EclipseLink don't load properties from DataSource in Websphere Liberty Profile - jpa

Question

I have problem with configuring JPA in Websphere Liberty Profile. EclipseLink which is default provider in WAS with feature jpa-2.1 don't read the properties from created in server.xml DataSource. I've tried to get connection from this data source without JPA and this connection was succesfull, i had access to database. But when i use JPA and then create EntityManagerFactory from my PerstistenceUnit i get exception which in my opinion means that i didn't give required parameters such as url, username and password. I tested that WAS recognize EclipseLink provider, but now i don't know what can I do with this problem. Google haven't helped me.
Persistence.xml
<persistence version="1.0"
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_1_0.xsd">
<persistence-unit name="test-unit" transaction-type="JTA">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<jta-data-source>java:comp/env/jdbc/PostgreDS</jta-data-source>
<properties>
<property name="eclipselink.ddl-generation" value="drop-and-create-tables" />
<property name="eclipselink.ddl-generation.output-mode"
value="database" />
</properties>
</persistence-unit>
server.xml(only part with my setting of JDBC and DS)
<jdbcDriver id="myJDBCDriver" libraryRef="JDBCLib" javax.sql.XADataSource="org.postgresql.xa.PGXADataSource" >
</jdbcDriver>
<library id="JDBCLib" name="PostgreLib">
<file name="/home/hubert/JavaLibs/postgresql-9.4-1206-jdbc41.jar" id="JDBC_JAR"></file>
</library>
<dataSource id="PostrgreConnection" jdbcDriverRef="myJDBCDriver" jndiName="jdbc/PostgreDS" type="javax.sql.XADataSource">
<properties URL="jdbc:postgresql://localhost/GotSpotDB" databaseName="GotSpotDB" password="testtest" portNumber="5432" serverName="localhost" user="GotSpotAdmin"/>
</dataSource>
Logs
[ERROR ] CWWJP9992E: Exception [EclipseLink-4021] (Eclipse Persistence Services - 2.6.1.WAS-v20160106-a06c2b3): org.eclipse.persistence.exceptions.DatabaseException
Exception Description: Unable to acquire a connection from driver [null], user [null] and URL [null]. Verify that you have set the expected driver class and URL. Check your login, persistence.xml or sessions.xml resource. The jdbc.driver property should be set to a class that is compatible with your database platform
[ERROR ] SRVE0777E: Exception thrown by application class 'org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy:837'
javax.persistence.PersistenceException: Exception [EclipseLink-4021] (Eclipse Persistence Services - 2.6.1.WAS-v20160106-a06c2b3): org.eclipse.persistence.exceptions.DatabaseException
Exception Description: Unable to acquire a connection from driver [null], user [null] and URL [null]. Verify that you have set the expected driver class and URL. Check your login, persistence.xml or sessions.xml resource. The jdbc.driver property should be set to a class that is compatible with your database platform
at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:837)
at [internal classes]
at pl.almost.done.TestServlet.doGet(TestServlet.java:52)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
at [internal classes]
Caused by: Exception [EclipseLink-4021] (Eclipse Persistence Services - 2.6.1.WAS-v20160106-a06c2b3): org.eclipse.persistence.exceptions.DatabaseException
Exception Description: Unable to acquire a connection from driver [null], user [null] and URL [null]. Verify that you have set the expected driver class and URL. Check your login, persistence.xml or sessions.xml resource. The jdbc.driver property should be set to a class that is compatible with your database platform
at org.eclipse.persistence.exceptions.DatabaseException.unableToAcquireConnectionFromDriverException(DatabaseException.java:383)
... 4 more