Java 9/10/11 - What's new and why you should upgrade
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Java 11 is the new Java release and, differently from Java 9 and Java 10, it is a "Long Term Support" release - we will see what that means exactly. This presentation details the main new features of Java 11, starting from licensing (where there are important changes - in particular the Oracle JDK may only be used in production if you have a support contract with Oracle), to arrive to the new Java 11 features, with a quick peek back at what was introduced in Java 9 and Java 10. The main Java 11 arguments are: • Two new garbage collectors: EpsilonGC e ZGC • Support for TLS 1.3 • Possibility to execute a single source file • New HTTP client based on the Flow API • Removal of modules (CORBA, JTA, @Inject, ecc.) • Bytecode news (nest-mates, dynamic constants)
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Java 9/10/11 - What's new and why you should upgrade
- 1. sbordet@webtide.com Java 9/10/11 What’s new and why you should upgrade @simonebordet
- 2. sbordet@webtide.com Simone Bordet ● @simonebordet ● sbordet@webtide.com ● Java Champion ● Works @ Webtide ○ The company behind Jetty and CometD
- 3. sbordet@webtide.com Java 11 ● Java 11 is here! ● “Long Term Support” (LTS) Release ○ Java 8 was the previous LTS Release ○ Java 9 and Java 10 already unmaintained
- 4. sbordet@webtide.com Java 11 OpenJDK 11 Repository https://hg.openjdk.java.net Oracle JDK Binary https://java.oracle.com OpenJDK Binary http://jdk.java.net/11 RedHat JDK Binary Azul JDK Binary (Zulu) AdoptOpenJDK Binary https://adoptopenjdk.net
- 5. sbordet@webtide.com Java 11 ● What does LTS really mean? ● During the 6 months of “life” of a Java 11: ○ OpenJDK Binary -> GPL ○ AdoptOpenJDK -> GPL ○ Azul Zulu -> GPL ○ Oracle JDK Binary -> Oracle License ■ MUST PAY Oracle for production use
- 6. sbordet@webtide.com Java 11 ● After the 6 months of “life” of a Java 11: ○ Upgrade to Java 12 ○ Stay on Java 11
- 7. sbordet@webtide.com ● After 6 months, you stay on Java 11 ○ Never update -> exposed to vulnerabilities ○ Update Java 11 -> 11.0.x ● Community (RedHat) backports fixes ● Vendors create binary builds ○ AdoptOpenJDK -> GPL ○ Other vendors (Oracle, Azul, RedHat, …) -> PAY Java 11
- 9. sbordet@webtide.com Java 9 ● Java 9 introduced the Java Module System ● Along with it, a number of breaking changes ○ Upgrading from 8 to 9/10/11 is NOT simple ○ Many runtime behavior changes ○ Needs very thorough testing
- 10. sbordet@webtide.com Java 9 ● Removed tools.jar ○ Attach API, Compiler API, JavaDoc API, etc. ● Removed JavaDB ● Removed endorsed and extension directories ○ $JAVA_HOME/lib/endorsed ○ $JAVA_HOME/jre/lib/ext
- 11. sbordet@webtide.com Java 9 ● Class loading implementation changed ○ Different behavior to support modules ClassLoader sysCL = ClassLoader.getSystemClassLoader(); // Throws ClassCastException now! URLClassLoader urlCL = (URLClassLoader)sysCL;
- 12. sbordet@webtide.com Java 9 ● Loading resources URL resource = sysCL.getResource("java/lang/String.class"); // Not a file:/ nor a jar:/ URL! resource = jrt:/java.base/java/lang/String.class URL resource = sysCL.getResource("/com/foo/bar.properties"); // It’s there, but it won’t find it! resource = null;
- 13. sbordet@webtide.com Java 9 ● New version string scheme ○ 1.8.0_181 -> 9.0.1 ○ Broke many Maven Plugins, Jetty, etc. ● JDK 9’s java.lang.Runtime.Version class ○ Cannot parse JDK 8 version string ○ Must implement custom parsing to support both
- 14. sbordet@webtide.com Java 9 ● Internal APIs encapsulated ○ Cannot access sun.* or com.sun.* classes ● Finalization ○ sun.misc.Cleaner -> java.lang.ref.Cleaner ○ Object.finalize() -> deprecated ● Unsafe ○ Some sun.misc.Unsafe usage replaced by VarHandle
- 15. sbordet@webtide.com Java 9 ● Multi Release jars com/ acme/ A.class B.class META-INF/ versions/ 9/ com/ acme/ A.class <- Replaces normal A.class C.class
- 16. sbordet@webtide.com Java 9 ● Variable Handles ○ Expose some Unsafe functionality class ConcurrentLinkedQueue_BAD { // BAD, adds indirection AtomicReference<Node> head; }
- 17. sbordet@webtide.com Java 9 class ConcurrentLinkedQueue { private Node head; private static final VarHandle HEAD; static { HEAD = MethodHandles.lookup() .findVarHandle(ConcurrentLinkedQueue.class, "head", Node.class); } public void m() { if (HEAD.compareAndSet(...)) ... } } }
- 18. sbordet@webtide.com Java 9 ● Process APIs Process p = new ProcessBuilder() .command("java") .directory(new File("/tmp")) .redirectOutput(Redirect.DISCARD) .start(); ProcessHandle.of(p.pid()) .orElseThrow(IllegalStateException::new) .onExit() .thenAccept(h -> System.err.printf("%d exited%n", h.pid()) );
- 19. sbordet@webtide.com Java 9 ● Concurrent APIs Enhancements ○ java.util.concurrent.Flow ■ Identical APIs and semantic of ReactiveStreams ○ CompletableFuture enhancements ■ Common scheduler for timeout functionalities CompletableFuture.supplyAsync(() -> longJob()) .completeOnTimeout("N/A", 1, TimeUnit.SECONDS) CompletableFuture.supplyAsync(() -> longJob()) .orTimeout(1, TimeUnit.SECONDS)
- 20. sbordet@webtide.com Java 9 ● jshell - Read-Eval-Print-Loop (REPL) ● Pretty powerful! ○ AutoCompletion, Imports, Javadocs ○ History, search ○ Syncs with external editor ○ Function and forward references ○ ...
- 21. sbordet@webtide.com Java 9 ● G1 is the default Garbage Collector ● Much improved from 8 and even better in 11 ○ Adaptive start of concurrent mark ○ Made internal data structures more concurrent ○ More phases parallelized ○ Reduced contention ○ Reduced memory consumption
- 22. sbordet@webtide.com Java 9 ● Unified GC logging ○ Not compatible with previous GC logs ● Every GC logs differently ● Example ○ - Xlog:gc*,ergo*=trace,ref*=debug:file=log s/gc.log:time,level,tags
- 23. sbordet@webtide.com Java 9 ● JVM options changes ○ 50 options removed - JVM refuses to start ○ 18 options ignored - 12 options deprecated ● Must review your command line! ○ Especially if you had custom GC tuning options
- 25. sbordet@webtide.com Java 10 ● Local variable type inference (a.k.a. var) ○ http://openjdk.java.net/projects/amber/LVTIstyle.html // Infers ArrayList<String> var list = new ArrayList<String>(); // infers Stream<String> var stream = list.stream();
- 26. sbordet@webtide.com Java 10 ● var is not a keyword, it is a reserved type name ○ It’s a valid identifier, unless used in places where the compiler expects a type name int var = 13;
- 27. sbordet@webtide.com Java 10 ● Good var usage var message = "warning, too many features"; var anon = new Object() { int count = 0; } anon.count++; // Compiles!
- 28. sbordet@webtide.com Java 10 ● Controversial var usage // What type ? var result = processor.run(); // IDE cannot help you var list = new <ctrl+space>
- 29. sbordet@webtide.com Java 10 ● Experimental Graal JIT ○ https://www.graalvm.org/ ● -XX:+UnlockExperimentalVMOptions -XX: +UseJVMCICompiler ● Not yet recommended in production ○ Twitter uses it in production, you may too (YMMV)
- 30. sbordet@webtide.com Java 10 ● Docker awareness ○ On by default ○ https://blog.docker.com/2018/04/improved-docker-containe -XX:-UseContainerSupport -XX:ActiveProcessorCount=n -XX:MinRAMPercentage=p -XX:InitialRAMPercentage=p -XX:MaxRAMPercentage=p
- 32. sbordet@webtide.com Java 11 ● Two new Garbage Collectors ○ Epsilon GC ○ ZGC ● Epsilon GC ○ No-operation GC
- 33. sbordet@webtide.com ● ZGC ○ 5 years of closed source development @ Oracle ○ XX:+UnlockExperimentalVMOptions XX:+UseZGC ○ Single Generation, Region Based ○ Concurrent Marking ○ Concurrent Compaction ○ Very low STW pause times Java 11
- 34. sbordet@webtide.com Java 11 ● Removed methods ○ Thread.stop(Throwable) ○ Thread.destroy() ○ System.runFinalizersOnExit(boolean) ○ Some SecurityManager.check*() methods
- 35. sbordet@webtide.com Java 11 ● Removed modules ○ java.activation (JAF) ○ java.corba ○ java.transaction (JTA) ○ java.xml.bind (JAXB) ○ java.xml.ws (JAX-WS) ○ java.xml.ws.annotation (@PostConstruct, ...) ● Replaced by standalone jars ○ https://dzone.com/articles/apis-to-be-removed-from-java-11
- 36. sbordet@webtide.com Java 11 ● Java Flight Recorder ○ Open Sourced by Oracle, included in OpenJDK 11 ○ java -XX:StartFlightRecording ... ● Java Mission Control ○ Open Sourced by Oracle ○ Downloads at https://jdk.java.net/jmc/ ○ JMC 7 scheduled for January 2019
- 37. sbordet@webtide.com Java 11 ● TLS 1.3 ○ More secure and recent version of TLS ○ Removed vulnerable/weak ciphers ○ Added new ciphers and algorithms ● Using SSLEngine? Verify it works!
- 38. sbordet@webtide.com Java 11 ● Launch Single-File Source-Code programs $ java Hello.java ● Compiled in-memory with Graal ● Teaching ● Java Scripts
- 39. sbordet@webtide.com Java 11 ● HTTP client ○ Supports both HTTP/1.1 and HTTP/2 ○ Based on the j.u.c.Flow APIs HttpClient c = HttpClient.newBuilder().build(); HttpRequest r = HttpRequest.newBuilder() .uri(...).build(); CompletableFuture<String> f = c.sendAsync(r, BodyHandlers.ofString());
- 40. sbordet@webtide.com Java 11 ● Nest Mates ○ Inner (nested) classes introduced in Java 1.1 ○ Outer class can access inner class ■ Via compiler tricks - bridge methods java.lang.UnsupportedOperationException at NestExample.init(NestExample.java) at NestExample.access$000(NestExample.java) at NestExample$Inner.(NestExample.java) at NestExample.main(NestExample.java)
- 41. sbordet@webtide.com Java 11 ● Nest Mates ○ Now specified in the JVM Specification ○ New class file attribute ○ New reflection APIs: Class.getNestMembers(), ... ○ New JVM access controls at runtime ● Do you play with bytecode? ○ Use ASM 7+
- 43. sbordet@webtide.com Conclusions ● Upgrade from Java 8 takes time ○ Lots of runtime changes ● Java 8 will be soon unmaintained / unavailable ○ Skip Java 9 and Java 10 - go straight to Java 11 ● Lots of good stuff and more coming ○ And coming every 6 months now!