No suitable driver found for jdbc:mysql://localhost:3306/rom (Payara 5, Windows 10) - jpa

Question

Believe me, I know this question has been asked many times and has gotten an answer many times, and these answers seemed to have worked for some users. I've spent many hours trying the various proposed solutions and, while they work on Linux (Ubuntu) they seem to have no effect on Windows (Windows 10 Home with jdk1.8.0_161). The web application is using EclipseLink 2.5.0 for persistence.
I've tried including the mysql-connector-java-5.1.46-bin.jar file in the WAR archive (WEB-INF/lib; using the Deployment Assembly screen in Eclipse), copying it to the payara5/glassfish/lib folder, as well as the payara5/glassfish/domains/domain1/lib/ and payara5/glassfish/domains/domain1/lib/applibs folders. I also tried specifying the library when deploying the web application, i.e., putting mysql-connector-java-5.1.46-bin.jar as the value in the library field. I updated the CLASSPATH environment variable with the path to the JAR file. Every time, the server was restarted. None of these actions have any effect. Note that they did work on Linux Ubuntu.
See below for the well-known exception trace:
Local Exception Stack:
Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.7.0.v20170811-d680af5): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: java.sql.SQLException: No suitable driver found for jdbc:mysql://localhost:3306/rom
Error Code: 0
at org.eclipse.persistence.exceptions.DatabaseException.sqlException(DatabaseException.java:331)
at org.eclipse.persistence.exceptions.DatabaseException.sqlException(DatabaseException.java:326)
at org.eclipse.persistence.sessions.DefaultConnector.connect(DefaultConnector.java:138)
at org.eclipse.persistence.sessions.DatasourceLogin.connectToDatasource(DatasourceLogin.java:170)
at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.setOrDetectDatasource(DatabaseSessionImpl.java:228)
at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.loginAndDetectDatasource(DatabaseSessionImpl.java:804)
at org.eclipse.persistence.internal.jpa.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:254)
at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:757)
at org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.getAbstractSession(EntityManagerFactoryDelegate.java:216)
at org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.createEntityManagerImpl(EntityManagerFactoryDelegate.java:324)
at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:348)
at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:311)
...
Any thoughts would be greatly appreciated.
UPDATE: as a sanity check (got the idea thanks to #Abhi) I added the line
try {
System.out.println("JDBC driver: " +
Class.forName("com.mysql.jdbc.Driver"));
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
Which correctly prints the following line (without throwing an exception):
JDBC driver: class com.mysql.jdbc.Driver
But does nothing to solve the problem. In other words, the driver seems to be loadable but somehow EclipseLink is not able to find it (?)

Answer 1

Looks like I'm able to answer my own question. I asked the exact same question on the Payara Forum and was recommended to define a data source instead of using the driver directly (#Chris pointed in this direction as well). A data source is likely the best way to go anyway but I wanted to avoid the complexity and use the simplest setup .. which clearly didn't work.
For reference, you can find the working setup below:
In Payara 5, goto JDBC > JDBC Connection Pools > New: enter a pool name, select javax.sql.DataSource as resource type, and MySql as vendor. On step 2, com.mysql.jdbc.jdbc2.optional.MysqlDataSource should be preselected for Datasource Classname. Fill out the Username and Password (e.g., root, changeit) properties under the Additional Properties header. Select finish. On the page for the newly created connection pool, select PING to make sure it was setup correctly.
In your persistence.xml file, make sure the persistence-unit element starts as follows:
<persistence-unit name="ROM" transaction-type="JTA">
<jta-data-source>java:global/<connection pool name></jta-data-source>
Create a web.xml file (this may also be done using Java Annotations):
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
version="3.1">
<data-source>
<name>java:global/<connection pool name></name>
<class-name>com.mysql.jdbc.jdbc2.optional.MysqlDataSource</class-name>
<server-name>[host name, e.g., localhost]</server-name>
<port-number>3306</port-number>
<database-name>[db name]</database-name>
<user>[username, e.g., root]</user>
<password>[password]</password>
</data-source>
</web-app>
This configuration worked for me at least. Hoping this will help someone else down the road. Note that there are various useful settings for a connection pool - see e.g., here for more options.

Answer 2

to the line of code to connect:
con = DriverManager.getConnection(urlBaseDatos, usuario, clave);
Add the following:
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
con = DriverManager.getConnection(urlBaseDatos, usuario, clave);

Answer 3

Naturally I concur with the answer here, which is "in an Application server you should use a DataSource".
Now just my two cents and to answer the original question:
From JDBC 4, you aren't required to register the driver anymore, and this line shouldn't be necessary:
DriverManager.registerDriver(new com.mysql.cj.jdbc.Driver());
See: https://docs.oracle.com/javase/8/docs/api/java/sql/DriverManager.html
So when using a JDK8+/EE8/JDBC4.2 compliant application server, you shouldn't be mandated to register the driver. Or so I thought...
Though, like you #William, I noticed Glassfish/Payara requires it. It's very strange. Maybe it has to do with the way it handles classloading?
Wildfly, in turn, does the right thing and automatically loads the driver without actually having to manually register it.