Failing to create entity manager when running an app using module path

[grigoriliev]

I'm getting the following exception when trying to create an entity manager when running an app using module path, instead of using classpath:

Exception in thread "main" jakarta.persistence.PersistenceException: java.lang.NullPointerException
	at org.eclipse.persistence.jpa@4.0.0-M3/org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:861)
	at org.eclipse.persistence.jpa@4.0.0-M3/org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.getAbstractSession(EntityManagerFactoryDelegate.java:221)
	at org.eclipse.persistence.jpa@4.0.0-M3/org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.createEntityManagerImpl(EntityManagerFactoryDelegate.java:328)
	at org.eclipse.persistence.jpa@4.0.0-M3/org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:343)
	at org.eclipse.persistence.jpa@4.0.0-M3/org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:306)
	at com.example.modpathtest@1.0.0-SNAPSHOT/com.example.modpathtest.Main.main(Main.java:10)
Caused by: java.lang.NullPointerException
	at java.base/java.io.Reader.<init>(Reader.java:168)
	at java.base/java.io.InputStreamReader.<init>(InputStreamReader.java:76)
	at org.eclipse.persistence.core@4.0.0-M3/org.eclipse.persistence.internal.helper.DBPlatformHelper.load(DBPlatformHelper.java:163)
	at org.eclipse.persistence.core@4.0.0-M3/org.eclipse.persistence.internal.helper.DBPlatformHelper.loadFromResource(DBPlatformHelper.java:145)
	at org.eclipse.persistence.core@4.0.0-M3/org.eclipse.persistence.internal.helper.DBPlatformHelper.initializeNameToVendorPlatform(DBPlatformHelper.java:90)
	at org.eclipse.persistence.core@4.0.0-M3/org.eclipse.persistence.internal.helper.DBPlatformHelper.getDBPlatform(DBPlatformHelper.java:61)
	at org.eclipse.persistence.core@4.0.0-M3/org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.setOrDetectDatasource(DatabaseSessionImpl.java:265)
	at org.eclipse.persistence.core@4.0.0-M3/org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.loginAndDetectDatasource(DatabaseSessionImpl.java:808)
	at org.eclipse.persistence.jpa@4.0.0-M3/org.eclipse.persistence.internal.jpa.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:259)
	at org.eclipse.persistence.jpa@4.0.0-M3/org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:772)

Here is a test app, which can be run with 'mvn exec:exec':

eclipselink-module-path-test.zip

I think the problem is that DBPlatformHelper is trying to read 'org/eclipse/persistence/internal/helper/VendorNameToPlatformMapping.properties' using ClassLoader.getResourceAsStream but since package 'org.eclipse.persistence.internal.helper' is not opened unconditionally, getResourceAsStream returns null.

From getResourceAsStream javadoc:
"... this method will only find resources in packages of named modules when the package is opened unconditionally."

I guess, a quick fix for this would be to add:

opens org.eclipse.persistence.internal.helper;

to org.eclipse.persistence.core's module-info.java

[nedseb]

I have exactly the same issue ! If someone fixes it, I will be more than grateful