Classpath - compile time

Classpath - runtime

Scale Down

Deprecated JDK modules

• …​ back to Java EE

Non-standard JDK modules

• Deleted classes
• Hidden packages

Non-standard JDK modules

• Internal modules

Module descriptor

Build module

Run module

Multi-modules layout

Create module

The Jigsaw Sandwich

The Jigsaw Sandwich

Create module

Split package

Regular export

Restricted export

sun.misc.Unsafe

Deep reflection

Deep reflection

• Open a package

• Open all the packages of the module

Transitive dependency

Transitive dependency

Static dependency

• Compile time only

Plain old jar

Plain old jar

• No dependency to classpath

Plain old jar

Automatic Module

• Plain old jar in module-path

Automatic Module

Mixed mode

Mixed mode

Big kill switch

Command line java / javac

• Add root module

• --add-modules

Command line java / javac

jdeps

• Diagnostic tool
  • since Java 8

• jdeps --jdk-internals

jlink

• Custom runtime image

• Specific for a platform

• For small devices or in the cloud

jlink

Minimal VM

• size of the classical VM: 20 megs
• size of the minimal VM: 3 megs

Ahead Of Time compilation

• Module ⇒ shared library
  • .so, .dll, .dynlib

Ahead Of Time compilation

• Run in AOT mode

Benchmarks

Benchmarks

Jigsaw Goals

• Reliable configuration
  • No classpath anymore
  • compile time / runtime fidelity

Jigsaw Goals

• Scale down the platform
  • downsized unit of re-use

Jigsaw Goals

• Strong encapsulation
  • Separate public types from implementation
  • Enhanced security

Jigsaw Goals

• Closed World
  • Ahead of time optimizations

Jigsaw Goals