Document Tomcat compression and GzipFilter auto-configuration

Closes gh-2031

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -74,6 +74,8 @@ content into your application; rather pick only the properties that you need.
 	server.ssl.trust-store-type=
 	server.tomcat.access-log-pattern= # log pattern of the access log
 	server.tomcat.access-log-enabled=false # is access logging enabled
+	server.tomcat.compression=off # is compression enabled (off, on, or an integer content length limit)
+	server.tomcat.compressableMimeTypes=text/html,text/xml,text/plain # comma-separated list of mime types that Tomcat will compress
 	server.tomcat.internal-proxies=10\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}|\\
 			192\\.168\\.\\d{1,3}\\.\\d{1,3}|\\
 			169\\.254\\.\\d{1,3}\\.\\d{1,3}|\\
@@ -105,6 +107,19 @@ content into your application; rather pick only the properties that you need.
 	spring.http.encoding.enabled=true # enable http encoding support
 	spring.http.encoding.force=true # force the configured encoding
 
+	# HTTP response compression ({sc-spring-boot-autoconfigure/web/GzipFilterProperties.{sc-ext}[GzipFilterProperties])
+	spring.http.gzip.bufferSize= # size of the output buffer in bytes
+	spring.http.gzip.minGzipSize= # minimum content length required for compression to occur
+	spring.http.gzip.deflateCompressionLevel= # the level used for deflate compression (0-9)
+	spring.http.gzip.deflateNoWrap= # noWrap setting for deflate compression (true or false)
+	spring.http.gzip.methods= # comma-separated list of HTTP methods for which compression is enabled
+	spring.http.gzip.mimeTypes= # comma-separated list of MIME types which should be compressed
+	spring.http.gzip.excludedAgents= # comma-separated list of user agents to exclude from compression
+	spring.http.gzip.excludedAgentPatterns= # comma-separated list of regular expression patterns to control user agents excluded from compression
+	spring.http.gzip.excludedPaths= # comma-separated list of paths to exclude from compression
+	spring.http.gzip.excludedPathPatterns= # comma-separated list of regular expression patterns to control the paths that are excluded from compression
+	spring.http.gzip.vary= # Vary header to be sent on responses that may be compressed
+
 	# JACKSON ({sc-spring-boot-autoconfigure}}/jackson/JacksonProperties.{sc-ext}[JacksonProperties])
 	spring.jackson.date-format= # Date format string (e.g. yyyy-MM-dd HH:mm:ss), or a fully-qualified date format class name (e.g. com.fasterxml.jackson.databind.util.ISO8601DateFormat)
 	spring.jackson.property-naming-strategy= # One of the constants on Jackson's PropertyNamingStrategy (e.g. CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES) or the fully-qualified class name of a PropertyNamingStrategy subclass

spring-boot-docs/src/main/asciidoc/howto.adoc

@@ -740,6 +740,58 @@ not required.
 
 
 
+[[how-to-enable-http-response-compression]]
+=== Enable HTTP response compression
+Spring Boot provides two mechanisms for enabling compression of HTTP compression; one
+that is Tomcat-specific and another that uses a filter and works with Jetty, Tomcat,
+and Undertow.
+
+
+
+[[how-to-enable-http-response-compression-tomcat]]
+==== Enable Tomcat's HTTP response compression
+Tomcat provides built-in support for HTTP response compression. It is disabled by
+default, but can easily be enabled via `application.properties`:
+
+[source,properties,indent=0,subs="verbatim,quotes,attributes"]
+----
+	server.tomcat.compression: on
+----
+
+When set to `on` Tomcat will compress responses with a length that is at least 2048
+bytes. This limit can be configured by specifying an integer value rather than `on`,
+e.g.:
+
+[source,properties,indent=0,subs="verbatim,quotes,attributes"]
+----
+	server.tomcat.compression: 4096
+----
+
+By default Tomcat will only compress responses with certain MIME types
+(`text/html`, `text/xml`, and `text/plain`). You can customize this using the
+`server.tomcat.compressableMimeTypes` property, e.g.:
+
+[source,properties,indent=0,subs="verbatim,quotes,attributes"]
+----
+	server.tomcat.compressableMimeTypes=application/json,application/xml
+----
+
+
+
+[[how-to-enable-http-compression-gzip-filter]]
+==== Enable HTTP response compression using GzipFilter
+If you're using Jetty or Undertow, or you want more sophisticated control over
+HTTP response compression, Spring Boot provides auto-configuration for Jetty's
+`GzipFilter`. While this filter is part of Jetty, it's compatible with Tomcat
+and Undertow as well. To enable the filter, simply add a dependency on
+`org.eclipse.jetty:jetty-servlets` to your application.
+
+`GzipFilter` can be configured using the `spring.http.gzip.*` properties. See
+{sc-spring-boot-autoconfigure}/web/GzipFilterProperties.{sc-ext}[`GzipFilterProperties`]
+for more details.
+
+
+
 [[howto-spring-mvc]]
 == Spring MVC