How to verify entity manager can establish a connection to the database?

Question

persistence.xml

<?xml version="1.0" encoding="UTF-8"?>

<persistence 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"
version="2.0">

<persistence-unit name="prod" transaction-type="JTA">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <class>webadmin.domain.WebSite</class>
    <exclude-unlisted-classes>false</exclude-unlisted-classes>

    <properties>
        <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect" />
        <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver" />
        <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/dummy?useUnicode=yes&amp;characterEncoding=utf8;" />
        <property name="hibernate.connection.username" value="root1" />
        <property name="hibernate.connection.password" value="root1" />

    </properties>

</persistence-unit>

Service

@Stateless
public class WebSiteService {
@PersistenceContext(unitName = "prod")
private EntityManager entityManager;

public WebSite saveWebSite(WebSite webSite) {
    System.out.println("before query");
    Query q=entityManager.createNativeQuery("insert into dum values (1, 'ws');");
    System.out.println("before execution");
    q.executeUpdate();
    System.out.println("after execution");

Problem

I'm fighting an org.hsqldb.HsqlException: user lacks privilege or object not found: DUM issue. While trying to find the root cause, I have updated my persistence.xml with an invalid database name and invalid user/password. Yet, I see no exceptions related to this. So I believe that even using correct parameters, I simply never connect to the database. What's missing here? How can I check such connection is made?

TomEE 1.6, MySQL 5.

Solution

Going with JB's comment that TomEE requires a datasource to be defined in tomee.xml, so add the data source there.

<tomee>
    <Resource id="prodDataSource" type="javax.sql.DataSource">
    jdbcDriver com.mysql.jdbc.Driver
    jdbcUrl jdbc:mysql://localhost:3306/yourdbname
    jtaManaged true
    password root
    userName root
    InitialSize 50 
    MaxActive 100
    MaxIdle 3   
    </Resource>
</tomee>

No-one else has access to my server, so I'm keeping the credentials in tomee.xml. That way, my persistence.xml properties section is reduced to this:

<properties>
    <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect" />
    <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver" />
</properties>

Remove project from the server. Double click on the server to go to server overview. Under server locations: choose Tomcat installation directory. Clean server, project, restart. Worked for me.

A valuable comment from RajV: How to define MySQL data source in TomEE?

Answer 1

You have to configure a DataSource for your MySQL database: http://tomee.apache.org/configuring-datasources.html

And then you have to follow the Tomee documentation about Hibernate: http://tomee.apache.org/tomee-and-hibernate.html. Note the use of

<jta-data-source>movieDatabase</jta-data-source>

to reference the datasource (movieDatabase) configured in the first step.