Upgrade to Spring Boot 2.2.1.RELEASE.

Author: gregturn

README.adoc

@@ -1,4 +1,4 @@
-:spring_boot_version: 2.1.6.RELEASE
+:spring_boot_version: 2.2.1.RELEASE
 :toc:
 :icons: font
 :source-highlighter: prettify
@@ -157,7 +157,7 @@ Congratulations! You have just used Spring to develop a simple JDBC client.
 
 NOTE: Spring Boot has many features for configuring and customizing the connection pool --
 for instance, to connect to an external database instead of an in-memory one. See the
-http://docs.spring.io/spring-boot/docs/2.1.6.RELEASE/reference/htmlsingle/#boot-features-configure-datasource[Reference Guide]
+http://docs.spring.io/spring-boot/docs/2.2.1.RELEASE/reference/htmlsingle/#boot-features-configure-datasource[Reference Guide]
 for more detail.
 
 == See Also