lower version, for example 2.6.8
```properties
dubbo.provider.version=1.0
```

2.7.6 failed to recognize the provider url with 'default.version=1.0' key,  it only takes 'version.1.0' into consideration.

return "";
        }
        try {
            return URLDecoder.decode(value, "UTF-8");
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException(e.getMessage(), e);
        }
    }
    static String appendDefaultPort(String address, int defaultPort) {
        if (address != null && address.length() > 0 && defaultPort > 0) {
            int i = address.indexOf(':');
            if (i < 0) {
                return address + ":" + defaultPort;
            } else if (Integer.parseInt(address.substring(i + 1)) == 0) {
                return address.substring(0, i + 1) + defaultPort;
            }
        }
        return address;
    }
    public String getProtocol() {
        return protocol;
    }
    public URL setProtocol(String protocol) {
        return new URL(protocol, username, password, host, port, path, getParameters());
    }
    public String getUsername() {
        return username;
    }
    public URL setUsername(String username) {
        return new URL(protocol, username, password, host, port, path, getParameters());