“Building and Testing Java 9 Applications with Gradle”
Speaker: Cédric Champeau
Deck on GitHub
For more blog posts from JavaOne, see the table of contents
- First version of Java that is not backward compatible
- Did review of Java 9 modules
- Gradle can run on Java 8 or 9.
- No built in support for module path
- Some plugins don’t work – ex: FindBugs. Will be hard to figure out if plugin or Gradle’s fault. Some mocking frameworks will require upgrade as well.
- Gradle 3.4 introduce a Java library plugin so can separate API and implementations dependencies. Just like modules!
Migrating to Java 9
- Sample app with 6 modules
- Uses reflection and service loader code so non trivial
- implementation (requires) vs api (transitive ok) – paves way for Java 9
- Replace META-INF/services with “provides” in module-info
- want to compile main and tests separately. is that one or two modules? if two modules, prevent from seeing each other.
- hack the java compiler task to give it the classpath as module path
- use a patch module so main and test code are one module and the tests can access the package private classes. Also gives JUnit the right to read the classes.
- so still compile separately but create one module
- “How many of you have a jar named util.jar?”
- Reserve automatic module name now by setting Automatic-Module-Name in the manifest
- They when upgrade to Java 9, use that name
- Said multi-release jars are a bad idea because odds are low the dependencies are the same
- Old way was to use reflection to determine which version available
- /src/main/java – shared sources
- /src/main/java9 – java 9 specific sources
- Tell gradle which versions of Java to compile each with and differences in dependencies
- ex: java9Implementation for dependencies – points it to shared sources
- Working on experimental jigsaw plugin which takes care of various tweaks demoed today. org.gradle.java.experimental-jigsaw
My take: This was interesting. I was a little distracted because I realized I needed to figure out a few presentation things for a larger room. So I was doing a little setup on my computer for tomorrow. It was hard to multi-task though. Cédric’s presentation was good and kept pulling me in :). Also the story teller app was cute. So I wasn’t satisfied in my level of paying attention or my level of getting ready for tomorrow. Oh well. I proved the downsides of “multi-tasking”.