Does Spring Boot support Server Name Indication (SNI)?

Does Spring Boot support Server Name Indication (SNI)? Specifically, is it possible for a Spring Boot (2.2.2.RELEASE) application running an embedded Tomcat server and packaged as an executable jar file to support multiple SSL certificates/domains based on the hostname of the incoming request?

It appears [Tomcat supports SNI](https://dzone.com/articles/sni-in-tomcat "SNI in Tomcat") (as of Tomcat 8.5), but I'm not sure how to implement SNI in my Spring Boot app.

I was able to verify that Spring Boot running an embedded Tomcat server supports Server Name Indication (SNI) using the following config:

application.properties

abc.com.key-store=${user.dir}/abc.com.p12
xyz.com.key-store=${user.dir}/xyz.com.p12

ApplicationConfig.java

import org.apache.catalina.connector.Connector;
import org.apache.tomcat.util.net.SSLHostConfig;
import org.apache.tomcat.util.net.SSLHostConfigCertificate;
import org.apache.tomcat.util.net.SSLHostConfigCertificate.Type;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.web.embedded.tomcat.TomcatServletWebServerFactory;
import org.springframework.boot.web.servlet.server.ServletWebServerFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.Environment;

@Configuration
public class ApplicationConfig {
	
	@Autowired
	private Environment env;

	@Bean
	public ServletWebServerFactory servletContainer() throws Exception {

		TomcatServletWebServerFactory tomcat = new TomcatServletWebServerFactory() {
			// Override TomcatServletWebServerFactory methods (if needed)
	    };
	    
	    // add SSL Connector
	    tomcat.addAdditionalTomcatConnectors(createSSLConnectorForMultipleHosts());
	    
	    return tomcat;
	}
	

	private Connector createSSLConnectorForMultipleHosts() {
	    Connector connector = new Connector("org.apache.coyote.http11.Http11NioProtocol");

	    /**
	     * Tomcat 9.0.x server SSL Connector for multiple hosts
	     * 
	    <Connector port="8443" protocol="org.apache.coyote.http11.Http11NioProtocol"
	               maxThreads="150" SSLEnabled="true"
				   defaultSSLHostConfigName="*.abc.com">
	        <SSLHostConfig hostName="*.abc.com">
	            <Certificate certificateKeystoreFile="conf/abc.com.p12"
	                         type="RSA" />
	        </SSLHostConfig>
	        <SSLHostConfig hostName="*.xyz.com">
	            <Certificate certificateKeystoreFile="conf/xyz.com.p12"
	                         type="RSA" />
	        </SSLHostConfig>
	    </Connector>
	     */
	    
	    try {
	    	connector.setScheme("https");
	        connector.setSecure(true);
	        connector.setPort(8443);
		    connector.setAttribute("SSLEnabled", "true");
		    connector.setAttribute("defaultSSLHostConfigName", "*.abc.com");
	        
		    // *.abc.com
	        SSLHostConfig sslHostConfig = new SSLHostConfig();
		    sslHostConfig.setHostName("*.abc.com");
	        
			SSLHostConfigCertificate sslHostConfigCertificate = new SSLHostConfigCertificate(sslHostConfig, Type.RSA);
			sslHostConfigCertificate.setCertificateKeystoreFile(env.getProperty("abc.com.key-store"));
			
			sslHostConfig.addCertificate(sslHostConfigCertificate);
	        connector.addSslHostConfig(sslHostConfig);

		    // *.xyz.com
	        sslHostConfig = new SSLHostConfig();
		    sslHostConfig.setHostName("*.xyz.com");
	        
			sslHostConfigCertificate = new SSLHostConfigCertificate(sslHostConfig, Type.RSA);
			sslHostConfigCertificate.setCertificateKeystoreFile(env.getProperty("xyz.com.key-store"));
			
			sslHostConfig.addCertificate(sslHostConfigCertificate);
	        connector.addSslHostConfig(sslHostConfig);

	        return connector;
	    }
	    catch (Exception ex) {
	        throw new IllegalStateException("Exception creating SSL Connector: ", ex);
	    }
	}

}

Spring supports tomcat connector configuration. I did not run this code but this will give you some idea. You can try something like this:

@Bean
public ServletWebServerFactory servletContainer() throws Exception {
    TomcatServletWebServerFactory tomcat = new TomcatServletWebServerFactory();
    tomcat.addAdditionalTomcatConnectors(createConnector());
    return tomcat;
}

public Connector createConnector() {
    Connector connector = new Connector("org.apache.coyote.http11.Http11AprProtocol");
    connector.setScheme("https");
    connector.setSecure(true);
    connector.setPort(8443);
    connector.addSslHostConfig(getSSLHostConfig());
    return connector;
}

private SSLHostConfig getSSLHostConfig() {
    SSLHostConfig sslHostConfig = new SSLHostConfig();
    sslHostConfig.setHostName("abc.com");
    sslHostConfig.setCertificateFile("abc.crt");
    sslHostConfig.setCaCertificateFile("xyz.crt");
    return sslHostConfig;
}