org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create JDBC driver of class ''

I am doing a project on Eclipse Kepler using JPA 2.1, EclipseLink 2.5, Struts 1.3 and deployed on Tomcat 7.0. I create a project named JPADataSource. Under these conditions, my project works fine. While, when I add DataSources (MySQL) to the project, it does not work anymore. When I try to run the code, I get this error:

javax.persistence.PersistenceException: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create JDBC driver of class '' for connect URL 'jdbc:mysql://localhost:3306/playlist?autoReconnect=true'

I set everything in my code. This is my context.xml (placed in /JPADataSource/WebContent/META-INF/):

<?xml version="1.0" encoding="UTF-8"?>
<Context path="/JPADataSource">
    <WatchedResource>WEB-INF/web.xml</WatchedResource>
  <ResourceLink
    global="jdbc/playlist"
    name="jdbc/playlist"
    type="javax.sql.DataSource">
  </ResourceLink>    
</Context>

This is my persistance.xml:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="JPADataSource" transaction-type="RESOURCE_LOCAL">
        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
        <non-jta-data-source>java:comp/env/jdbc/playlist</non-jta-data-source>  
        <class>model.Singer</class>
        <class>model.Song</class>
        <class>model.User</class>
        <class>model.UserPlaylist</class>
    </persistence-unit>
</persistence>

And, at last, this is what I inserted under <GlobalNamingResources> in my server.xml (placed in /Server/Tomcat v7.0 Server at localhost-config/):

<Resource auth="Container" driverClass="com.mysql.jdbc.Driver" maxActive="100" maxIdle="30" maxWait="10000" name="jdbc/playlist" password="root" type="javax.sql.DataSource" url="jdbc:mysql://localhost:3306/playlist?autoReconnect=true" username="root"/>

What am I doing wrong? Or, what am I missing/misplacing?

Any help is apreciated.