public synchronized Service secure(String keystoreFile,
                                       String keystorePassword,
                                       String truststoreFile,
                                       String truststorePassword,
                                       boolean needsClientCert) {
        return secure(keystoreFile, keystorePassword, null, truststoreFile, truststorePassword, needsClientCert);
    }
Set the connection to be secure, using the specified keystore and
truststore. This has to be called before any route mapping is done. You
have to supply a keystore file, truststore file is optional (keystore
will be reused).
This method is only relevant when using embedded Jetty servers. It should
not be used if you are using Servlets, where you will need to secure the
connection in the servlet container

@param keystoreFile       The keystore file location as string
@param keystorePassword   the password for the keystore
@param truststoreFile     the truststore file location as string, leave null to reuse
                          keystore
@param needsClientCert    Whether to require client certificate to be supplied in
                          request
@param truststorePassword the trust store password
@return the object with connection set to be secure
src/main/java/spark/Service.java