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Apache Maven supports all Java (JokerConf 2018)
- 1. Apache Maven supports ALL Java ROBERT SCHOLTE @RFSCHOLTE
- 2. The good news Apache Maven runs fine on JDK 9 ( and 10 ) Apache Maven works like heaven on JDK 11 ( and 12-ea ) Possible issues are often plugin related Upgrading to the latest version should solve the problem
- 3. Applying a module descriptor 1. Just add your module-info.java to src/main/java 2. Upgrade maven-compiler-plugin to at least 3.8.0 3. There’s no step three Maven will calculate which dependencies belong to the classpath and which to the module path. No new dependency-element/scope
- 4. When two worlds collide…
- 7. Goals Java Platform Modular System Reliable configuration Strong encapsulation
- 8. The module-info.java module com.foo.module.name { // reliable configuration requires some.other.module; // strong encapsulation exports com.foo.package.name; }
- 9. If you’re not careful with your modularization you can corrupt the whole Maven Ecosystem Library builders should be aware of the impact of their module descriptors Application builders should recognize these issues
- 10. Revised specifications • Jars on modulepath • Support ALL-MODULE-PATH • Modulenames with numbers • Automatic module names
- 11. Jars on modulepath Original spec only allowed directories Maven dependencies point to a file Directory may contain multiple jars (javadoc,sources)
- 12. ALL-MODULE-PATH --add-modules ALL-MODULE-PATH In short: Make all entries on the module path see each other
- 13. Module names
- 14. Déjà Vu What is the proper module name? What is the proper groupId and artifactId?
- 15. Modulenames with numbers Project/product names • AWS-EC2 • AWS-Route53 • AWS-S3 • C3P0 • DB2 • Fabric8 • H2 • JSRnnn • OAuth2 Versioned libraries (includes versioned packages) • Commons-lang2 • Commons-lang3 Bridge libraries to different versions • Jspc-compiler-tomcatN • Mockwire-springN • Surefire-junitN Close to 30.000 groupId/artifactId end with a number (Central, March 2017)
- 16. Original implementation did not allow module names ending with a number.
- 17. #VersionsInModuleNames Some have argued that library maintainers will be tempted to encode major version numbers, or even full version numbers, in module names. Is there some way we can guide people away from doing that? Resolution Abandon the previous proposal to mandate that module names appearing in source-form module declarations must both start and end with “Java letters”. Revise the automatic-module naming algorithm to allow digits at the end of module names.
- 18. Module names must be as unique as the coordinates of dependencies
- 19. Automatic module names “… . The module name is otherwise derived from the name of the JAR file.”
- 21. Over 13500 ‘rows’ of collisions Evidence (OCT 2016)
- 22. JIGSAW Automatic modules are required for top- down adoption MAVEN References to automatic module names will cause collisions sooner or later Library builders should never refer to automatic modules* and deploy to a public repository. Application builders can choose to refer to automatic modules. * Filename based
- 23. Application versus library Application Module descriptor without exports maven-compiler-plugin logs info message in case of automatic module usage Library Module descriptor with exports Tip: Use Maven 3.5.0+ for colour support maven-compiler-plugin logs WARNING message in case of automatic module usage
- 24. Automatic modules Ease of top-down migration for application builders But what about “in the middle” library builders?
- 25. Java Platform. It will be approachable, i.e., easy to learn and easy to use, so that developers can use it to construct and maintain libraries and large applications for both the Java SE and Java EE Platforms. JSR 376: JavaTM Platform Module System Original Java Specification Request (JSR) Section 2.1
- 26. Application my-app Libraries jackson-core jackson-databind jackson-annotations my-lib java.base Conference example
- 27. Application my-app Libraries (direct deps) … … … my-lib Libraries (transitive deps) … … … … Libraries (independent deps) jackson-core jackson-databind jackson-annotations java.base More realworld example
- 32. 5animalmarket-1.0.jar module com.animalmarket { requires org.moneylibs.buy; requires org.moneylibs.sell; }
- 33. <project> <modelVersion>4.0.0</modelVersion> <groupId>com.animalmarket</groupId> <artifactId>animalmarket</artifactId> <version>1.0.0-SNAPSHOT</version> <dependencies> <!-- the dependencies --> </dependencies> </project>
- 35. animalmarket.jar (com.animalmarket) requires o.m.buy; requires o.m.sell; buy-service-1.0.jar (o.m.buy) requires currency; sell-service-1.0.jar (o.m.sell) requires o.m.currency;
- 36. animalmarket.jar (com.animalmarket) requires org.moneylibs.buy; requires org.moneylibs.sell; buy-service-1.0.jar (o.m.buy) requires currency; currency-1.0.jar (currency) sell-service-1.0.jar (o.m.sell) requires org.moneylibs.currency; currency-2.0.jar (o.m.currency)
- 37. animalmarket.jar (com.animalmarket) requires o.m.buy; requires o.m.sell; buy-service-1.0.jar (o.m.buy) requires currency; currency-1.0.jar (currency) sell-service-1.0.jar (o.m.sell) requires o.ms.currency; currency-2.0.jar (o.m.currency)
- 39. animalmarket.jar (com.animalmarket) requires o.m.buy; requires o.m.sell; sell-service-1.0.jar (o.m.sell) requires o.m.currency; currency-2.0.jar (o.m.currency) buy-service-1.0.jar (o.m.buy) requires currency; currency-1.0.jar (currency)
- 40. animalmarket.jar (com.animalmarket) requires o.m.buy; requires o.m.sell; sell-service-1.0.jar (o.m.sell) requires o.m.currency; currency-2.0.jar (o.m.currency) buy-service-1.0.jar (o.m.buy) requires currency; currency-1.0.jar (currency)
- 43. Point of no return “If you refer to dependency X:N as a module and dependency X:N-1 has no module name, then you cannot downgrade this dependency anymore”
- 45. Strong advices -Project must be Java 9 ready!! o No split packages o No root classes -For libraries that depends on at least one filename based automodule: o Help depending projects by providing intended module name via MANIFEST -Pick your modulename with care, e.g. the shared package
- 46. Mistakes will happen In fact, first invalid modules are already available at Maven Central asm-6.0_BETA ( org.ow2.asm) asm-all-6.0_BETA (org.ow2.asm.all) 1 asm-debug-all-6.0_BETA (org.ow2.asm.debug.all) 1 Application developer cannot fix these mistakes (dependency-exclude doesn’t work) 1 Fixed with asm-6.0 by dropping *-all artifacts (asm includes debug information by default) Same packages must have the same modulename (otherwise potential split package issue)
- 47. Tips for using JAVA 9 with MAVEN DON’T change your folder structure (no need for extra folder with module name) Modulepath or classpath? No change to dependencies, just add module- info.java ( Plexus-java can help plugins to build up the path )
- 48. Understanding plexus-java Maven independent library for general Java features ◦ LocationManager ◦ Version Used by ◦ maven-compiler-plugin ◦ maven-failsafe-plugin ◦ maven-javadoc-plugin ◦ maven-jlink-plugin ◦ maven-jmod-plugin ◦ maven-surefire-plugin ◦ …
- 49. Plexus Java :: LocationManager If there’s a module descriptor, all its direct and indirect required modules will be put on the module path, the rest on the classpath Most plugins show the paths as debug logging ( -X / --debug ) Learn the JPMS specifications
- 50. JLINK “You can use the jlink tool to assemble and optimize a set of modules and their dependencies into a custom runtime image” Enhanced solution for fat executable jar However… it is overrated Only works with explicit modules!
- 51. Source / target 1.9 <release>9<release> source/target <= 1.8 : animal-sniffer
- 52. Issues? 1) Stackoverflow 2) Apache Maven mailinglists 3) Apache Maven Jira in case of bugs / improvements
- 54. Can every project become modular? NO -Java 9 is a gamechanger, it introduces new rules -The older the project, the more likely it cannot follow these rules -No worries, the classpath is still there and will stay!
- 55. The boomerang question Or “the ever returning Maven/JavaNEXT/Conference question” Will Maven generate the module descriptor?
- 56. No Different purpose ◦Pom is used to download jars and make them available ◦Module descriptor is used to specify required modules Not all modules are dependencies ◦( e.g. java.logging, jdk.compiler )
- 57. Module descriptor elements not covered: ◦Module name ◦Open module ◦Exported packages ◦Uses / provides services Pom 4.0.0 has no space for new elements
- 58. Pom hygiene dependency:analyse ◦ Analyzes the dependencies of this project and determines which are: ◦used and declared (good) ◦used and undeclared (via transitive dependency) ◦unused and declared (ballast!) Dependencies can be excluded, required modules cannot
- 59. …BUT JDEPS can do it, right? Can create a rough module descriptor Intended to help with an initial descriptor Uses binary classes, i.e. AFTER compile-phase
- 60. Some open source project will… https://github.com/moditect/moditect
- 61. [RESULT] Apache Maven supports ALL Java
- 62. Up-for-grabs ~60-80% of Java Project/Developers use Maven The Apache Maven Project holds ~95 (sub)projects Maintained by ~5-10 active volunteers (No Company!) Let’s restore the balance! https://s.apache.org/up-for-grabs_maven https://maven.apache.org/guides/development/guide-committer-school.html