Helidon MP ValidationException in injecting MongoDB EntityManager

Question

I have started learning Helidon MP for a while yet, in tutorials and almost every source code I read based on this micro-service framework, examples are written on H2 database. I couldn't find any example based on MongoDB up to now. I already know about the JPA platform that eclipselink has developed for MongoDB and tried the guides in the JPA/NoSQL Examples. Besides, I could actually run the tests successfully in a simple maven project and creating the EntityManager object using factory directly works fine. But putting it in a Helidon MP project and using CDI for EntityManager like the instructions causes exception when I access http://localhost:8080/person/sahand with curl command. Before I put the related codes, I just found out that when Helidon creates EntityManager for a NoSQL database access, it should use org.eclipse.persistence.eis.EISLogin object while it's creating org.eclipse.persistence.sessions.DatabaseLogin causing a ClassCastException at some point and so on. This is the exception I get:

Caused by: Exception [EclipseLink-7108] (Eclipse Persistence Services - 2.7.7.v20200504-69f2c2b80d): org.eclipse.persistence.exceptions.ValidationException
Exception Description: This operation is not supported for non-relational platforms.
        at org.eclipse.persistence.exceptions.ValidationException.notSupportedForDatasource(ValidationException.java:590)
        at org.eclipse.persistence.internal.sessions.AbstractSession.getLogin(AbstractSession.java:2751)
        at io.helidon.integrations.cdi.eclipselink.CDISEPlatform.initializeExternalTransactionController(CDISEPlatform.java:228)
        at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.preConnectDatasource(DatabaseSessionImpl.java:851)
        at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.login(DatabaseSessionImpl.java:823)
        at org.eclipse.persistence.internal.jpa.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:258)
        at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:769)

This is the resource manager for database access:

@Path("/person")
@Dependent
public class PersonResourceManager {
    @PersistenceContext
    private EntityManager em;

    @GET
    @Path("/{name}")
    @Produces("text/plain")
    @Transactional
    public String getResponse(@PathParam("name") String name) {
        Query query = em.createQuery("Select p from PERSON p where p.name LIKE '" + name + "'");
        Person person = (Person) query.getResultList().get(0);
        return String.valueOf(person.getAge()) + "\n";
    }
}

Here is the Entity I'm trying to read from a MongoDB collection which is already created:

@Entity(name = "PERSON")
@NoSql(dataFormat = DataFormatType.MAPPED)
public class Person implements Serializable {
    @Id
    @GeneratedValue
    @Field(name = "_id")
    private String id;

    @Basic
    private String name;

    @Basic
    private int age;

    @Version
    private long version;

    @Deprecated
    protected Person() {}
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getId() {return id;}
    public String getName() {return name;}
    public void setName(String name) {this.name = name;}
    public int getAge() {return age;}
    public void setAge(int age) {this.age = age;}
}

These are the maven dependencies related to database resolved in the project:

<dependency>
    <groupId>javax.transaction</groupId>
    <artifactId>javax.transaction-api</artifactId>
    <version>1.2</version>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>javax.resource</groupId>
    <artifactId>connector-api</artifactId>
    <version>1.5</version>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>io.helidon.integrations.cdi</groupId>
    <artifactId>helidon-integrations-cdi-eclipselink</artifactId>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>io.helidon.integrations.cdi</groupId>
    <artifactId>helidon-integrations-cdi-jpa</artifactId>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>io.helidon.integrations.cdi</groupId>
    <artifactId>helidon-integrations-cdi-jta-weld</artifactId>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>io.helidon.integrations.cdi</groupId>
    <artifactId>helidon-integrations-cdi-datasource-hikaricp</artifactId>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>jakarta.persistence</groupId>
    <artifactId>jakarta.persistence-api</artifactId>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>org.mongodb</groupId>
    <artifactId>mongo-java-driver</artifactId>
    <version>3.12.6</version>
</dependency>
<dependency>
    <groupId>org.eclipse.persistence</groupId>
    <artifactId>eclipselink</artifactId>
    <version>2.7.7</version>
</dependency>
<dependency>
    <groupId>org.eclipse.persistence</groupId>
    <artifactId>org.eclipse.persistence.nosql</artifactId>
    <version>2.7.7</version>
</dependency>

Unit definition in persistence.xml file:

    <persistence-unit name="mongodb" transaction-type="RESOURCE_LOCAL">
        <class>sahand.example.helidon.Person</class>
        <properties>
            <property name="eclipselink.target-database" value="org.eclipse.persistence.nosql.adapters.mongo.MongoPlatform"/>
            <property name="eclipselink.nosql.connection-spec" value="org.eclipse.persistence.nosql.adapters.mongo.MongoConnectionSpec"/>
            <property name="eclipselink.nosql.property.mongo.port" value="27017"/>
            <property name="eclipselink.nosql.property.mongo.host" value="localhost"/>
            <property name="eclipselink.nosql.property.mongo.db" value="jpa-nosql-demo"/>
            <property name="eclipselink.logging.level" value="FINEST"/>
        </properties>
    </persistence-unit>

And finally a part of application.yaml that I guess is correct. However, I'm kind of sure that exception happens before even reading this configuration.

javax:
  sql:
    DataSource:
      person:
        dataSourceClassName: othatrg.eclipse.persistence.nosql.adapters.mongo.MongoPlatform
        dataSource:
          url: mongodb://localhost:27017
          user: sample_user
          password: "samplePass"

I would be really grateful if someone could help me with this. Although it's possible to create every EntityManager object by factory, I feel like this solution is messy. Either I'm using wrong dependency or something else I don't know about. This is also the instruction I followed for Helidon and JPA.

Answer 1

This was a bug in Helidon in the sense that the JPA subsystem in Helidon was calling the relational-database-specific method Session#getLogin() instead of the more apparently general-purpose Session#getDatasourceLogin() method.

The fix should be available in Helidon 2.0.2. While it is not guaranteed to fix this issue, it is the right thing for Helidon to do nonetheless.