systems-ucum should depend on systems-quantity

[mjog]

I just had cause to add systems-ucum (to access the troy-ounces constant) to an existing project that had only been using Indriya only, using the following:

    <dependency>
      <groupId>systems.uom</groupId>
      <artifactId>systems-ucum</artifactId>
      <version>2.2</version>
      <scope>compile</scope>
    </dependency>

And received the following stack as a result:

Caused by: java.lang.ClassNotFoundException: systems.uom.quantity.Drag
	at java.net.URLClassLoader.findClass(URLClassLoader.java:387)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
	at systems.uom.ucum.UCUM.<clinit>(UCUM.java:710)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:264)
	at tech.units.indriya.format.SymbolMap.<init>(SymbolMap.java:116)
	at tech.units.indriya.format.SymbolMap.of(SymbolMap.java:143)
	at systems.uom.ucum.format.UCUMFormat$Parsing.<clinit>(UCUMFormat.java:432)
	at systems.uom.ucum.format.UCUMFormat.getInstance(UCUMFormat.java:110)
	at systems.uom.ucum.spi.UCUMFormatService.<init>(UCUMFormatService.java:82)
	at systems.uom.ucum.spi.UCUMServiceProvider.getFormatService(UCUMServiceProvider.java:61)
[snip]

To resolve this, I also had to add the following:

    <dependency>
      <groupId>systems.uom</groupId>
      <artifactId>systems-quantity</artifactId>
      <version>2.2</version>
      <scope>runtime</scope>
    </dependency>

I would expect that if systems-ucum has a hard dependency on systems-quantity, then it should depend on it.

[keilw]

Thanks for pointing this out. There is a dependency between systems-quantity and the respective system modules, they should be the same, especially if new quantities are supported that were not before.

Normally you should not need the scope "compile", which is most likely why you needed to explicitly add systems-quantity. It is usually included/provided with each system module.

Please try 2.2.1-SNAPSHOT of each module, and let us know here, if the problem still exists if you use 2.2.1-SNAPSHOT for all relevant modules.

[mjog]

Apologies for the late reply, but after bumping javax.measure and systems.uom:systems-ucum to 2.2.1, and removing the explicit systems-quantity dependency, but I now get this from maven:

mjog@sable:~/path/to/project$ mvn compile -U
[INFO] Scanning for projects...
[INFO] 
[INFO] ------------------------------< mms:mms >-------------------------------
[INFO] Building RedactedProjectName dev
[INFO]   from pom.xml
[INFO] --------------------------------[ war ]---------------------------------
Downloading from central: https://repo.maven.apache.org/maven2/javax/measure/unit-api/2.2.1-SNAPSHOT/maven-metadata.xml
Downloading from central: https://repo.maven.apache.org/maven2/javax/measure/unit-api/2.2.1-SNAPSHOT/unit-api-2.2.1-SNAPSHOT.pom
[WARNING] The POM for javax.measure:unit-api:jar:2.2.1-SNAPSHOT is missing, no dependency information available
Downloading from central: https://repo.maven.apache.org/maven2/systems/uom/systems-ucum/2.2.1-SNAPSHOT/maven-metadata.xml
Downloading from central: https://repo.maven.apache.org/maven2/systems/uom/systems-ucum/2.2.1-SNAPSHOT/systems-ucum-2.2.1-SNAPSHOT.pom
[WARNING] The POM for systems.uom:systems-ucum:jar:2.2.1-SNAPSHOT is missing, no dependency information available
Downloading from central: https://repo.maven.apache.org/maven2/javax/measure/unit-api/2.2.1-SNAPSHOT/unit-api-2.2.1-SNAPSHOT.jar
Downloading from central: https://repo.maven.apache.org/maven2/systems/uom/systems-ucum/2.2.1-SNAPSHOT/systems-ucum-2.2.1-SNAPSHOT.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.064 s
[INFO] Finished at: 2026-02-25T20:59:13+11:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal on project mms: Could not resolve dependencies for project mms:mms:war:dev
[ERROR] dependency: javax.measure:unit-api:jar:2.2.1-SNAPSHOT (compile)
[ERROR] 	Could not find artifact javax.measure:unit-api:jar:2.2.1-SNAPSHOT in central (https://repo.maven.apache.org/maven2)
[ERROR] dependency: systems.uom:systems-ucum:jar:2.2.1-SNAPSHOT (compile)
[ERROR] 	Could not find artifact systems.uom:systems-ucum:jar:2.2.1-SNAPSHOT in central (https://repo.maven.apache.org/maven2)
[ERROR] 
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/DependencyResolutionException

Was I too late in testing this out?

[keilw]

Hi,
Please DO NOT bump javax.measure to 2.2.1 or 2.2.1-SNAPSHOT, unit-api, should use the jsr.version 2.2.

Could you try that please, it works on the CI-server for https://github.com/unitsofmeasurement/uom-systems.

[mjog]

Oh, okay sure. So this is the error when I bump systems.uom:systems-ucum only to 2.2.1-SNAPSHOT, and remove the explicit systems.uom:systems-quantity dep:

mjog@sable:~/path/to/project$ mvn compile -U
[INFO] Scanning for projects...
[INFO] 
[INFO] ------------------------------< mms:mms >-------------------------------
[INFO] Building RedactedProjectName dev
[INFO]   from pom.xml
[INFO] --------------------------------[ war ]---------------------------------
Downloading from central: https://repo.maven.apache.org/maven2/systems/uom/systems-ucum/2.2.1-SNAPSHOT/maven-metadata.xml
Downloading from central: https://repo.maven.apache.org/maven2/systems/uom/systems-ucum/2.2.1-SNAPSHOT/systems-ucum-2.2.1-SNAPSHOT.pom
[WARNING] The POM for systems.uom:systems-ucum:jar:2.2.1-SNAPSHOT is missing, no dependency information available
Downloading from central: https://repo.maven.apache.org/maven2/systems/uom/systems-ucum/2.2.1-SNAPSHOT/systems-ucum-2.2.1-SNAPSHOT.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.656 s
[INFO] Finished at: 2026-02-26T11:14:19+11:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal on project mms: Could not resolve dependencies for project mms:mms:war:dev
[ERROR] dependency: systems.uom:systems-ucum:jar:2.2.1-SNAPSHOT (compile)
[ERROR] 	Could not find artifact systems.uom:systems-ucum:jar:2.2.1-SNAPSHOT in central (https://repo.maven.apache.org/maven2)
[ERROR] 
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/DependencyResolutionException