Modularization is the act of decomposing a system into self contained modules. It possibly makes you think of component-based development.

1. By:
Harmeet Singh (Taara)
Software Consultant

2. Agenda
1. Before Java 9
2. Modules.
3. Java 9 Modules
4. Compilation, Packaging & Linking
5. Demo.
6. Leftover's

3. Before Java 9
➔Encapsulation
➔
private, protected or public

4. Before Java 9
➔Classpath

5. Modules
➔ Modularization is the act of decomposing a system into self
contained modules.
➔ It possibly makes you think of component-based
development

6. Java 9 Modules
- By using module
➔ Reliable Configuration ->
The system checks all dependencies before compiling
or running code.
➔ Strong Encapsulation ->
Modules explicitly choose what to expose to other
modules.
➔ Modular JDK/JRE

7. Java 9 Modules

8. Java 9 Modules

9. Java 9 Modules
- How to create modules
module com.dept {
exports com.dept.info
}
module com.account {
exports com.account.info;
}
module com.user {
requires com.dept;
requires com.account;
exports com.user.info;
}

10. Java 9 Modules
- Points to remember
➔ requires keyword indicates a dependency.
➔ exports keyword only export defined package to other modules.
➔ Modules name must be a unique.
➔ Module descriptor always start with module keyword.
➔ The implicit dependency java.base automatically added to a
module descriptor.
➔ Only explicitly exported packages can be access from other
modules
➔ Modules dependencies are not transitive.

11. Java 9 Modules
Q. How we achieve transitive dependency ???
module java.sql {
requires public java.logging;
requires public java.xml
}
Module com.knoldus {
requires java.sql;
}

12. Compilation/ Execution
➔ javac ­d <target­dir> <source­file> <module­file>
­ javac ­d target src/com.user/com/user/info/Launcher.java
src/com.user/module­info.java
➔ javac ­d <target­dir> ­­modules­source­path <all­source­
files>
­ javac ­d target ­­module­source­path src $(find ­name
"*.java")
➔ java –module­path <target­dir> ­­module <module­
name>/<full­package­name­main­class>
­ java ­p target ­m com.user/com.user.info.Launcher

13. Packaging
➔ jar ­­create –file=<target­dir­path> ­C <compiled­module­
path> <class­files­dir>
­ jar ­­create ­­file=libs/account­module.jar ­C
target/com.account .
➔ jar ­­create –file=<target­dir­path> ­­main­class=<full­
package­name­main­class> ­C <compiled­module­path> <class­
files­dir>
­ jar ­­create ­­file=libs/user­module.jar ­­main­
class=com.user.info.Launcher ­C target/com.user .
➔ java ­p libs ­m com.user

14. Linking
- Run Time Image
➔ What if, we required special distribution of the Java
Runtime containing the bare minimum to run our
application ???
➔ Jlink ­­module­path $JAVA_HOME/jmods:<compiled­
modules> ­­add­modules <module1>:<module2> ­­output
<image­name>
➔ jlink ­­module­path $JAVA_HOME/jmods:target ­­add­
modules com.user ­­output app
➔ bin/java <absolute­name­of­main­class>

15. Java 9 Module
DEMO

16. Leftovers
➔ Module Path
➔ Modules using Reflection
➔ Types of Modules
➔ Service Loader
➔ JMOD
➔ Java Shell
➔ Process API
➔ Reactive Streams

17. References:
✔ http://openjdk.java.net/projects/jigsaw/quick-start
✔ Java9 Modularity: Patternsand Practices
✔ https://blog.knoldus.com/2016/09/23/kick-off-java-9-project-jigsaw-part-i/
✔ Graph Theory for Geeksby Oliver Widder, CC-BY