Hibernate, Guice and Play with Scala

Updated to play 2.4.2 with Guice and Hibernate 5.

About this project

This is an POC project to show that hibernate can integrate well with Scala and Play, without using nulls, java-bean accessors or too much boilerplate.

This project was extracted from another, under-development project. I did that hoping that it would be helpful to someone else like me; someone who doesn't think that ORMs are dead when you do functional programming.

I have done a lot of research on getting the persistence layer right for my scala based projects. And I have come to the conclusion that ORMs are here to stay for a while. I am constantly on the lookout for a good way to keep using an ORM (for CRUD or object graphs) with another framework like Slick or JOOQ (for complex queries).

Meanwhile, I have found a good way to make Hibernate work with scala's Option types and the scala accessor methods.

There is a companion blog post that I wrote which explains, in more detail, what I am trying to do with this project.

Disclaimer: Maintenance of this project is not a high priority for me right now. Also, I am aware that a lot of code in this project begs to be improved. I know 😑. But this was a personal POC kind of thing. My own project, for which I was doing this experiment, has a much cleaner structure.

Building and Running

Database

Set the username and password for a database user in conf/hibernate.properties. Make sure that this user can create tables since hbm2ddl.auto is set to update.

Environment

The application requires the path of aspectjweaver.jar as a value of ACTIVATOR_OPTS env variable before getting launched. This allows the weaver jar to be used as a javaagent to allow load-time weaving.

You can download aspectj-weaver.jar somewhere and specify its path in the launch file (in the root dir of the project) for the variable ACTIVATOR_OPTS.

The line looks like this:

export ACTIVATOR_OPTS="-javaagent:${userhome}/.ivy2/cache/org.aspectj/aspectjweaver/jars/aspectjweaver-1.8.2.jar"

Replace the path after "-javaagent:" with your download path.

Building the aspects

You won't need to do this step if you are not going to make any changes to the aspects related code located inside the "hibernate-property-access" dir.

To make load-time weaving work with third party classes in play, the aspects and the related classes need to be specified as a dependency. I'll write more about it later. This is true only for the development mode in play.

For that, I have created a small inner project inside the "hibernate-property-access" dir in the project's root dir. I can't use it as an sbt sub-project since that would make play use its application class-loader for its classes and that would defeat the whole purpose.

For the time being, I am doing the quickest possible thing. run sbt package inside "hibernate-property-access" dir and copy the generated jar into the "lib" dir of the root project. There are several ways this can be done better, but again, this is a POC. So, I am going to use the quickest way possible.

Run

Use the launch file in the root dir of this project to launch activator. It behaves in exactly same same way the activator command.

I am aware that I haven't created a launch.bat for windows users yet.

More Details

You can read this painfully long blog post if you want to understand the exact details of what I am doing in this project.