Add support for configuring Tomcat’s gzip support using the environment

Tomcat provide built-it support for gzip compression of HTTP responses.
This commit adds support for enabling and configuring this compression
via the environment using server.tomcat.compression and
server.tomcat.compressableMimeTypes.

See gh-2031

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/ServerProperties.java

 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -307,6 +307,19 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer, Ord
 		 */
 		private String uriEncoding;
 
+		/**
+		 * Controls response compression. Acceptable values are "off" to disable
+		 * compression, "on" to enable compression of responses over 2048 bytes, "force"
+		 * to force response compression, or an integer value to enable compression of
+		 * responses with content length that is at least that value.
+		 */
+		private String compression = "off";
+
+		/**
+		 * A comma-separated list of MIME types for which compression is used.
+		 */
+		private String compressableMimeTypes = "text/html,text/xml,text/plain";
+
 		public int getMaxThreads() {
 			return this.maxThreads;
 		}
@@ -355,6 +368,22 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer, Ord
 			this.accessLogPattern = accessLogPattern;
 		}
 
+		public String getCompressableMimeTypes() {
+			return this.compressableMimeTypes;
+		}
+
+		public void setCompressableMimeTypes(String compressableMimeTypes) {
+			this.compressableMimeTypes = compressableMimeTypes;
+		}
+
+		public String getCompression() {
+			return this.compression;
+		}
+
+		public void setCompression(String compression) {
+			this.compression = compression;
+		}
+
 		public String getInternalProxies() {
 			return this.internalProxies;
 		}
@@ -447,6 +476,19 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer, Ord
 				});
 			}
 
+			factory.addConnectorCustomizers(new TomcatConnectorCustomizer() {
+				@Override
+				public void customize(Connector connector) {
+					ProtocolHandler handler = connector.getProtocolHandler();
+					if (handler instanceof AbstractHttp11Protocol) {
+						@SuppressWarnings("rawtypes")
+						AbstractHttp11Protocol protocol = (AbstractHttp11Protocol) handler;
+						protocol.setCompression(Tomcat.this.compression);
+						protocol.setCompressableMimeTypes(Tomcat.this.compressableMimeTypes);
+					}
+				}
+			});
+
 			if (this.accessLogEnabled) {
 				AccessLogValve valve = new AccessLogValve();
 				String accessLogPattern = getAccessLogPattern();

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/ServerPropertiesTests.java

 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,10 +23,12 @@ import java.util.Map;
 
 import org.apache.catalina.Valve;
 import org.apache.catalina.valves.RemoteIpValve;
+import org.apache.coyote.http11.AbstractHttp11Protocol;
 import org.junit.Test;
 import org.springframework.beans.MutablePropertyValues;
 import org.springframework.boot.bind.RelaxedDataBinder;
 import org.springframework.boot.context.embedded.ConfigurableEmbeddedServletContainer;
+import org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainer;
 import org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory;
 
 import static org.hamcrest.core.IsInstanceOf.instanceOf;
@@ -193,6 +195,52 @@ public class ServerPropertiesTests {
 		assertEquals("192.168.0.1", remoteIpValve.getInternalProxies());
 	}
 
+	@Test
+	public void customTomcatCompression() throws Exception {
+		Map<String, String> map = new HashMap<String, String>();
+		map.put("server.port", "0");
+		map.put("server.tomcat.compression", "on");
+		bindProperties(map);
+
+		TomcatEmbeddedServletContainerFactory factory = new TomcatEmbeddedServletContainerFactory();
+		this.properties.customize(factory);
+
+		TomcatEmbeddedServletContainer container = (TomcatEmbeddedServletContainer) factory
+				.getEmbeddedServletContainer();
+
+		try {
+			AbstractHttp11Protocol<?> protocol = (AbstractHttp11Protocol<?>) container
+					.getTomcat().getConnector().getProtocolHandler();
+			assertEquals("on", protocol.getCompression());
+		}
+		finally {
+			container.stop();
+		}
+	}
+
+	@Test
+	public void customTomcatCompressableMimeTypes() throws Exception {
+		Map<String, String> map = new HashMap<String, String>();
+		map.put("server.port", "0");
+		map.put("server.tomcat.compressableMimeTypes", "application/foo");
+		bindProperties(map);
+
+		TomcatEmbeddedServletContainerFactory factory = new TomcatEmbeddedServletContainerFactory();
+		this.properties.customize(factory);
+
+		TomcatEmbeddedServletContainer container = (TomcatEmbeddedServletContainer) factory
+				.getEmbeddedServletContainer();
+
+		try {
+			AbstractHttp11Protocol<?> protocol = (AbstractHttp11Protocol<?>) container
+					.getTomcat().getConnector().getProtocolHandler();
+			assertEquals("application/foo", protocol.getCompressableMimeTypes());
+		}
+		finally {
+			container.stop();
+		}
+	}
+
 	private void bindProperties(Map<String, String> map) {
 		new RelaxedDataBinder(this.properties, "server").bind(new MutablePropertyValues(
 				map));