private static KeyStore createEmptyKeyStore() throws GeneralSecurityException, IOException {
    return createEmptyKeyStore("jks");
  }
Create a self-signed X.509 Certificate.
@param dn        the X.509 Distinguished Name, eg "CN=Test, L=London, C=GB"
@param pair      the KeyPair
@param days      how many days from now the Certificate is valid for
@param algorithm the signing algorithm, eg "SHA1withRSA"
@return the self-signed certificate
hbase-http/src/test/java/org/apache/hadoop/hbase/http/ssl/KeyStoreTestUtil.java