我正在使用下面这样的文件中的config loader，但驱动程序并没有从config中看到环境变量并抛出 com.datastax.oss.driver.api.core.auth.AuthenticationException: Authentication error on node /105.0.153.68:9042: server replied with 'Provided username ${CASSANDRA_USR} and/or password are incorrect' to AuthResponse request 我怎样才能解决这个问题？
java代码

File confFile = new File("config/application.properties");
CqlSessionBuilder builder = CqlSession.builder();
builder.withConfigLoader(DriverConfigLoader.fromFile(confFile));
CqlSession session = builder.build();

应用程序属性

...
datastax-java-driver.advanced.auth-provider.class=PlainTextAuthProvider
datastax-java-driver.advanced.auth-provider.username=${CASSANDRA_USR}
datastax-java-driver.advanced.auth-provider.password=${CASSANDRA_PWD}
datastax-java-driver.advanced.protocol.version=V4
...