Practicing The Java Module System

Practicing The Java Module System presentation - Devoxx PL

Transcript

1. Practicing The Java Module System Rahman Usta Luxoft /rahmanusta /ustarahman
2. Agenda • Concept introduction • Practice times! http://bit.ly/java9-workshop 1. Generate JREs 2. Create a hello world module 3. Control access between modules 4. Using Auto-modules 5. Using Unnamed modules 6. Testing HTTP/2 Client API 7. Testing JSHell
3. Versions history 1995 ...> First release 1996 ...> Java 1.0 1997 ...> Java 1.1 (Reflection, JDBC) 1998 …> Java 1.2 (JIT, Swing) 2000 …> Java 1.3 (RMI, JNDI) 2002 …> Java 1.4 (Nio, Logging) 2004 …> Java 5 (Generics, Annotations) 2006 …> Java 6 (JDBC 4.0, Scripting) 2011 …> Java 7 (Project Coin, Fork-Join, Nio 2) 2014 …> Java 8 (Lambda, Method Ref, Stream API) 2017 …> Java 9 2018 (March) …> Java 10
4. Java 9 New features Jigsaw Related Changes • JEP 200 - The Modular JDK • JEP 201 - Modular Source Code • JEP 220 - Modular Run-Time Images • JEP 260 - Encapsulate Most Internal APIs • JEP 261 - Module System • JEP 282 - The Java Linker • JEP 238 - Multi-Release JAR Files 90+ new features http://openjdk.java.net/projects/jdk9/ • Other changes • Project Kulla (JShell) • HTTP/2 Client API • Flow API • Collections factories • API changes: Process API, • Stream API e.g.
5. Goals of the Project Jigsaw • To increase access control on the Java components • To increase security by removing access to propietry APIs • To increase performance of the Java platform • To get rid of the monolithic JDK • To modularize JDK source code • To bring Scalable JREs
6. Monolithic X Monolithic Kernel => Micro Kernel Monolithic Services => Micro Services Monolithic JDK => Modular JDK
7. Target scale Supercomputer Server Mac Embedded Kit
8. Java Runtime by module size
9. Practice time! Let’s create different scale of JREs with JLink tool. Resources: http://bit.ly/java9-workshop
10. What is Java module ? • Associated Java package(s) are grouped by a name. • Brings access control between modules $ java -d java.sql
11. JDK 9 Module Graph $JAVA_HOME/jmods
12. How to define a Java Module? Module definitions • exports • requires • opens • provides, with
13. New parameters for Java tools --p <module path> --module-path <module path>... A ; separated list of directories, each directory is a directory of modules. --add-modules Adds modules to resolution list -m <module>[/<mainclass>] Root module and main class
14. Practice time! Let’s create a modular Hello world! application • Create a module • Package a module • Run a module • Link a module with JRE
15. Modular Runtime Images
16. Access modifiers (< Java 9) Brings accessibility levels to Java components (class, method, field) • public • protected • package-private • private No Access Control on Package Level
17. Access modifiers (>= Java 9) Brings accessibility levels to Java components (module, class, method, field) public to all modules public only to specific module(s) public only to its own module private protected package Has Access Control on Package Level
18. Module accessibility #1
19. Module accessibility #2
20. Module accessibility #3
21. Qualified vs Unqualified exports Qualified Export package is readable by a spesific module exports com.a.b.c to com.to.a.module Unqualified Export package is readable by any module exports com.a.b.c;
22. Practice time! Let’s create printer service and printer client modules.
23. Named module Standard Java module declared with module-info.java Modules are loaded from --module-path For example: java --module-path lib/abc-1.0.jar;...
24. Automatic Module If a non-moduler JAR is added module path, it becomes an automatic module.
25. Practice time! Let’s use a non-modular JAR file in a modular Java application. • Auto-modules are helpful for migration • Uses jansi library to print colored texts!
26. Unnamed Module
27. Practice time! Let’s try to access from a non-module to a module • Check compile time access
28. Java 9 and Reflection Java Reflection API is one of the most helpful API for the library developers. Many open-source libraries use it for example: Hibernate, Spring Framework. • Access Java classes, modules, fields, methods, constructors e.g. • Create Java objects • Call Java methods • Access private methods and fields • Access annotations
29. Reflective Access between modules If a module want to access to other module’s components, other component have to open or export required packages to caller module. exports: Makes packages accessible to other modules at compile time or run time. opens: Makes packages accessible to other modules at run time including access to private members.
30. How to open a package or module Three ways: • opens com.a.b.c; • open module com.a.module { // open module } • --add-opens com.a.module/com.a.b.c=com.other.module
31. Practice time! Let’s practice reflective access between modules!
32. HTTP/2 Client API (an incubator module) module com.kodedu.http2 { requires jdk.incubator.httpclient; } HttpResponse response = HttpRequest .create(URI.create("https://devoxx.pl")) .GET() .response(); System.out.println(response.body(HttpResponse.asString()));
33. Practice time! Let’s run a HTTP/2 server and connect it via Java HTTP/2 Client API.
34. JShell ( Project Kulla) It is a REPL(read-eval-print-loop) tool for Java. tryjshell.org
35. Practice time! Let’s try JShell on your local and https://tryjshell.org
36. Thank you!