DataSource dataSource = null;
try
{
    InitialContext ctx = new InitialContext();
    // comp/env is for component-environment bindings, such as web application bindings
    // this allows us to change the name later in the binding (in the ibm-web-bnd.xml file), instead of here in the code.

    dataSource = (DataSource) ctx.lookup("java:comp/env/jdbc/refDB");
}
catch (NamingException e)
{
    e.printStackTrace();
}

return dataSource.getConnection();

System.setProperty(Context.INITIAL_CONTEXT_FACTORY, "org.apache.naming.java.javaURLContextFactory");
System.setProperty(Context.URL_PKG_PREFIXES, "org.apache.naming");

InitialContext ctx = new InitialContext();

//"java:comp/env/jdbc/CacheDb" is the context that needs creating here.
ctx.createSubcontext("java:");
ctx.createSubcontext("java:comp");
ctx.createSubcontext("java:comp/env");
ctx.createSubcontext("java:comp/env/jdbc");

JdbcDataSource dataSource = new JdbcDataSource();
dataSource.setURL("jdbc:h2:mem:cachedb;DB_CLOSE_DELAY=-1"); // don't delete the database when the last connection closes

ctx.bind("java:comp/env/jdbc/CacheDb", dataSource);

System.setProperty(Context.INITIAL_CONTEXT_FACTORY,"com.ibm.websphere.naming.WsnInitialContextFactory");
System.setProperty(Context.URL_PKG_PREFIXES, "com.ibm.websphere.naming");