I've implemented Digicert's SSL using a .p7b cert with Tomcat 9.
You need to generate a keystore file .jks and use that file to configure Tomcat.
Detailed steps can be found here https://www.digicert.com/kb/csr-ssl-installation/tomcat-keytool.htm
My Tomcat 9 C:\AwareIM\Tomcat\conf\server.xml SSL config:
<Connector port="8080" protocol="org.apache.coyote.http11.Http11Nio2Protocol"
connectionTimeout="60000"
redirectPort="8443" />
<Connector port="8443" protocol="org.apache.coyote.http11.Http11Nio2Protocol"
sslImplementationName="org.apache.tomcat.util.net.jsse.JSSEImplementation"
connectionTimeout="20000"
asyncTimeout="150000"
maxThreads="450"
minSpareThreads="50"
SSLEnabled="true"
enableLookups="false"
scheme="https"
secure="true"
maxTrailerSize="-1"
maxCookieCount="-1"
processorCache="450" >
<SSLHostConfig
sslProtocol="TLS"
protocols="+TLSv1,+TLSv1.1,+TLSv1.2,+TLSv1.3,-SSLv2,-SSLv3"
honorCipherOrder="true"
ciphers="TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_DHE_DSS_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_128_SHA256,TLS_ECDHE_ECDSA_WITH_AES_128_SHA256,TLS_ECDHE_RSA_WITH_AES_128_SHA,TLS_ECDHE_ECDSA_WITH_AES_128_SHA,TLS_ECDHE_RSA_WITH_AES_256_SHA384,TLS_ECDHE_ECDSA_WITH_AES_256_SHA384,TLS_ECDHE_RSA_WITH_AES_256_SHA,TLS_ECDHE_ECDSA_WITH_AES_256_SHA,TLS_DHE_RSA_WITH_AES_128_SHA256,TLS_DHE_RSA_WITH_AES_128_SHA,TLS_DHE_DSS_WITH_AES_128_SHA256,TLS_DHE_RSA_WITH_AES_256_SHA256,TLS_DHE_DSS_WITH_AES_256_SHA,TLS_DHE_RSA_WITH_AES_256_SHA" >
<Certificate
certificateKeystoreFile="C:\Your\JKS\File\Location\yourJKSfile.jks"
certificateKeystorePassword="yourPasswordgoesHere"
type="RSA"
certificateKeystoreType="JKS" />
</SSLHostConfig>
</Connector>