Accessing resource files from external modules

Question

So far until non-modularized java, you would simply put a file in src/main/java/resources make sure it is in classpath and then load it with

file = getClass().getClassLoader().getResourceAsStream("myfilename");  

from pretty much anywhere in the classpath.

Now with modules, the plot thickens.

My project setup is the following:

module playground.api {     requires java.base;     requires java.logging;     requires framework.core; } 

Config file is placed inside src/main/resources/config.yml.

Project is run with

java -p target/classes:target/dependency -m framework.core/com.framework.Main 

Since the main class does not reside in my own project, but in an external framework module, it can't see config.yml. Now the question is, is there a way to somehow put my config file into the module or open it up? Do I have to change the way file is loaded by framework upstream?

I tried using "exports" or "opens" in module-info but it wants to have a package name, not a folder name.

How to achieve this in best practical way so it would work as in Java 8 and with as little changes as possible?

Answer 1

// to scan the module path ClassLoader.getSystemResources(resourceName)  // if you know a class where the resource is Class.forName(className).getResourceAsStream(resourceName)  // if you know the module containing the resource ModuleLayer.boot().findModule(moduleName).getResourceAsStream(resourceName) 

See a working example below.

---

Given:

. ├── FrameworkCore │   └── src │       └── FrameworkCore │           ├── com │           │   └── framework │           │       └── Main.java │           └── module-info.java └── PlaygroundApi     └── src         └── PlaygroundApi             ├── com             │  └── playground             │      └── api             │          └── App.java             ├── config.yml             └── module-info.java 

Main.java could be

package com.framework;  import java.io.*; import java.net.URL; import java.util.Optional; import java.util.stream.Collectors;  public class Main {     public static void main( String[] args )     {         // load from anywhere in the modulepath         try {             URL url = ClassLoader.getSystemResources("config.yml").nextElement();             InputStream is = url.openStream();             Main.read(is);         } catch (IOException e) {             throw new RuntimeException(e);         }          // load from the the module where a given class is         try {             InputStream is = Class.forName("com.playground.api.App").getResourceAsStream("/config.yml");             Main.read(is);         } catch (ClassNotFoundException e) {             throw new RuntimeException(e);         }          // load from a specific module         Optional<Module> specificModule = ModuleLayer.boot().findModule("PlaygroundApi");         specificModule.ifPresent(module -> {             try {                 InputStream is = module.getResourceAsStream("config.yml");                 Main.read(is);             } catch (Exception e) {                 throw new RuntimeException(e);             }         });     }      private static void read(InputStream is) {         String s = new BufferedReader(new InputStreamReader(is)).lines().collect(Collectors.joining("\n"));         System.out.println("config.yml: " + s);     } } 

And you would launch with

java --module-path ./FrameworkCore/target/classes:./PlaygroundApi/target/classes \      --add-modules FrameworkCore,PlaygroundApi \        com.framework.Main 

To clone this example: git clone https://github.com/j4n0/SO-46861589.git