keraton / jigsaw-tuto

Code created during code code jigsaw session in Egencia

Java Modularity

Why module ?

• Export only what you want
  • Hide the implementation detail
• Java module, public in the same module
  • Compilation and runtime
  • Reflection
• Better encapsulation

Module structure

Using java convention src/{your module name }/{your module} Example :

src/com.greetings/com/greeting/Main.java

For the sake of simplicity we are going to use IntelliJ structure.

com.greetings/src/com/greeting/Main.java

The application

// Greeting apps

    GREETING APP -> Greeting Service        -> Greeting Bean
                 -> Greeting Reflection                     

Create monolith module

Define your module with module-info.java.

• Module name
• Module requirements

Create the greeting app module which only print Hello World. This is a monolith application which contains all the necessary code.

Separate App and Service

Define your module with module-info.java.

• Module exports

Use Bean and Repo instead of String

Define your module with module-info.java.

• Module requires transitive and non transitive

Use export to a friend instead of export all

Export Greeting Repo only to the Greeting Service.

Define your module with module-info.java.

• Module export friends

Use Greeting Reflection

Get internal value of Greeting Bean by using deep reflection.

Define your module with module-info.java.

• Open module or opens packages

Plugin Architecture

// Greeting apps

    GREETING APP -> Greeting Service Interface  -> Greeting Service Impl 1
                                                -> Greeting Service Impl 2 (optional)
                 

Define the Service Interface

Define your module with module-info.java.

• Declare interface with use
• Provide implementation
• Use implementation

Automatic module and unnamed module

TBD