Home/ Questions/Q 6761603
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-26T14:12:45+00:00

I’m trying to write a Play plugin that adds jar files to the Play

  • 0

I’m trying to write a Play plugin that adds jar files to the Play classpath at runtime. When onLoad is called it needs to load up a set of jars so that the JDT compiler can use them to resolve dependencies in the application classes. These jar files are not in the standard lib/ directory and therefore are not loaded up into the system classpath when Play starts.

Actually loading the jar file is not a problem, I’m going to specify each jar file I need as a URL and then pass those to an instance of URLClassLoader.

After a lot of research I’ve made the assumption that the classloader that Play uses is in Play.classloader and my initial plan was to create my own classloader that extends Play.ApplicationClassloader. This classloader would use an instance of URLClassLoader to find classes before delegating to the standard functionality in Play.ApplicationClassloader. I was then going to replace the Play classloader with my new instance:

Play.classloader = new MyExtensionClassLoader();

The problem I’m hitting is that the JDT compiler doesn’t seem to use the Play.classloader instance to load it’s classes.

So I have two questions:

What classpath is the JDT compiler actually using if it’s not using the Play.classloader instance?

More generally, does anyone have any suggestions how I load a jar into Play at runtime so that the JDT compiler can use it?

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    I don’t think that will work.

    Play has its own classloader which first checks if a class is “a managed play application class” (the one that gets compiled with the JDT compiler runtime), then it fallbacks to the parent classloader which is the default jvm-one..

    So all playframework-core classes and other libraries like Hibernate-classes are all loaded as regular classes from the default jvm-classloader.

    I hope you understand me 🙂

    -morten

    • 0