I’ve been listening many things about new releases of java and jigsaw feature for more than year. Sometimes it seems that you are the only one person who haven’t tried java9 yet. Anyway, it is necessary to move with the times, that’s why I decided to use java 10 in some personal activities. By june 2018, I got following conclusions:
- Jigsaw is cool and not complicated
- Jigsaw will make you keep your packages in order
- Almost everything is not ready for Jigsaw, migration features like automatic module won’t help in complicated project
- You won’t get everything in order in your project in a moment.
- If your project is enough big, better not hurry… (actually always truth:))
I worked with several java 10 projects. The first group is a number of almost similar microservices: maven spring boot projects with several maven (java) modules. For example, one of them has REST endpoint, some business logic and connection to postgres replica through spring-data. All of them were founded in java 10 from the beginning. Also, I decided to move my simple library to java 10 as a simplest project.
Jigsaw is cool and not complicated
The main feature of java9 is a jigsaw system of java modules. A package and a classname now define the only one class that you may use - the main advantage and pain of the new java. If it works, it provides:
- Safety, you better know what is happening in your code by changing access settings
- Order in dependencies. If two dependencies exports the same package, you have to exclude one by dependency manager. Often it happens with different versions of the same libs.
- Advanced encapsulation
However, it won’t appear after you move to next java, because migration process is rather flexible and designed not for getting it right now, better to say, it provides a proper direction.
Jigsaw will make you keep your packages in order
Since access to class is described on package level, a developer must design packages thinking about level of access for each one. I expect it will improve code quality (especially in enterprise) because everybody will have to pay attention to it.
Almost everything is not ready for Jigsaw
By the middle of 2018 almost all open source libs haven’t migrated to module system yet. Jigsaw engineers tried to simplify migration by using automatic modules. It means, if your code has old style dependency without java modules, this jar is considered as one java module. Your responsibility is to exclude all repeated packages from all imported modules by dependency manager. Sometimes it is impossible without broken application. For example, I couldn’t add swagger to my spring boot application. I guess, that complicated projects may have many such points, so better wait until some dependencies become modular.
Also I had troubles with travis and jitpack services. They do not support jdk 10, however they support jdk 9.
You won’t get everything in order in your project in a moment
Automatic module is reluctant instrument to provide migration. It is like cleaning some application from the top, but leaving some dirty dependencies untouched. It looks good but we know what is inside :). Then updating such dependencies will remove unnecessary dependencies and make system more clean and elegant.