Getting ready for java 9

About me

 

@arnaudroger

https://arnaudroger.github.io/blog/

 

 

 

http://simpleflatmapper.org/

https://github.com/arnaudroger/NoopFactory

 

 

About me

 

What do I know about java 9?

  • SimpleFlatMapper modularized since August 2016
  • wrote one article for site point
  • spend too much time following java 9 devs

 

 

Java 9

 

  • early-access available
  • http://jdk.java.net/9/
  • Still suggested to changes
    • last proposed change was on 5th of June
    • impact mainly integration of old jar as a module
  • apart from Jigsaw very stable

@arnaudroger https://arnaudroger.github.io/blog/

Java 8 EOL

 

 

see Oracle Java SE Support Roadmap

  • Three years after the general availability date (GA) of a major release
  • One year after the GA of a subsequent major release
  • Six months after a subsequent major release has been established as the default Java Runtime Environment (JRE) for end-user desktops on java.com

@arnaudroger https://arnaudroger.github.io/blog/

Schedule

 

 

 

 

@arnaudroger https://arnaudroger.github.io/blog/

Schedule

 

 

 

 

 

 

 

 

Schedule change

  • GA 31st September

@arnaudroger https://arnaudroger.github.io/blog/

Why the delay?

  • Blame Jigsaw JEP 200*
  • JSR 277 Early draft review was 11 Oct, 2006 targeting JDK 7

 

* JEP : JDK Enhancement Proposal

@arnaudroger https://arnaudroger.github.io/blog/

Let's talk about JPMS aka Jigsaw

 

 

 

 

Why? Why? Why?

What is all that module system about?

Why did it take more than 11 years to do?

@arnaudroger https://arnaudroger.github.io/blog/

Jigsaw why?

 

 

 

 

 

@arnaudroger https://arnaudroger.github.io/blog/

What's a module

 

It's mostly a jar

with a module-info.class

  • required modules
  • visible packages
  • services exported
  • services used

 

But no version information.

Only a module if on the module path.

module simpleflatmapper.converter {
        requires simpleflatmapper.util;
        exports org.simpleflatmapper.converter;
        
        uses org.simpleflatmapper.converter.ConverterFactoryProducer;
}

@arnaudroger https://arnaudroger.github.io/blog/

What's a module

  • Reflection restriction
    • setAccessible on private field
    • unless module is open
    • can --add-open on command line
  • Does not apply to classpath code

    • recent change, was dissallowed before

    • --illegal-access=permit is the default

-> old code breaking encapsulation will work,

for now. but security is compromised...

run with --illegal-access=deny if you can.

 

@arnaudroger https://arnaudroger.github.io/blog/

Why did it take so long?

  • Java SE code was ugly... non sense dependency chain
  • loads of rework to end up with :

 

 

@arnaudroger https://arnaudroger.github.io/blog/

Why is still being delayed

  • Migration concern
    • automatic module name
    • reflection access for non module
  • Meta module concern
    • no version
    • no cyclic dependencies
    • no access to internal module api

 

 

 

 

 

@arnaudroger https://arnaudroger.github.io/blog/

What to be concerned about

  • do you use jvm internal api sun.*
    • sun.misc.BASE64Decoder
  • you can find out with jdep

The following are still accessible

  • sun.misc.{Signal,SignalHandler}

  • sun.misc.Unsafe

  • sun.reflect.Reflection::getCallerClass(int)

  • sun.reflect.ReflectionFactory.newConstructorForSerialization

Same applies to your dependency.

 

 

Other  impactful changes

 

  • G1 becomes the default GC
    • different latency
    • different tuning strategies
  • String compaction
    • lower memory footprint
    • might incur higher cpu

 

 

 

@arnaudroger https://arnaudroger.github.io/blog/

Is Java9 just about pain?

 

91 JEPs

 

 

 

 

@arnaudroger https://arnaudroger.github.io/blog/

Compact String

JEP 254

 

  • NO API CHANGE
  • stored as byte[]
  • encoded as LATIN-1 or UTF-16
  • better jit/intrinsic to mitigate cost
  • some operation faster/some slower
  • disable latin-1 compression using -XX:-CompactStrings

 

@arnaudroger https://arnaudroger.github.io/blog/

JShell JEP 222

  • java REPL*
  • auto completion

 

 

 

* Read–eval–print loop

@arnaudroger https://arnaudroger.github.io/blog/

AOT

JEP 295

 

 

 

  • Ahead of time compilation
  • no profiling information
  • no supported yet

 

 

 

@arnaudroger https://arnaudroger.github.io/blog/

Spin-Wait Hint

JEP 285

 

  • Smallest JEP ever
  • java.lang.Thread.onSpinWait()
  • transformed into a PAUSE instruction on x86
  • useful for busy spin

 

 

 

@arnaudroger https://arnaudroger.github.io/blog/

Stack-Walking API

JEP 259

  • Faster than new Throwable()
  • Cost proportional to amount traversed
  • Access to getCallerClass
  • new Throwable() can be faster if
    • full traversal
    • access to debug info - line number.

 

more details https://www.sitepoint.com/deep-dive-into-java-9s-stack-walking-api/

@arnaudroger https://arnaudroger.github.io/blog/

Variable Handles

JEP 193

 

  • Partial safe unsafe replacement
  • No memory address
  • on fields and array elements
  • memory fences

  • Reachability fence

  • CAS

 

@arnaudroger https://arnaudroger.github.io/blog/

Javadoc search

JEP 225

http://download.java.net/java/jdk9/docs/api/index.html?overview-summary.html

@arnaudroger https://arnaudroger.github.io/blog/

Java next

  • use release train

ship what's ready at a specified date

  • Interesting work
    • Valhalla, value types
    • Panama, native code interaction
      • Intel vectorization API!!!

    • Shenandoah, ultra-low pause time garbage collector

    • Graal, JIT compiler, potential C2 replacement

@arnaudroger https://arnaudroger.github.io/blog/

Questions?

 

 

 

 

 

 

 

@arnaudroger https://arnaudroger.github.io/blog/

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