code: private void overrideFromSystemProperties() {
          String  url = System.getProperty("activejdbc.url");
          String  user = System.getProperty("activejdbc.user");
          String  password = System.getProperty("activejdbc.password");
          String  driver = System.getProperty("activejdbc.driver");
          if(!blank(url) && !blank(user) && !blank(driver)){
              connectionSpecMap.put(getEnvironment(), new ConnectionJdbcSpec(driver, url, user, password));
          }
  
          String  jndi = System.getProperty("activejdbc.jndi");
          if(!blank(jndi)){
              connectionSpecMap.put(getEnvironment(), new ConnectionJndiSpec(jndi));
          }
      }
docs: Overrides current environment's connection spec from system properties.