The document provides an overview of Java 9 modules, discussing their structure and features such as strong encapsulation and reliable configuration. It also covers how to create and package modules, along with compilation and runtime execution processes. Additional topics include transitive dependencies, linking, and various Java 9 module-related concepts and references.

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