java 11 Java 7 (until June 2020)
- 19. Release cadence: AzulZulu. Sep '17 Mar '18 Sep '18 Mar '19 Sep '19 Mar '20 Sep '20 Mar '21 Java 6 (until December 2021) Java 13 (March 2023) Java 7 (until July 2023) Java 8 (until March 2026) Java 11 (until September 2027) Java 15 (March 2023) Java 6 (until 2019)
- 20. How involved arecompanies in the OpenJDK? Sources: https://blogs.oracle.com/java-platform-group/building-jdk-11-together https://blogs.oracle.com/java-platform-group/the-arrival-of-java-13
- 21. Software license families. publicdomain permissive strong copyleft restrictive trade secret 2/3-clause BSD MIT Apache 4-clause BSD GPL LGPL AGPL BCL GPL + CPE dual licensed ? EPL weak copyleft
- 22. Adoption strategy: bleedingedge versus LTS. Java 8 (bytecode 52) Java 11 (bytecode 55) module-info.class encapsulation of reflective access built-in class loader implementation change platform class loader replaces extension mechanism new URL schema for class file resources new version string format reduction of preconfigured modules (in Java 9) Java 13 (bytecode 57) Enhanced deprecation (since Java 10) sun.misc.Unsafe::defineClass removed (in Java 12) Java 14-EA (bytecode 58) -net.bytebuddy.experimental=true Java 14+X (bytecode 58+X) invokedynamic (Java 7) nestmates (Java 11) constantdynamic (Java 11) java.bytecode.* (?) Most changes are performance improvements or feature extensions! Update your libraries, don't "hack" and you should be fine.
- 23. Migrating from JavaEE to Jakarta EE. jakarta.servlet.* jakarta.ws.rs.* ... javax.servlet.* javax.ws.rs.* ... javax.sql.* javax.management.* ... public class LegacyServletBridge implements jakarta.servlet.Servlet { private final javax.servlet.Servlet delegate; public LegacyServlet(javax.servlet.Servlet delegate) { this.delegate = delegate; } @Override public void service(jakarta.servlet.ServletRequest req, jakarta.servlet.ServletResponse resp) { delegate.service(new LegacyServletRequest(req), new LegacyServletResponse(resp)); } } org.hibernate.validation.* javax.validation.*
- 24. The Java developer(advocacy) community. developer advocacy developer "recognition" developer awards meetups and developer conferences
- 25. Project preview: Loom. publicclass SampleServlet extends HttpServlet { private final HttpClient client; public SampleServlet(HttpClient client) { this.client = client; } @Override protected void doGet( HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException { resp.getOutputStream().write(client.fetchResponse()); } } public class SampleServlet extends HttpServlet { private final HttpClient client; public SampleServlet(HttpClient client) { this.client = client; } @Override protected void doGet( HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException { AsyncContext context = req.startAsync(); client.fetchResponseAsync().onComplete(response -> { context.getResponse().getOutputStream().write(response); context.complete(); }); } } run doGet fetchResponse OS-backed-thread doGet fetchResponse doGet fetchResponse suspend runrun jdk.java.net/loom fibers/continuations tail-call optimization
- 26. Project preview: Panama. jdk.java.net/panama foreignfunction interface data layouts jextract -t nvidia -L /usr/lib -lnvidia-ml --record-library-path /opt/cuda/targets/x86_64-linux/include/nvml.h -o nvidia.jar import java.foreign.*; import java.foreign.memory.*; import java.lang.invoke.MethodHandles; import nvidia.nvml_h; import nvidia.nvml_lib; public class Sample { public static void main(String[] args) { Libraries.loadLibrary(MethodHandles.lookup(), "nvidia-ml"); try(Scope s = nvml_lib.scope().fork()) { nvml_lib.nvmlInit_v2(); } } } Look into JNA for a currently available solution without direct JVM-support.
- 27. Project preview: Valhalla. a b c classNonPrimitiveSample { Integer a, b, c; } Integer 42 class PrimitiveSample { int a, b, c; } a = 42 b = 84 c = 1 object object Integer 84 object object Integer 1 object object new PrimitiveSample() new NonPrimitiveSample() jdk.java.net/valhalla inline types generic specialization cache lines: stales processor inline class
- 28. Project review andpreview: Amber. Collection of language extensions: Local variable type inference (Java 10) Switch expressions (Java 12, Java 13, preview) Pattern matching for instanceof Records Enhanced enums (on hold) var value = "Hello World!"; Function<String, String> f = (@NonNull var arg) -> arg;Function<String, String> f = arg -> arg;Function<String, String> f = (var arg) -> arg; int result = switch (input) { case "foo" -> 1; case "bar" -> 2; default -> 3; } int result; switch (input) { case "foo": result = 1; break; case "bar": result = 2; break; default: result = 3; } "twonlinesn"""" two lines """ Object o = fetch(); if (o instanceof String s) { String result = s; } String text = String.format("%s: %d", new Object[] {"foo", new Integer(42)}); String text = String.format("%s: %d", "foo", 42); Local-variable syntax for lambda parameters (Java 11) Text blocks (Java 13, preview) Java Compiler intrinsics API Sealed types Lambda leftovers (on hold) String text = (invokedynamic) DynamicFormat::format, "%s: %d", "foo", 42; sealed interface Base permits Foo, Bar { } record Foo(String bar) { }
- 29. Project overview: Graal. java-XX:+UnlockExperimentalVMOptions -XX:+UseJVMCICompiler -Djvmci.Compiler=graal MyApp jaotc -output MyApp.so MyApp.class java -XX:AOTLibrary=./libMyApp.so MyApp native-image -cp myapp.jar MyApp interface JVMCICompiler { CompilationRequestResult compileMethod(CompilationRequest request); } import org.graalvm.polyglot.Context; class GraalJavaScript { public static void main(String[] args) { try (Context context = Context.newBuilder().allowNativeAccess(true).build()) { System.out.println(context.eval("js", "14 + 2")); } } }
- 30.