Modularity in Java 9. Balázs Lájer Software Architect, GE HealthCare. HOUG Oracle Java conference, 04. Apr

Transcription

1 Modularity in Java 9 Balázs Lájer Software Architect, GE HealthCare HOUG Oracle Java conference, 04. Apr

2 Modularity in Java before Java 9 Source: 2

3 MANIFEST.MF Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: Osgi-example Bundle-SymbolicName: osgi-example Bundle-Version: qualifier Bundle-Activator: osgi_example.activator Bundle-RequiredExecutionEnvironment: JavaSE-1.8 Import-Package: org.osgi.framework;version="1.3.0" Export-Package: osgi.example.api Bundle-ActivationPolicy: lazy 3

4 MANIFEST.MF Manifest-Version: 1.0 Bundle-ManifestVersion: 2 Bundle-Name: Osgi-example Bundle-SymbolicName: osgi-example Bundle-Version: qualifier Bundle-Activator: osgi_example.activator Bundle-RequiredExecutionEnvironment: JavaSE-1.8 Import-Package: org.osgi.framework;version="1.3.0" Export-Package: osgi.example.api Bundle-ActivationPolicy: lazy 4

5 Modularity in Java - OSGi Services Bundle A v1.1.0 Bundle B v2.0.0 Service Registry Bundle A v1.0.0 Bundle C v1.1.0 Life Cycle Bundle B v1.0.0 Class loading OSGi Container 5

6 Modularity in Java OSGi OSGi: modularity on top of the Java platform Source: 6

7 Modularity of the platform Java 9 (Project Jigsaw) Source: 7

8 Modularity of the platform Java 9 (Project Jigsaw) The JDK is monolithic (JDK 7b65) 8 Source:

9 Modularity of the platform Java 9 (Project Jigsaw) 3 questions: Classpath Hell Is anything missing? Are there any conflicts? Is it safe to change a private API? 9 Source:

10 Modularity of the platform Java 9 (Project Jigsaw) Module path Module declaration: module-info.java module com.foo.bar { requires org.baz.qux; exports com.foo.bar.alpha; exports com.foo.bar.beta; } Module descriptor: module-info.class Module artifacts: modularized jar files JMOD? Source: 10

11 Modularity of the platform Java 9 (Project Jigsaw) Platform modules module java.base { exports java.io; exports java.lang; exports java.lang.annotation; exports java.lang.invoke; exports java.lang.module; exports java.lang.ref; exports java.lang.reflect; exports java.math; exports java.net;... } Source: 11

12 Modularity of the platform Java 9 (Project Jigsaw) module com.foo.bar { requires org.baz.qux; exports com.foo.bar.alpha; exports com.foo.bar.beta; } Source: 12

13 Modularity of the platform Java 9 (Project Jigsaw) module java.sql { requires public java.logging; requires public java.xml; exports java.sql; exports javax.sql; exports javax.transaction.xa; } Source: 13

14 Migration to Java 9: unnamed module Source: 14

15 Migration to Java 9: automatic modules Source: 15

16 Migration to Java 9: automatic modules Source: 16

17 Modularity of the platform Java 9 (Project Jigsaw) Services module java.sql { requires public java.logging; requires public java.xml; exports java.sql; exports javax.sql; exports javax.transaction.xa; uses java.sql.driver; } module com.mysql.jdbc { requires java.sql; requires org.slf4j; exports com.mysql.jdbc; provides java.sql.driver with com.mysql.jdbc.driver; } Source: 17

18 OSGi and Java 9 bundle lifecycle class loading / bundle module descriptor modularized JARs static services Java 9 dynamic servies OSGi container modularized platform OSGi bundle descriptors (Manifest) Class loading 18

19 OSGi and Java

20 Modularity of the platform Java 9 (Project Jigsaw) Private / Internal APIs banned sun.misc.unsafe The three most important rules of modularity are: Hide, Hide, and Hide. (Peter Kriens, Source: 20

21 Modularity of the platform Java 9 (Project Jigsaw) Proposal: - If it has a supported replacement in JDK 8 then we will encapsulate it in JDK 9; - If it does not have a supported replacement in JDK 8 then we will not encapsulate it in JDK 9, so that it remains accessible to outside code; and, further, - If it has a supported replacement in JDK 9 then we will deprecate it in JDK 9 and encapsulate it, or possibly even remove it, in JDK Source:

22 Java 9 (Project Jigsaw) JEP 200: The modular JDK JEP 201: Modular source code JEP 220: Modular run-time images JEP 260: Encapsulate most internal APIs JEP 261 / JSR 376: Java Platform Module System 22 Source:

23 Sources