=== 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 and install it into the server. Modules define JARs that are loaded into the {project_name} classpath and the dependencies those JARs have on other modules. They are pretty simple to set up.

Within the _.../modules/_ directory of your {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 create an empty _module.xml_ file within it too.

.Module Directory
image:{project_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-9.4.1212.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. So, _org/postgresql_ maps to `org.postgresql`. The `resource-root path` attribute should specify the JAR filename of the driver.  The rest are just the normal dependencies that any JDBC driver JAR would have.

=== Declare and Load JDBC Driver

The next thing you have to do is declare your newly packaged JDBC driver into your deployment profile so that it loads and becomes available when the server boots up. Where you perform this action depends on your <<_operating-mode, operating mode>>. If you're deploying in standard mode, edit _.../standalone/configuration/standalone.xml_.  If you're deploying in standard clustering mode, edit _.../standalone/configuration/standalone-ha.xml_.  If you're deploying in domain mode, edit _.../domain/configuration/domain.xml_. In domain mode, you'll need to make sure you edit the profile you are using: either `auth-server-standalone` or `auth-server-clustered`

Within the profile, search for the `drivers` XML block within the `datasources` subsystem. You should see a pre-defined driver declared for the H2 JDBC driver. This is where you'll declare the JDBC driver for your external database.

.JDBC Drivers
[source,xml]
----
  <subsystem xmlns="urn:jboss:domain:datasources:4.0">
     <datasources>
       ...
       <drivers>
          <driver name="h2" module="com.h2database.h2">
              <xa-datasource-class>org.h2.jdbcx.JdbcDataSource</xa-datasource-class>
          </driver>
       </drivers>
     </datasources>
  </subsystem>
----

Within the `drivers` XML block you'll need to declare an additional JDBC driver.  It needs to have a `name` which you can choose to be anything you want.  You specify the `module` attribute which points to the `module` package you created earlier for the driver JAR.  Finally you have to specify the driver's Java class.  Here's an example of installing PostgreSQL driver that lives in the module example defined earlier in this chapter.


.Declare Your JDBC Drivers
[source,xml]
----
  <subsystem xmlns="urn:jboss:domain:datasources:4.0">
     <datasources>
       ...
       <drivers>
          <driver name="postgresql" module="org.postgresql">
              <xa-datasource-class>org.postgresql.xa.PGXADataSource</xa-datasource-class>
          </driver>
          <driver name="h2" module="com.h2database.h2">
              <xa-datasource-class>org.h2.jdbcx.JdbcDataSource</xa-datasource-class>
          </driver>
       </drivers>
     </datasources>
  </subsystem>
----