* The client implementation is determined by the system property.
     */
    public SwitchableHttpClient() {
        super();
        selectClient();
    }

    /**
     * Selects the appropriate HTTP client based on system property.
     */
    protected void selectClient() {
        final String clientType = System.getProperty(HTTP_CLIENT_PROPERTY);
        if (HC4_CLIENT.equalsIgnoreCase(clientType)) {