@Override
    public String toString() {
        return "RegistryConfig{" +
            "protocol='" + protocol + '\'' +
            ", address='" + address + '\'' +
            ", index='" + index + '\'' +
            ", register=" + register +
            ", subscribe=" + subscribe +
            ", timeout=" + timeout +
            ", connectTimeout=" + connectTimeout +
            ", file='" + file + '\'' +
            ", batch=" + batch +
            ", batchSize=" + batchSize +
            ", heartbeatPeriod=" + heartbeatPeriod +
            ", reconnectPeriod=" + reconnectPeriod +
            ", parameters=" + parameters +
            '}';
    }
Gets parameter or default.

@param key the key
@return the value
core/api/src/main/java/com/alipay/sofa/rpc/config/RegistryConfig.java