Java: Cannot read package from the unnamed module?

Question

While moving a project to Gradle, I stopped using my custom build of org.json which had a module-info.java fitted to it to comply to the module system. Now, I am using it via Maven normally, and as org.json is not a module by default, it gets put into the unnamed module.

My module-info looks like this:

open module mymodule { requires java.desktop; requires java.logging; }

I am getting the error:

SomeSourceFile.java: error: package org.json is not visible import org.json.*; ^ (package org.json is declared in the unnamed module, but module mymodule does not read it)

This is logical, except I don't know why my module doesn't read the unnamed module (the purpose of the unnamed module is full backwards compatibility with non-modular software so all packages are exported etc.), and how I could make my module read the unnamed module. As you can see, I have already tried making my module open to no avail.

You have to put the org.json jar on the module path - if it doesn't have a module descriptor, it will be an automatic module, which you can require. — Johannes Kuhn
– Johannes Kuhn, Commented Mar 20, 2021 at 2:14

Thiago Henrique Hupner · Accepted Answer · 2021-03-20 02:04:36Z

Probably updating the Maven Compiler Plugin (to 3.8.1, for instance) will do the trick.

<build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.8.1</version> </plugin> </plugins> </build>

The other thing will be to require the JSON module. From their pom.xml, I can see that they declare the Automatic-Module-Name as org.json (https://github.com/stleary/JSON-java/blob/master/pom.xml#L186)

So your module-info.java will become like this:

open module mymodule { requires java.desktop; requires java.logging; requires org.json; }

This is not a maven project, it is a gradle project using the maven repository for packages. But it does seem like maven is the only build system that can handle this conflict at the present time.
I don't have enough Gradle experience to help then, but this link might help
Well, this is one of the doc pages I have read several times over and it doesn't help.

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