Project Jigsaw introduces a modular system to Java to address issues with non-modular code. It divides the Java platform API into named modules that clearly define dependencies and exported packages. This avoids issues with classes from sun.* and com.sun.* packages being inaccessible or the huge size of rt.jar. The module system allows modular and non-modular code to coexist through automatic modules and the unnamed module. Tools like jdeps and jlink are provided to help with adoption and management of modules.

1. Moving to Module
Issues & Solutions
Project Jigsaw
Java in the Box
Yuichi Sakuraba

2. Module
Issues of Non-Modular Software
Issues of Modular Software

3. Motivation

4. -classpath
rt.jar

5. -classpath Issues
public is TOO Public
TOO Many Libraries
Which Libs Use which Libs?
Want to Hide “public” Class

6. rt.jar Issue
rt.jar
(Java SE 8)
Standard Library is TOO Huge

7. -classpath Issues
rt.jar Issue
Introduce Module
{ }Dependency
Disclosure Scope
Divide into Modules
According to Features

9. Module
JAR
module-info.java
Dependency
Disclosure Scope

10. Build
javac --module-path [directory] [source file]
-p
or
jar --create --file [JAR filename]
-C [class file directory] .

11. Build
javac --module-path [directory] [source file]
-p
or
jar --create --file [JAR filename]
-C [class file directory] .
Execution
java -p [directory]
--module [module]/[main class]
-m
or

12. java -p mods
-m net.javainthebox.jigsawsample/net.javainthebox.sample.Main
jigsawsample

13. java -p mods
-m net.javainthebox.jigsawsample/net.javainthebox.sample.Main
jigsawsample
javafx.media
javafx.controls

14. java -p mods
-m net.javainthebox.jigsawsample/net.javainthebox.sample.Main
jigsawsample
javafx.media
javafx.controls
javafx.graphics
javafx.base

15. java -p mods
-m net.javainthebox.jigsawsample/net.javainthebox.sample.Main
jigsawsample
javafx.media
javafx.controls
javafx.graphics
javafx.base
java.desktop
java.xml
jdk.jsobject
......
......
......

16. Tool Support
IDE IntelliJ IDEA
Eclipse
NetBeans
Only Nightly Build

17. Tool Support
IDE IntelliJ IDEA
Eclipse
NetBeans
Only Nightly Build
Build Tool Maven
Gradle
Need to Write Options
in Build File

18. jdeps Tool to Check Dependency

19. jdeps Tool to Check Dependency
C:samplemods>jdeps -s jigsawsample.jar
jigsawsample.jar -> java.base
jigsawsample.jar -> java.logging
jigsawsample.jar -> java.xml
jigsawsample.jar -> javafx.base
jigsawsample.jar -> javafx.controls
jigsawsample.jar -> javafx.graphics
jigsawsample.jar -> javafx.media

20. jdeps Tool to Check Dependency
C:samplemods>jdeps --generate-module-info .
jigsawsample.jar
writing to .jigsawsamplemodule-info.java
module jigsawsample {
requires java.logging;
requires javafx.base;
requires javafx.controls;
requires javafx.media;
requires transitive java.xml;
requires transitive javafx.graphics;
exports net.javainthebox.sample;
exports net.javainthebox.sample.internal;
}

21. jdeps Tool to Check Dependency
C:samplemods>jdeps --generate-module-info .
jigsawsample.jar
writing to .jigsawsamplemodule-info.java
module jigsawsample {
requires java.logging;
requires javafx.base;
requires javafx.controls;
requires javafx.media;
requires transitive java.xml;
requires transitive javafx.graphics;
exports net.javainthebox.sample;
exports net.javainthebox.sample.internal;
}
Edit as Necessary

22. Issues of
Non-Modular Software
Non-Disclosure API
Non-Standard Module

23. import com.sun.javafx.tk.FontMetrics;
import com.sun.javafx.tk.Toolkit;
import javafx.scene.text.Font;
public class FontSample {
public static void main(String... args) {
Font font = Font.font(24);
Toolkit toolkit = Toolkit.getToolkit();
FontMetrics metrics
= toolkit.getFontLoader().getFontMetrics(font);
System.out.println(metrics.getLineHeight());
}
}

24. C:fxsample>javac FontSample.java
FontSample.java:1: error: package com.sun.javafx.tk is not
visible
import com.sun.javafx.tk.FontMetrics;
^
(package com.sun.javafx.tk is declared in module javafx.
graphics, which does not export it to the unnamed module)
FontSample.java:2: error: package com.sun.javafx.tk is not
visible
import com.sun.javafx.tk.Toolkit;
^
(package com.sun.javafx.tk is declared in module javafx.
graphics, which does not export it to the unnamed module)
2 errors

25. import com.sun.javafx.tk.FontMetrics;
import com.sun.javafx.tk.Toolkit;
import javafx.scene.text.Font;
public class FontSample {
public static void main(String... args) {
Font font = Font.font(24);
Toolkit toolkit = Toolkit.getToolkit();
FontMetrics metrics
= toolkit.getFontLoader().getFontMetrics(font);
System.out.println(metrics.getLineHeight());
}
}

26. Non-Disclosure API
Non Exported Packages
com.sun...
sun...
java.awt.peer

27. Non-Disclosure API
Non Exported Packages
com.sun...
sun...
java.awt.peer
Exceptional API
sun.misc.Unsafe
sun.reflect.Reflection
(Remove in Future)

28. Solution
add export by
--add-exports option
--add-exports module/package=target
javac
java

29. Solution
add export by
--add-exports option
--add-exports module/package=target
javac
java
when non-modular system
target is ALL-UNNAMED
ex.
javac --add-exports javafx.graphics/com.sun.javafx.tk=ALL-UNNAMED
FontSample.java

30. public class FontSample {
public static void main(String... args) throws Exception {
Font font = Font.font(24);
FontMetrics metrics
= Toolkit.getToolkit().getFontLoader().getFontMetrics(font);
Class<FontMetrics> metricsClass = FontMetrics.class;
Field lineHeight
= metricsClass.getDeclaredField("lineHeight");
lineHeight.setAccessible(true);
System.out.println(lineHeight.getFloat(metrics));
}
}

31. C:fxsample>javac --add-exports
javafx.graphics/com.sun.javafx.tk=ALL-UNNAMED
FontSample.java
C:fxsample>java --add-exports
javafx.graphics/com.sun.javafx.tk=ALL-UNNAMED FontSample
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by FontSample (file:/C:/fxsa
mple/) to field com.sun.javafx.tk.FontMetrics.lineHeight
WARNING: Please consider reporting this to the maintainers of
FontSample
WARNING: Use --illegal-access=warn to enable warnings of
further illegal reflective access operations
WARNING: All illegal access operations will be denied in a futu
re release
31.921875

32. public class FontSample {
public static void main(String... args) throws Exception {
Font font = Font.font(24);
FontMetrics metrics
= Toolkit.getToolkit().getFontLoader().getFontMetrics(font);
Class<FontMetrics> metricsClass = FontMetrics.class;
Field lineHeight
= metricsClass.getDeclaredField("lineHeight");
lineHeight.setAccessible(true);
System.out.println(lineHeight.getFloat(metrics));
}
}

33. Non-Disclosure API
Reflection
Reflective access to public
--add-exports

34. Non-Disclosure API
Reflection
Reflective access to public
--add-exports
Reflective access to non-public
--add-opens in execution
using setAccessible(true)
ex.
java --add-opens javafx.graphics/com.sun.javafx.tk=ALL-UNNAMED
FontSample.java

35. import java.io.File;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;
import net.javainthebox.xml.Name;
public class JAXBSample {
public static void main(String... args) throws JAXBException {
JAXBContext context
= JAXBContext.newInstance("net.javainthebox.xml");
Unmarshaller unmarshaller = context.createUnmarshaller();
File file = new File("sakuraba.xml");
Name sakuraba = (Name)unmarshaller.unmarshal(file);
System.out.println(sakuraba.getFirst()
+ " " + sakuraba.getLast());
}
}

36. C:jaxbsample>javac JAXBSample.java
netjavaintheboxxmlName.java:11: error: package javax.xml.
bind.annotation is not visible
import javax.xml.bind.annotation.XmlAccessType;
^
(package javax.xml.bind.annotation is declared in module
java.xml.bind, which is not in the module graph)
<<skip the rest>>

37. import java.io.File;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;
import net.javainthebox.xml.Name;
public class JAXBSample {
public static void main(String... args) throws JAXBException {
JAXBContext context
= JAXBContext.newInstance("net.javainthebox.xml");
Unmarshaller unmarshaller = context.createUnmarshaller();
File file = new File("sakuraba.xml");
Name sakuraba = (Name)unmarshaller.unmarshal(file);
System.out.println(sakuraba.getFirst()
+ " " + sakuraba.getLast());
}
}

38. Non-Standard Module
Modules not included
in standard modulepath

40. Non-Standard Module
Modules not included
in standard modulepath
JAXB
JAX-WS
CORBA
java.xml.bind
java.xml.ws
java.corba
These modules will be removed in future
You should use the modules supplied by Java EE

41. Non-Standard Module
Modules not included
in standard modulepath
JAXB
JAX-WS
CORBA
java.xml.bind
java.xml.ws
java.corba
These modules will be removed in future
You should use the modules supplied by Java EE
Incubator jdk.incubator.httpclient

42. Solution
Add Modules by
--add-modules option
--add-modules module
javac
java
ex)
java --add-modules java.xml.bind JAXBSample

43. Issues of
Modular Software
modulepath
classpath

44. In Java SE 8, Only classpath is Used

45. In Java SE 8, Only classpath is Used
Module and Non-Module are Used
In Java SE 9,
modulepath classpath

46. In Java SE 8, Only classpath is Used
Module and Non-Module are Used
In Java SE 9,
modulepath classpath
specified in module-info.java
Module CAN Access Only Modules

47. foo.jar bar.jarmyapp.jar
Module Non-Module

48. foo.jar bar.jarmyapp.jar
Module Non-Module
Access Directly: Automatic Module
Access Indirectly: Unnamed Module

49. foo.jar bar.jarmyapp.jar
Module Non-Module
Access Directly: Automatic Module
Access Indirectly: Unnamed Module
Automatic Unnamed

50. foo.jar bar.jarmyapp.jar
Module Non-Module
Automatic Unnamed
modulepath classpath

51. foo.jar bar.jarmyapp.jar
Module Non-Module
Automatic Unnamed
modulepath classpath
Automatic Module: Named Module
Unnamed Module: No Name Modu
MANIFEST.MF Automatic-Module-Name
or JAR filename
Automatic Module Name is Defined by

52. foo.jar bar.jarmyapp.jar
Module Non-Module
Automatic Unnamed
modulepath classpath
module myapp {
requires foo;
}
> java -cp bar.jar -p mod
-m myapp/myapp.Main

53. foo.jar bar.jarmyapp.jar
java.xml.bind
Module Non-Module
Automatic Module Can’
Describe Dependency
t

54. foo.jar bar.jarmyapp.jar
java.xml.bind
Module Non-Module
Automatic Module Can’
Describe Dependency
t
> java -cp bar.jar -p mods
--add-modules java.xml.bind
-m myapp/myapp.Main

55. foo.jar bar.jarmyapp.jar
java.xml.bind
Module Non-Module
Automatic Module Can’
Describe Dependency
t
> java -cp bar.jar -p mods
--add-modules java.xml.bind
-m myapp/myapp.Main
> java -cp bar.jar -p mods
--add-modules ALL-MODULE-PATH
-m myapp/myapp.Main
If You Don’ t Know Dependencies

56. Conclusion
Non-Disclosure API
Issues of Non-Modular Software
Non-Standard Module
May Remove These APIs/Modules in Future
modulepath & classpath
Issues of Modular Software
May Use Only modulepath in Future??

57. Moving to Module
Issues & Solutions
Project Jigsaw
Java in the Box
Yuichi Sakuraba