Error using Hibernate with H2 in memory database

Question

I'm working with Hibernate. How can I configure my persistence.xml to have an H2 in-memory database?

My persistence.xml is:

<?xml version="1.0" encoding="UTF-8" ?>
<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" xmlns="http://java.sun.com/xml/ns/persistence">
    <persistence-unit name="persistenceUnit"
        transaction-type="RESOURCE_LOCAL">

        <class>com.mastertheboss.domain.Employee</class>
        <class>com.mastertheboss.domain.Department</class>
        <properties>

            <property name="javax.persistence.jdbc.driver" value="org.h2.Driver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:h2:mem:test;DB_CLOSE_DELAY=-1" />
            <property name="javax.persistence.jdbc.user" value="sa" />
            <property name="javax.persistence.jdbc.password" value="" />
            <property name="hbm2ddl.auto" value="update" />

            <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect" />
        </properties>

    </persistence-unit>
</persistence>

But when I run my app I get the following error:

Internal Exception: org.h2.jdbc.JdbcSQLException: Table "EMPLOYEE" not found; SQL statement: SELECT ID, NAME, DEPARTMENT_ID FROM EMPLOYEE [42102-171] Error Code: 42102 Call: SELECT ID, NAME, DEPARTMENT_ID FROM EMPLOYEE Query: ReadAllQuery(referenceClass=Employee sql="SELECT ID, NAME, DEPARTMENT_ID FROM EMPLOYEE")

Answer 1

You should set hibernate.hbm2ddl.auto property to "create" the first time you run your application, to create the tables

<property name="hibernate.hbm2ddl.auto" value="create" />

and then (if you don't want the tables to be recreated and emptied every time you start) set it to "validate".

<property name="hibernate.hbm2ddl.auto" value="validate" />

To create the schema automatically, add if-not-exists to your connection url like this:

<property name="hibernate.connection.url" value="jdbc:h2:~/<filename>;INIT=CREATE SCHEMA IF NOT EXISTS <schema_name>" />