apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/spi/springsecurity/PasswordEncoderAdapter.java/PasswordEncoderAdapter/extractId
class PasswordEncoderAdapter:  private String extractId(String prefixEncodedPassword) {
    if (prefixEncodedPassword == null) {
      return null;
    }
    int start = prefixEncodedPassword.indexOf(PREFIX);
    if (start != 0) {
      return null;
    }
    int end = prefixEncodedPassword.indexOf(SUFFIX, start);
    if (end < 0) {
      return null;
    }
    return prefixEncodedPassword.substring(start + 1, end);
  }