A reasonable overview of Java 9 [Devoxx PL`2017]

The upcoming Java 9 release brings with it modularity, a new REPL, a new default garbage collector, HTTP 2 client, and much more. However, project Jigsaw requires so much of developer's attention that it's hard to see the true value of the upcoming release.

In this session we'll look at the features of Java 9 that developers not architects will face the most: welcome additions to the API: Optional, Date and Time, Stack walker, process management, collection literals (just kidding, they are factories of course), performance improvements, where to find the Unsafe and how to treat it after all. Is JShell a real tool or a toy to run fun one-liners?

Should you rush to migrate to Java 9, as you did with the Java 8 and those sweet lambdas? Are multi-release jars nice or a point of pain?

In this session we'll try to answer whether it is all worth it and how could you proceed with it.

Transcript

1. JAVA 9
   A REASONABLE OVERVIEW
   Oleg Šelajev
   ZeroTurnaround
   @shelajev
   

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2. @shelajev
   

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4. WHAT’S JAVA 9 CODE NAME?
   

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6. Safe harbour and
   stuff
   wARNING!!
   Sarcasm ahead!
   

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7. September 21st
   

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14. IDE SUPPORT
    

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15. http://0t.ee/rebellabs-survey-2017
    

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16. http://openjdk.java.net/projects/jigsaw/
    JEP 200: The Modular JDK
    JEP 220: Modular Run-Time Images
    JEP 260: Encapsulate Most Internal APIs
    JEP 261: Module System
    JEP 282: jlink: The Java Linker
    JSR 376: JAVA PLATFORM MODULE SYSTEM
    

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20. AREN’T MODULES EXCITING?
    

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21. module org.shelajev.N {
    requires com.google.guava;
    requires transitive com.shelajev.api;
    requires static compile.time.dependency;
    requires transitive static and.its.dependencies;
    exports public.classes.in.these.packages;
    exports some.packages to specific.modules;
    opens packages.for.reflection.and.public;
    opens these.packages to specific.modules, and.others;
    uses some.service.api;
    provides some.api with some.implementation;
    }
    

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22. MECHANISM COMPILE ACCESS REFLECTION ACCESS
    export all code > public all code > public
    qualified export specified modules > public specified modules > public
    open package none all code > private
    qualified open package none specified modules > private
    open module none all code > private
    https://blog.codefx.org/java/reflection-vs-encapsulation/
    

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23. --add-exports /=
    --add-exports java.management/sun.management=ALL-UNNAMED
    --add-modules=java.xml.bind
    COMMAND LINE FUN
    

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26. WHAT’S DOES
    method.isAccessible()
    RETURN?
    

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28. AUTOMATIC MODULES
    Any JAR on the module path without a
    module descriptor is an automatic module.
    Automatic modules implicitly export all their packages
    and read all other modules.
    

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29. --module-path --classpath
    Modular JAR application module unnamed module
    Non-Modular JAR automatic module unnamed module
    

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30. --ILLEGAL-ACCESS=PERMIT
    1 WARNING, OTHERWISE LIKE CLASSPATH
    

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31. MIGRATION STRATEGY
    

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32. LET’S TALK ABOUT MAVEN
    

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34. PETCLINIC APP
    [ERROR] Failed to execute goal org.apache.maven.plugins:maven-jar-plugin:2.6:jar (default-jar) on project spring-
    petclinic: Execution default-jar of goal org.apache.maven.plugins:maven-jar-plugin:2.6:jar failed: An API
    incompatibility was encountered while executing org.apache.maven.plugins:maven-jar-plugin:2.6:jar:
    java.lang.ExceptionInInitializerError: null
    

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35. Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make protected final java.lang.Class
    java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain) throws
    java.lang.ClassFormatError accessible:
    module java.base does not "opens java.lang" to unnamed module @4b9e00f3
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:337) ~[na:na]
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:281) ~[na:na]
    at java.base/java.lang.reflect.Method.checkCanSetAccessible(Method.java:198) ~[na:na]
    at java.base/java.lang.reflect.Method.setAccessible(Method.java:192) ~[na:na]
    at org.springframework.cglib.core.ReflectUtils$1.run(ReflectUtils.java:54) ~[na:na]
    at java.base/java.security.AccessController.doPrivileged(Native Method) ~[na:na]
    at org.springframework.cglib.core.ReflectUtils.(ReflectUtils.java:44) ~[na:na]
    ... 38 common frames omitted
    PETCLINIC APP
    built on Java 8, running Java 9
    

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36. PETCLINIC APP
    built on Java 8, running Java 9
    with --permit-illegal-access
    Caused by: java.lang.ClassNotFoundException: javax.xml.bind.JAXBException
    at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:466) ~[na:na]
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:553) ~[na:na]
    at org.springframework.boot.loader.LaunchedURLClassLoader.loadClass(LaunchedURLClassLoader.java:94)
    ~[spring-petclinic-1.5.1.jar:1.5.1]
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:486) ~[na:na]
    ... 34 common frames omitted
    

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37. PETCLINIC APP
    built on Java 8, running Java 9
    with --permit-illegal-access
    and --add-modules java.se.ee
    

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39. Multirelease JARs
    

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40. G1GC
    GC
    

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41. Generational GC
    

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42. G1GC
    

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43. @shipilev
    https://shipilev.net/jvm-anatomy-park/3-gc-design-and-pauses/
    

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44. https://2017.geekout.ee/videos/#day2-02
    

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45. mad skillz, amirite?
    

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46. JSON
    picture of a hipster
    

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47. import jdk.incubator.http.HttpClient;
    import jdk.incubator.http.HttpResponse;
    HttpClient.newHttpClient().send(
    newBuilder(URI.create("https://www.google.com"))
    .GET()
    .build(),
    HttpResponse.BodyHandler.asString())
    .body();
    http2
    

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48. STRING PERFORMANCE
    JEP 254: Compact Strings
    Adopt a more space-efficient internal representation for strings.
    JEP 280: Indify String Concatenation
    Change the static String-concatenation bytecode sequence
    generated by javac to use invokedynamic calls to JDK library
    functions.
    

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50. THINGS NOT TO TOUCH
    UNLESS YOU’RE 100% SURE
    multi-release jars
    jlink
    

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51. THINGS NOT TO TOUCH
    UNLESS YOU’RE 100% SURE
    multi-release jars
    jlink
    Unsafe
    

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52. Java 9, the cooking guide
    1. Upgrade your IDE, your other tools
    2. Upgrade Spring to 5.0
    3. Add --illegal-access=warn
    a. fix easily fixable warnings
    4. Wait 365 days (or more) on the classpath
    

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55. oleg@zeroturnaround.com
    @shelajev
    Find me and chat with me!
    

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