Head toward Java 14 and Java 15
•
1 gefällt mir•676 views
Slide for Tech Talk #21 Java 14 and JJUG CCC 2020 Spring (aborted)
Empfohlen
Empfohlen
Weitere ähnliche Inhalte
Was ist angesagt?
Was ist angesagt? (20)
Ähnlich wie Head toward Java 14 and Java 15
Ähnlich wie Head toward Java 14 and Java 15 (20)
Mehr von Yuji Kubota
Mehr von Yuji Kubota (20)
Kürzlich hochgeladen
Kürzlich hochgeladen (20)
Head toward Java 14 and Java 15
- 4. Disclaimer I'vetestedthecontentsofthisdocumentbyJDK14.0.1andJDK15 (build22)whichareavailableon jdk.java.net asmuchaspossible, butnotallofthemhavebeentested,sopleasedoanoperation confirmationbeforeyouattempttomodifyyourcode. IconfirmedtheJDKimplementationby hg.openjdk.java.net/jdk- updates/jdk14u and jdk/jdk . 4
- 9. 358:HelpfulNullPointerExceptions $ java Sample Exception in thread "main" java.lang.NullPointerException at Sample.main(Sample.java:4) 9
- 10. 4: String name = person.getName().toUpperCase(); public class Sample { public static void main(String... args){ Person person = new Person(); String name = person.getName().toUpperCase(); } static class Person { String name = null; Person() { } String getName() { return name; } } } 10
- 11. 4: String name = person[i][j][k] // <= Nullable * 4 .getPersonalInformation() // <= Nullable .getName() // <= Nullable .getFamilyName() // <= Nullable .toUpperCase(); // <= Nullable 11
- 12. -XX:+ShowCodeDetailsInExceptionMessages $ java -XX:+ShowCodeDetailsInExceptionMessages Sample Exception in thread "main" java.lang.NullPointerException: Cann at Sample.main(Sample.java:4) Exception in thread "main" java.lang.NullPointerException: Cannot invoke "String.toUpperCase()" // When because the return value of "Sample$Person.getName()" is null // What 12
- 13. Case:localvariable 3: String[] names = null; 4: names[1].toLowerCase(); $ java -XX:+ShowCodeDetailsInExceptionMessages LocalStringArray Exception in thread "main" java.lang.NullPointerException: Cannot load from object array // When because "<local1>" is null // What at LocalStringArray.main(LocalStringArray.java:4) $ javac -g LocalStringArray.java // Add all debugging information $ java -XX:+ShowCodeDetailsInExceptionMessages LocalStringArray Exception in thread "main" java.lang.NullPointerException: Cannot load from object array // When because "names" is null // What at LocalStringArray.main(LocalStringArray.java:4) 13
- 17. 363:RemovetheConcurrentMarkSweep(CMS)Garbage Collector Goodbye -XX:+UseConcMarkSweepGC Ifyousetaboveoption,JVMwilllaunchwithDefaultGC YoushouldspecifyGCalgorthimclearly OpenJDK 64-Bit Server VM warning: Ignoring option UseConcMarkSweepGC; support was removed in 14.0 17
- 19. 366:DeprecatetheParallelScavenge+SerialOldGC Combination -XX:+UseParallelGC -XX:-UseParallelOldGC 19
- 20. ToolsandAPIs 20
- 21. 349:JFREventStreaming CollecteventsfromlocalJavaprocess import java.time.Duration; import jdk.jfr.consumer.RecordingStream; public class JFRSample { public static void main(String... args) { try (RecordingStream rs = new RecordingStream()) { // Enable events JVM will collect periodically rs.enable("jdk.CPULoad") .withPeriod(Duration.ofSeconds(10)); // Registers consumer to perform on event matching a name rs.onEvent("jdk.CPULoad", System.out::println); // Nothing happens when you specify an uncollected event rs.onEvent("jdk.SafepointCleanup", System.out::println); rs.start(); } } } 21
- 22. $ java Sample jdk.CPULoad { startTime = 18:30:06.225 jvmUser = 1.96% jvmSystem = 0.10% machineTotal = 16.56% } jdk.CPULoad { startTime = 18:30:07.239 jvmUser = 0.26% jvmSystem = 0.03% machineTotal = 16.60% } : 22
- 24. Useconfigurationinsteadofenablingeventsbyyourself import jdk.jfr.Configuration; import jdk.jfr.consumer.EventStream; import jdk.jfr.consumer.RecordingStream; public class JFRSample { public static void main(String... args) throws Exception { try (RecordingStream rs = new RecordingStream( // Set "default" or "profile" Configuration.getConfiguration("default"))) { // Can register action on events JVM collects by "default" rs.onEvent("jdk.CPULoad", System.out::println); rs.start(); } } } 24
- 25. CollecteventsfromremoteJavaprocessviaRepository # Launch jshell with enabling JFR $ jshell -J-XX:StartFlightRecording=maxage=15m,settings=default Started recording 1. : # Check repository path of targeted Java process (jshell) $ jcmd $(pgrep jshell) JFR.configure 14006: Current configuration: Repository path: /private/var/folders/wm/dz3pkjf11hb1mph16365hj1h0000gp/T/2020_ : -XX:FlightRecorderOptions=repository=/path/to 25
- 26. Openstreamwithrepositorypath import java.io.IOException; import java.nio.file.Path; import jdk.jfr.consumer.EventStream; public class JFRRemoteSample { public static void main(String... args) throws IOException { // Pass repository path via argument try (EventStream es = EventStream .openRepository(Path.of(args[0]))) { // Method Profiling Sample event es.onEvent("jdk.ExecutionSample", System.out::println); es.start(); } } } $ java JFRRemoteSample /private/(snip)/2020_05_14_18_57_15_15902 jdk.ExecutionSample { startTime = 19:09:55.345 sampledThread = "JFR Periodic Tasks" (javaThreadId = 13) state = "STATE_RUNNABLE" stackTrace = [ jdk.jfr.internal.PlatformRecorder.periodicTask() line: 474 jdk.jfr.internal.PlatformRecorder.lambda$startDiskMonitor$1() line: 417 jdk.jfr.internal.PlatformRecorder$$Lambda$52.1546693040.run() java.lang.Thread.run() line: 832 ] } 26
- 29. Basicusage $ jpackage --name sample --input <directory_includes_jar> --main-jar sample.jar --main-class Sample $ ls sample-* sample-1.0.dmg Withcustomruntimeimage: # Show ependent modules $ jdeps -summary Sample.class Sample.class -> java.base Sample.class -> java.desktop # Create runtime image that consists only of dependent modules $ jlink --add-modules java.base,java.desktop --output image # Create installer with custom runtime image $ jpackage --name sample --input <directory_includes_jar> --main-jar sample.jar --main-class Sample --runtime-image image 29
- 30. 352:Non‑VolatileMappedByteBuffers New jdk.nio.mapmode.ExtendedMapMode wasadded FileChannel channel = FileChannel.open(NON_VOLATITLE_PATH); // If READ only, use `READ_ONLY_SYNC` instead channel.map(ExtendedMapMode.READ_WRITE_SYNC, 0, bufferSize); 30
- 31. 370:Foreign‑MemoryAccessAPI(Incubator) non‑heap allocateDirect :upto2G( Integer.MAX_VALUE )perobject JavaNativeInterface:managememorybyyourself Unsafe.allocateMemory() :potentialremovewithoutwarning VarHandle intHandle = MemoryHandles.varHandle(int.class); try (MemorySegment segment = MemorySegment.allocateNative(100)) { MemoryAddress base = segment.baseAddress(); for (int i = 0 ; i < 25 ; i++) { intHandle.set(base.offset(i * 4), i); } } 31
- 33. 371:HiddenClasses Protectdynamicclassesagainstunpredictableaccess cannotfindbybytecodelinkageand Class::forName , Classloader::loadClass Normalclasses ClassLoader::defineClass Hiddenclasses MethodHandles.Lookup#defineHiddenClass(byte[] bytes, boolean initialize, MethodHandles.Lookup.ClassOption... options) byteから隠されたクラスを生成し、reflectiveaccessをも つlookupオブジェクトを返す このlookupオブジェクトが隠しクラスのClassオブジェク トを取得する唯一の方法 33