Евгений Бова: "Modularity in Java: introduction to Jigsaw through the prism of OSGI"
•
0 likes•323 views
This document provides an introduction to modularity in Java using Jigsaw and OSGI. It discusses the problems with the current Java module system, including lack of encapsulation and unintuitive classpath lookups. The goals of Jigsaw are then outlined, including reliable dependencies, strong encapsulation, and improved performance. Key aspects of the new Jigsaw module system are explained, such as module descriptors, exports, requires, and services. Advanced concepts like optional and dynamic dependencies are also covered. Finally, the document compares Jigsaw to OSGI and notes they aim to solve similar issues, but OSGI is more dynamic while Jigsaw is simpler.
More Related Content
What's hot
What's hot (20)
Similar to Евгений Бова: "Modularity in Java: introduction to Jigsaw through the prism of OSGI"
Similar to Евгений Бова: "Modularity in Java: introduction to Jigsaw through the prism of OSGI" (20)
More from Anna Shymchenko
More from Anna Shymchenko (20)
Recently uploaded
Recently uploaded (20)
Евгений Бова: "Modularity in Java: introduction to Jigsaw through the prism of OSGI"
- 1. www.luxoft.com Modularity in Java: introduction to Jigsaw through the prism of OSGI Eugene Bova Software Developer at Luxoft July 2016
- 2. www.luxoft.com Short bio Java Developer at Luxoft 5 years of experience in Java Involved in the development of: - a huge OSGI based desktop application (600+ modules, 100+ thirdparty modules) - a middle-size web application
- 4. www.luxoft.com What is a module? com.example.alpha.Alpha com.example.alpha.AlphaFactory … com.example.alpha In Java modules are typically packaged as JAR files
- 5. www.luxoft.com SO, WHAT’S THE PROBLEM?
- 6. www.luxoft.com SO, WHAT’S THE PROBLEM? MODULES ARE NOTE ENCAPSULATED
- 7. www.luxoft.com Java Accessibility 1995-2016 public protected <package> private
- 8. www.luxoft.com Java Accessibility 1995-2016 public – accessible by every module protected – accessible by every module <package> - accessible by every module (unless package is sealed) private – accessible by current module
- 9. www.luxoft.com Problem statement Modules are not encapsulated - Non-API classes can be accessible by everyone Platform integrity can be violated - sun.misc.Unsafe – brings superpower. Classpath brings chaos - Class lookup is unintuitive - Class lookup is slow
- 11. www.luxoft.com
- 12. www.luxoft.com Goals of Jigsaw Reliable dependencies Strong encapsulation for modules Hide non-API types in JRE Improved performance A scalable Java SE Platform
- 13. www.luxoft.com Module Descriptor module com.example.alpha { } src/module-info.java src/com/example/alpha/Alpha.java src/com/example/alpha/AlphaFactory.java
- 14. www.luxoft.com module com.example.alpha { requires com.example.beta } com.example.alpha com.example.beta module com.example.beta { }
- 15. www.luxoft.com module com.example.alpha { requires com.example.beta } com.example.alpha com.example.beta module com.example.beta { exports com.example.beta.api // exports com.example.beta.internal.impl }
- 16. www.luxoft.com … Bundle-SymbolicName: com.example.alpha Require-Bundle: com.example.beta com.example.alpha com.example.beta … Bundle-SymbolicName: com.example.beta Export-Package: com.example.beta OSGI MANIFEST.MF
- 17. www.luxoft.com module com.example.alpha { requires com.example.beta requires java.sql } com.example.alpha java.sqlcom.example.beta
- 21. www.luxoft.com com.example.alpha java.sql java.logging java.sql.Driver d = … d.getParentLogger().log(…); package java.sql; public interface Driver { public java.util.Logger Logger getParentLogger(); // other methods //… }
- 22. www.luxoft.com com.example.alpha java.sql java.logging module com.example.alpha { requires java.sql; requires java.logging; }
- 23. www.luxoft.com com.example.alpha java.sql java.logging module java.sql { requires public java.logging; … } - reexports all accessible packages to downstream client - allows refactoring - in OSGI it’s called “reexport”
- 25. www.luxoft.com Qualified exports – exports for internal API module java.base { … exports sun.reflect; }
- 26. www.luxoft.com Qualified exports – exports for internal API module java.base { … exports sun.reflect to java.corba, java.logging, java.sql, java.sql.rowset, jdk.scripting.nashorn; } For modules collaborating at the implementation level Introduces tight couplings Can inadvertently make internal types accessible to modules other than those intended No analogy available in OSGI
- 27. www.luxoft.com Java Accessibility in JDK 9 public – accessible by every module public – accessible by specific module public – accessible within a module protected <package> private
- 30. www.luxoft.com Services module com.example.network.app { requires com.socket; } org.fastsocketcom.socket com.example.network.app
- 31. www.luxoft.com Services module com.example.network.app { requires com.socket; } org.fastsocketcom.socket com.example.network.app module com.socket { exports com.socket.api; exports com.socket.spi; uses com.socket.spi.NetworkSocketProvider } // com.socket.api.NetworkSocket.open(…) ServiceLoader<NetworkSocketProvider> sl = ServiceLoader.load(NetworkSocketProvider.class); Iterator<NetworkSocketProvider> it = serviceLoader.iterator();
- 32. www.luxoft.com Services module com.example.network.app { requires com.socket; } org.fastsocketcom.socket com.example.network.app module com.socket { exports com.socket.api; exports com.socket.spi; uses com.socket.spi.NetworkSocketProvider } module org.fastsocket { requires com.socket; provides com.socket.spi.NetworkSocketProvider with org.fastsocket.FastNetworkSocketProvider; } // com.socket.api.NetworkSocket.open(…) ServiceLoader<NetworkSocketProvider> sl = ServiceLoader.load(NetworkSocketProvider.class); Iterator<NetworkSocketProvider> it = serviceLoader.iterator();
- 33. www.luxoft.com A few advanced concepts…
- 34. www.luxoft.com Optional dependencies module org.joda.time { requires org.joda.convert; }
- 35. www.luxoft.com Optional dependencies module org.joda.time { requires static org.joda.convert; } Required at compile time Optional at runtime NoClassFoundException is possible Rarely used in OSGI. Not available in JDK build yet! http://mail.openjdk.java.net/pipermail/jpms-spec-experts/2016-June/000306.html - Discussion
- 36. www.luxoft.com Dynamic exports module org.example.app { requires hibernate.core; requires hibernate.entitymanager; exports com.example.app.model; }
- 37. www.luxoft.com Dynamic exports module org.example.app { requires hibernate.core; requires hibernate.entitymanager; exports dynamic com.example.app.model; } Package is accessible at runtime only Package presence is checked at compile time “exports dynamically … to ..” is possible No analogy available in OSGI. This is handled differently. Not available in JDK build yet! http://mail.openjdk.java.net/pipermail/jpms-spec-experts/2016-June/000307.html - Discussion
- 40. www.luxoft.com Compilation com.example.alpha com.example.beta $ javac -d mods/com.example.beta src/module-info.java src/com/example/beta/Beta.java
- 41. www.luxoft.com Compilation com.example.alpha com.example.beta $ javac -d mods/com.example.beta src/module-info.java src/com/example/beta/Beta.java $ javac -d mods/com.example.alpha -modulepath mods src/module-info.java src/com/example/alpha/Main.java
- 42. www.luxoft.com Launching $ java -modulepath mods -m com.example.alpha/com.example.alpha.Main module name main class
- 43. www.luxoft.com Things to take away - Jigsaw and OSGI aim to solve similar issues (sometimes in a similar way) - OSGI can’t solve Platform integrity issues - Jigsaw is static. OSGI is really dynamic. - OSGI has more features. Jigsaw is much simpler - It’s not a goal for Jigsaw to substitute OSGI!
- 44. www.luxoft.com WHAT ABOUT VERSIONING, DUDE???
- 46. www.luxoft.com More information http://openjdk.java.net/projects/jigsaw/ - OpenJDK project this has links to - related spec, requirements; - design overview; - quick start guide! http://openjdk.java.net/projects/jigsaw/ea - Early access build http://openjdk.java.net/projects/jigsaw/talks/ - Videos from Devoxx 2015
Editor's Notes
- Модуль -
- Модуль -
- Модуль -
- Модуль -
- Модуль -
- Модуль -
- Модуль -
- Модуль -
- no analogy in OSGI
- no analogy in OSGI
- no analogy in OSGI
- no analogy in OSGI
- no analogy in OSGI