Connection con=null;
    Class.forName("org.postgresql.Driver");
    out.println("<before create connection");
    con = (Connection) DriverManager.getConnection("jdbc:postgresql://192.168.0.130:5432/mydb","root", "root");
out.println("connection created");

<resource-ref>
  <description>
    Resource reference to a factory for java.sql.Connection
    instances that may be used for talking to a particular
    database that is configured in the <Context>
    configuration for the web application.
  </description>
  <res-ref-name>
    jdbc/EmployeeDB
  </res-ref-name>
  <res-type>
    javax.sql.DataSource
  </res-type>
  <res-auth>
    Container
  </res-auth>
</resource-ref>