Migrating Speedment to Java 9
Speaker: Dan Lawesson @dan_lawesson
See the list of all blog posts from the conference

Cute – Spire their mascot on github has two years experience in that role

Since a library, want to be running with Java 9 as soon as it is released.

Speedment

• Streams API ORM – customer.stream().filter(field.equal(value)).count();
• uses JVM memory acceleration, ode generation and modular design
• Type safety
• Works like streams – you don’t get any values back until terminal operation runs
• Have non-SQL code like a collector to convert the result into JSON
• can use findAny() with Optional on result – generates SQL limit statement
• Have finderBy so can join tables
• Like SQL, Streams are declared. Describe the what, not the how. But with SQL, you have to describe the result set format.

Jigsaw Effects/Problems

• A package must only belong to one modules. Yet it is common for two jars to have same package. The first one in the classpath takes precedence. In Java 9 must have only place for package.
• Automatic modules are for smoth transition to Java 9. It moves the Java 8 jars from the classpath to the module path. The jar automatically becomes a module
• However, automatic modules create split pakcages and can’t have those in Java 9
• sun.misc.Unsafe – should not be used but a key for real world Java success
• OSGi bundling is different than Jigsaw

Jigsawing the Java 8 open source application

• Running Java 8 under Java 9 JDK is easy
• Created module info file
• Brute force is to move all jars into depdencies in your monolithic module. When works, actually modularize app. Didn’t take this approach because already had OSGi modules
• Moduler approach: create directory for each module and move relevant packages to that directory. Add empty module-info.java (no requires/exports). That won’t compile so now can incrementally add dependencies and re-compile. Since this is iterative, they wrote a script to do it.
• Patch abuse of non-exported JDK APIs. Can add exports of java packages as a temporary workaround. Would need this flag at runtime if the temporary workaround isn’t removed. The workaround is just so you can identify all the issues and TBDs.
• Remove the OSGI bundling. Comment it out so building a jar instead of a bundle in Maven
• Use code generation so no reflection

Speedment Enterprise

• Harder becuase use sun.misc.Unsafe, third party dependencies with package issues

The first 20 minutes was about the Speedment library. I felt like that was a lot for a non-product talk. I wasn’t surprised because Dan was at my lunch table. And it was interesting. It just wasn’t necessary to understand the Java 9 part. Dan made a lot of references to things earlier in the day, which was nice. Also, the path Speedment took to move to Java 9 was very useful. I would have wanted to hear more about the issues in enterprise. Are they just outstanding issues. What do they plan to do if the libraries don’t release.