[[_database]]

== Relational Database Setup

Out of the box, {{book.project.name}} persists its data using the Hibernate JPA set of APIs on top of an embedded Java based relational database.
The built-in database is not viable in high load and high concurrency situations.  It cannot be used in a cluster either.  It is
highly recommended that you replace the default embedded database with a more scalable and reliable solution like PostgreSQL or MySql.  This
chapter will show you how to configure {{book.project.name}} to use an external relational database.  It will also discuss
how you can configure the Hibernate JPA persistence abstraction that sits on top of your RDBMS.

NOTE:  Datasource configuration is covered much more thoroughly within the link:{{book.appserver.dataource.link}}[the datasource configuration chapter]
       of the {{book.appserver.admindoc.name}}.

=== RDBMS Checklist

These are the steps you will need to perform to get an RDBMS configured for {{book.project.name}}.

. Locate and download a JDBC driver for your database
. Package the driver JAR into a module and install this module into the server
. Declare the JDBC driver in the configuration profile of the server
. Modify the datasource configuration to use your database's JDBC driver
. Modify the datasource configuration to define the connection parameters to your database

This chapter will use PostgresSQL for all its examples.  Other databases follow the same steps for installation.

=== Package the JDBC Driver

Find and download the JDBC driver JAR for your RDBMS.  Before you can use this driver, you must package it up into a module.
Modules define JARs that are loaded into the {{book.project.name}} classpath and the dependencies those JARs have on
other modules.  They are pretty simple to set up.

Within the _.../modules/system/layers/keycloak/_ directory of your
{{book.project.name}} distribution, you need to create a directory structure to hold your module definition.  The convention is use the Java package name
of the JDBC driver for the name of the directory structure.  For PostgreSQL, create the directory _org/postgresql/main_.  Copy your database
driver JAR into this directory and also create an empty _module.xml_ file.

.Module Directory
image:../{{book.images}}/db-module.png[]

After you have done this, open up the _module.xml_ file and create the following XML

.Module XML
[source,xml]
----
<?xml version="1.0" ?>
<module xmlns="urn:jboss:module:1.3" name="org.postgresql">

    <resources>
        <resource-root path="postgresql-9.4.1208.jar"/>
    </resources>

    <dependencies>
        <module name="javax.api"/>
        <module name="javax.transaction.api"/>
    </dependencies>
</module>
----

The module name should match the directory structure of your module.  _org/postgresql_ maps to +org.postgresql+.  The
+resource-root path+ attribute should specify the JAR filename.  The rest are just the normal dependencies that
any JDBC driver JAR would have.