<GlobalNamingResources>
   <Resource auth="Container" driverClassName="org.postgresql.Driver" maxIdle="30" maxTotal="100" maxWaitMillis="10000" name="jdbc/dsTriasEmployees" password="pwd" type="javax.sql.DataSource" url="jdbc:postgresql://localhost:5432/trias_employees" username="login"/>
</GlobalNamingResources>

<ResourceLink name="jdbc/dsTriasEmployees" global="jdbc/dsTriasEmployees"
        type="javax.sql.DataSource" />

DataSource datasource;

    public Connection connectJNDI() {
        try {
            Context initContext = new InitialContext();
            Context envContext = (Context) initContext.lookup("java:/comp/env");
            datasource = (DataSource) envContext.lookup("jdbc/trias_employees");
            Connection con = datasource.getConnection();
            genericLogger.info("JNDI LOOKUP -> " + con);
            return con;
        } catch (Exception ex) {
            genericLogger.error("JNDI LOOKUP -> " + ex);

        return null;
    }

javax.naming.NoInitialContextException: Need to specify class name in environment or system property, or as an applet parameter, or in an application resource file:  java.naming.factory.initial

<resource-ref>
      <description>
        DB PostgreSQL
      </description>
      <res-ref-name>
        jdbc/trias_employees
      </res-ref-name>
      <res-type>
        javax.sql.DataSource
      </res-type>
      <res-auth>
        Container
      </res-auth>
</resource-ref>

TomcatJNDI tomcatJNDI = new TomcatJNDI();
tomcatJNDI.processServerXml(File serverXml)
tomcatJNDI.processContextXml(contextXmlFile);
tomcatJNDI.start();

DataSource ds = (DataSource) InitialContext.doLookup("java:comp/env/jdbc/trias_employee")