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How to determine MySQL / MariaDB version for Maven dependency?

I'm writing a simple Maven project to access my MySQL / MariaDB database. In order to download the proper database connector jar file, I'm adding the following Maven dependency:
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</version>
<scope>provided</scope>
</dependency>
I've got that 5.1.47 version above "by chance", based on a previous project which already worked on my computer.
However, when I type mysql -V (capital V) on terminal to check my MySQL/MariaDB version, I get the following:
>mysql -V
mysql Ver 15.1 Distrib 10.4.6-MariaDB, for Win64 (AMD64), source revision b8e655ce029a1f182602c9f12c3cc5931226eec2
But that 10.4.6 version doesn't mean much to me in terms of determining a proper version to set up my Maven dependency.
What's the procedure to determine MySQL version for Maven dependency based on my local MySQL / MariaDB server?

What's the procedure to determine MySQL version for Maven dependency
based on my local MySQL / MariaDB server?
You cannot .They are different things. The one specified in maven is the client version while one the you checked with mysql -V is the server version. The JDBC client version does not needed to be exactly matched with the server version.
Instead , the thing that you need to ensure is that the server support client version that you used.
From the official docs, 5.1.47 should support MySQL 5.61, 5.71, 8.0. And from the compatibility matrix of MariaDB , MariaDB 10.4.6 is comparability with MySQL 5.6 and 5.7 , which mean the JDBC client version that you are using should have no problem. But if it is possible , you can update the client to version 8.0 series , which is the official recommendation and should also work with your existing MariaDB version.

You can get the newest version from mvnrepository.
If you have the older version of mysql, you need to make sure, that the versions of the connector, jdbc, database etc. match. You can find this information in the mysql developer guide. The same thing applies to the compatibility for mariadb - check out the documentation.
Note, that the driver version depends not only on the version of the database, but also on java version.

I've checked MySQL connector MVN Repository for latest version, then I decided to replace 5.1.47 to 8.0.18.
However, after replacing to 8.x.x, I got "hibernate.dialect not set" error. So I added MySQL8Dialect to persistence.xml, then got "time zone value 'unknown' is unrecognized" error. So I added &serverTimezone=UTC to my connection parameters, than it worked.
Here is the updated persistence.xml after using 8.x.x:
<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd"
version="2.1">
<persistence-unit name="myunit" transaction-type="RESOURCE_LOCAL">
<properties>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost/databasename?useSSL=false&serverTimezone=UTC" />
<property name="javax.persistence.jdbc.user" value="user" />
<property name="javax.persistence.jdbc.password" value="password" />
<property name="hibernate.hbm2ddl.auto" value="update" />
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL8Dialect" />
</properties>
</persistence-unit>
</persistence>

Configuration of persistence.xml while using websphere 8.5.5.1

I'm coding an app that uses Servlet 3.0, Jsp, and JPA 2.0 and i'm deploying it into Websphere application server 8.5.
Since i already configured into the ibm websphere console, the data source and the jdbc driver, and the j2c authentification (i'm using oracle 11g as a database ). I dont know how my persistence.xml should look like, if i need to specify and add openJPA jars to my project.
For now anything i put into persistence.xml i'm having this issue :
Error 500: <openjpa-2.2.3-SNAPSHOT-r422266:1764177 fatal user error> org.apache.openjpa.persistence.ArgumentException
What should i do ? maybe i'm missing how JPA works
Thanks in advance

The OpenJPA jars should be provided by WebSphere and available to use for your application. There is a JPA sample available here: https://developer.ibm.com/wasdev/downloads/#asset/samples-Java_Persistence_API_JPA_Sample
In the sample, you can see an example of the persistence.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
<persistence-unit name="jpasamplepersistenceunit">
<jta-data-source>java:comp/env/jdbc/samplejpadatasource</jta-data-source>
<non-jta-data-source>java:comp/env/jdbc/samplejpadatasourcenonjta</non-jta-data-source>
<class>wasdev.sample.jpa.Thing</class>
<exclude-unlisted-classes>true</exclude-unlisted-classes>
<properties>
<!-- These properties are creating the database on the fly. We are using them to avoid users having
to create a database to run the sample.
See also the create=true line in the datasource meta data. -->
<property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema(ForeignKeys=true)" />
<property name="openjpa.jdbc.DBDictionary" value="derby" />
<!-- EclipseLink specific properties to create the database. They are only used if using the jpa-2.1 feature. -->
<property name="eclipselink.ddl-generation" value="drop-and-create-tables" />
<property name="eclipselink.ddl-generation.output-mode" value="both" />
</properties>
</persistence-unit>
</persistence>
I think your error is not caused by the OpenJPA jars not being available. It might be because your database is not configured correctly. Make sure your persistence.xml file refers to your datasources properly.

How to add missing columns in a multi-schema based multi-tenant web app using eclipselink

I'm developing a multi-tenant web app with "Shared Database/Separate Schemas" approach using java, jpa(eclipselink), mysql. My persistence file looks like:
<persistence-unit name="GroupBuilderPU" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<exclude-unlisted-classes>false</exclude-unlisted-classes>
<properties>
<property name="eclipselink.cache.shared.default" value="false"/>
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/?"/>
<property name="eclipselink.ddl-generation" value="create-or-extend-tables"/>
<--- Here goes other properties definition -->
</persistence-unit>
Now here is my EntityMangerFactory and EntityManager:
emfForTenant = Persistence.createEntityManagerFactory("GroupBuilderPU");
EntityManager em = emfForTenant.createEntityManager();
em.setProperty("eclipselink.tenant-id", schemaNameAsTenantId);
Its working fine untill I'm adding any new persistence column in any entity.
Like I've a Entity UserAccount where I've added a new column 'String rentalinfo' :
#Entity
#Multitenant(MultitenantType.TABLE_PER_TENANT)
#TenantTableDiscriminator(type = TenantTableDiscriminatorType.SCHEMA, contextProperty = PersistenceUnitProperties.MULTITENANT_PROPERTY_DEFAULT)
public class UserAccount implements Serializable {
...
private String rentalinfo;//Newly added column
...
}
Now after that this the following line is giving error:
em.createQuery("SELECT ua FROM UserAccount ua").getResultList();
The error is:
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'RENTALINFO' in 'field list'
So what will be the solution for adding new column (extend table) in this approach?

You are getting this exception because the 'RENTALINFO' column does not exist on your UserAccount table. Under normal circumstances, setting "create-or-extend-tables" will have EclipseLink issue an ALTER to your existing table, adding the new column. However, it would appear ddl generation is not supported for MultitenantType.TABLE_PER_TENANT: https://wiki.eclipse.org/EclipseLink/DesignDocs/Multi-Tenancy/TablePerTenant
Not supported:
Schema generation will not be supported since it requires knowledge of all the tenants (schema's) and further to that, access provision must be set once the tables are created if using schema level table per tenant.
So there is no ALTER and your table does not have the column.
As a side note, you can turn on EclipseLink SQL logging using the following persistence properties:
<properties>
<property name="eclipselink.logging.level" value="ALL"/>
<property name="eclipselink.logging.level.sql" value="FINE"/>
<property name="eclipselink.logging.parameters" value="true"/>
</properties>
This way, you can see what queries EclipseLink is (or in this case, isn't) executing.

Wildfly Data Persistence

I am currently working on a Java EE project and am working with the Wildfly server.
I have a Web project and EJB project which are deployed onto the Wildfly server.
I can save a user for example, but only for as long as the server is running.
There is no data persistence between server downtimes.
I have searched through the internet but couldn't find an answer.
My persistence.xml looks like this:
<persistence-unit name="primary">
<!-- If you are running in a production environment, add a managed
data source, this example data source is just for development and testing! -->
<!-- The datasource is deployed as WEB-INF/kitchensink-quickstart-ds.xml, you
can find it in the source at src/main/webapp/WEB-INF/kitchensink-quickstart-ds.xml -->
<jta-data-source>java:jboss/datasources/ExampleDS</jta-data-source>
<properties>
<!-- Properties for Hibernate -->
<property name="hibernate.hbm2ddl.auto" value="create-drop" />
<property name="hibernate.show_sql" value="false" />
<value="true"/>
</properties>
If I want to persist any information, do i need to reconfigure this file?
I hope you can help me :)

Your problem is this line
<property name="hibernate.hbm2ddl.auto" value="create-drop" />
Everytime when the wildfly starts up, JPA creates a new database model with an empty database.
Adjust your code to
<property name="hibernate.hbm2ddl.auto" value="update" />

You are using "ExampleDS" which is set up as H2 in-memory database by default. It therefore does not persist data between restarts on purpose (useful for development/testing). Go to wildfly's standalone/configuration/standalone.xml configuration file and search for "ExampleDS" in the "datasources" section. It should show:
<connection-url>jdbc:h2:mem:test;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE</connection-url>
where "mem" means in-memory. You can change "mem:test" to any write path, e.g.
<connection-url>jdbc:h2:~/test;DB_CLOSE_DELAY=-1</connection-url>
to use a H2 file-based database stored as "test" in your home-folder (assuming *nix).
You can also define additional databases (Postgresql, Oracle, etc) in the datasources-section.

DDL generation and general persistence.xml settings (OpenJPA)

Summary
I'm trying to run a Java web application JPA 2.0 example. The example application was written to run in Glassfish, using EclipseLink as JPA provider.
I would like to convert it to run in TomEE with OpenJPA as the JPA provider, but I can't any detailed tutorials for getting up and running with OpenJPA.
Problem
I'm having trouble converting persistence.xml to work with OpenJPA instead of EclipseLink. More specifically, the given persistence.xml doesn't specify:
Entity classes. Are these necessary?
The desired JPA provider. Will the container default to something?
The JDBC driver. How do I specify an "in-memory" DB (just for initial testing purposes)?
Also:
How are the DDL generation properties expressed in OpenJPA? I wasn't able to find them the OpenJPA User Guide.
Details
Below is the EclipseLink persistence.xml:
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
<persistence-unit name="order" transaction-type="JTA">
<jta-data-source>jdbc/__default</jta-data-source>
<properties>
<property name="eclipselink.ddl-generation" value="drop-and-create-tables" />
<property name="eclipselink.ddl-generation.output-mode"
value="both" />
</properties>
</persistence-unit>
</persistence>
I have the following Entity classes:
order.entity.LineItem
order.entity.LineItemKey
order.entity.Order
order.entity.Part
order.entity.PartKey
order.entity.Vendor
order.entity.VendorPart
Question
Does anyone know what the equivalent persistence.xml would look like for OpenJPA?
Alternatively, if anyone could point me to an OpenJPA tutorial that covers these issues that would be just as good

If you add the openjpa.jdbc.SynchronizeMappings property as shown below OpenJPA will auto-create all your tables, all your primary keys and all foreign keys exactly to match your objects
<property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema(ForeignKeys=true)"/>
Alternatively, you can use EclipseLink in TomEE by just adding the EclipseLink jars to <CATALINA_HOME>/lib/
refer here for Common PersistenceProvider properties

Foreign key constraints
The next line does not create foreign keys:
<property name="openjpa.jdbc.SynchronizeMappings"
value="buildSchema(ForeignKeys=true)"/>
Only creates schema and deletes content of a database.
But if you want create foreign keys, use the following lines:
<property name="openjpa.jdbc.SynchronizeMappings"
value="buildSchema(foreignKeys=true,schemaAction='dropDB,add')"/>
<property name="openjpa.jdbc.SchemaFactory"
value="native(foreignKeys=true)" />
<property name="openjpa.jdbc.MappingDefaults"
value="ForeignKeyDeleteAction=restrict, JoinForeignKeyDeleteAction=restrict"/>
See generated SQL
In another way, if you want to see the SQL output:
<property name="openjpa.Log"
value="DefaultLevel=TRACE,SQL=TRACE" />
NOTE: In order to see the generated output in the TomEE console, you need to change the log level in the file loggin.properties with openjpa.level = FINEST
See more in http://openjpa.apache.org/faq.html