Connecting WebSphere (WAS) Liberty to a JPA datasource

This discusses how to use JPA with WebSphere (WAS) Liberty profile. 
I used this article for an application.
Developing and running data access applications for the Liberty profile using WebSphere Application Server Developer Tools for Eclipse

I found I had to make some adjustments for my version.

First I got a a DB2 connection working and then MySQL

The key files:

server.xml

<dataSource id="db2" jndiName="jdbc/MyDataSource" type="javax.sql.DataSource">
    <jdbcDriver libraryRef="DB2JCC4Lib"/>
    <properties.db2.jcc databaseName="SAMPLE" user="user" password="{xor}MC9aaa="></properties.db2.jcc>
</dataSource>
<library id="DB2JCC4Lib">
    <fileset dir="c:/PROGRA~1/IBM/SQLLIB/java" includes="db2jcc4.jar,db2jcc_license_cu.jar"/>
</library>

This establishes the database credentials, the required jars and an JNDI name. Server.xml is straight forward. 

Persistance.xml

<persistence-unit name="CustomerQuery">
        <jta-data-source>java:comp/env/jdbc/SAMPLE</jta-data-source>
        <class>com.ibm.devworks.CustomerAccount</class>
        <!-- exclude-unlisted-classes>true</exclude-unlisted-classes -->
        <properties>
            <property name="openjpa.LockTimeout" value="30000" />
            <property name="openjpa.jdbc.TransactionIsolation" value="read-committed" />
            <property name="openjpa.Log" value="none" />
            <property name="openjpa.jdbc.UpdateManager" value="operation-order" />
            <property name="openjpa.jdbc.Schema" value="myschema"/>
            <property name="openjpa.ConnectionDriverName" value="com.ibm.db2.jcc.DB2DataSource"/>
        </properties>
    </persistence-unit>

There are a few things to note in this file:
-OpenJPA required the openjpa.ConnectionDriverName property and I was required to place the db2jcc4.jar within the Web Application lib directory in order for the class to be found.

- The jta-data-source includes a java:comp/env prefix. This is a resource reference defined in web.xml of the Web Application and not the JNDI name found in server.xml

web.xml
<resource-ref>
    <description>connection to SAMPLE</description>
    <res-ref-name>jdbc/SAMPLE</res-ref-name>
    <res-type>javax.sql.DataSource</res-type>
    <res-auth>Container</res-auth>
    <res-sharing-scope>Shareable</res-sharing-scope>
    <mapped-name>jdbc/MyDataSource</mapped-name>
    <lookup-name>jdbc/MyDataSource</lookup-name>
</resource-ref>

The things to note in this file:
The res-ref-name is set to jdbc/SAMPLE. This is the name that is listed in persistance.xml as 
<jta-data-source>java:comp/env/jdbc/SAMPLE. 
The lookup-name points to the JDNI name of the datasource listed in the server.xml. 

Code
Now you should be able to get a EntityManagerFactory in your code.
    @PersistenceUnit(unitName = "CustomerQuery")
    EntityManagerFactory emf; 

MySQL Setup

 To use MySQL, I created a new persistence-unit as shown below:

Persistance.xml

<persistence-unit name="CustomerQueryMySQL">
        <jta-data-source>java:comp/env/jdbc/SAMPLE</jta-data-source>
        <class>com.ibm.devworks.CustomerAccount</class>
        <!-- exclude-unlisted-classes>true</exclude-unlisted-classes -->
        <properties>
            <property name="openjpa.LockTimeout" value="30000" />
            <property name="openjpa.jdbc.TransactionIsolation" value="read-committed" />
            <property name="openjpa.Log" value="none" />
            <property name="openjpa.jdbc.UpdateManager" value="operation-order" />
           
        </properties>
    </persistence-unit> 

In this case, I did not have to provide a driver property.

web.xml

<resource-ref>
        <description>
        Auto Generated - SDO Datasource connection to SAMPLE</description>
        <res-ref-name>jdbc/SAMPLE</res-ref-name>
        <res-type>javax.sql.DataSource</res-type>
        <res-auth>Container</res-auth>
        <res-sharing-scope>Shareable</res-sharing-scope>
        <lookup-name>jdbc/MySQLDataSource</lookup-name>
 </resource-ref>

The JNDI name in the lookup-name property has changed to point to the MySQL database.

server.xml
<dataSource jndiName="jdbc/MySQLDataSource"  type="javax.sql.DataSource">
        <jdbcDriver>
            <library>
            <fileset dir="C:/software/mysql/lib" includes="mysql-connector-java-5.1.26-bin.jar"/>
            </library>
           
        </jdbcDriver>
        <properties databaseName="test" password="pass" portNumber="3306" serverName="localhost" user="nemo"/>           
    </dataSource>