Allow the tomcat maxHttpHeaderSize to be changed in external config

Prevents large SPNEGO headers from causing server errors for example.
Added the property to ServerProperties.

Fixes gh-931

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

@@ -27,6 +27,7 @@ import org.apache.catalina.valves.AccessLogValve;
 import org.apache.catalina.valves.RemoteIpValve;
 import org.apache.coyote.AbstractProtocol;
 import org.apache.coyote.ProtocolHandler;
+import org.apache.coyote.http11.AbstractHttp11Protocol;
 import org.springframework.boot.context.embedded.ConfigurableEmbeddedServletContainer;
 import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizer;
 import org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizerBeanPostProcessor;
@@ -41,7 +42,7 @@ import org.springframework.util.StringUtils;
  * {@link ConfigurationProperties properties} for a web server (e.g. port and path
  * settings). Will be used to customize an {@link EmbeddedServletContainerFactory} when an
  * {@link EmbeddedServletContainerCustomizerBeanPostProcessor} is active.
- * 
+ *
  * @author Dave Syer
  * @author Stephane Nicoll
  */
@@ -145,6 +146,8 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer {
 
 		private int maxThreads = 0; // Number of threads in protocol handler
 
+		private int maxHttpHeaderSize = 0; // bytes
+
 		private String uriEncoding;
 
 		public int getMaxThreads() {
@@ -155,6 +158,14 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer {
 			this.maxThreads = maxThreads;
 		}
 
+		public int getMaxHttpHeaderSize() {
+			return maxHttpHeaderSize;
+		}
+
+		public void setMaxHttpHeaderSize(int maxHttpHeaderSize) {
+			this.maxHttpHeaderSize = maxHttpHeaderSize;
+		}
+
 		public boolean getAccessLogEnabled() {
 			return this.accessLogEnabled;
 		}
@@ -246,6 +257,19 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer {
 				});
 			}
 
+			if (this.maxHttpHeaderSize > 0) {
+				factory.addConnectorCustomizers(new TomcatConnectorCustomizer() {
+					@Override
+					public void customize(Connector connector) {
+						ProtocolHandler handler = connector.getProtocolHandler();
+						if (handler instanceof AbstractHttp11Protocol) {
+							AbstractHttp11Protocol protocol = (AbstractHttp11Protocol) handler;
+							protocol.setMaxHttpHeaderSize(Tomcat.this.maxHttpHeaderSize);
+						}
+					}
+				});
+			}
+
 			if (this.accessLogEnabled) {
 				AccessLogValve valve = new AccessLogValve();
 				String accessLogPattern = getAccessLogPattern();

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

@@ -34,7 +34,7 @@ import static org.mockito.Mockito.verify;
 
 /**
  * Tests for {@link ServerProperties}.
- * 
+ *
  * @author Dave Syer
  * @author Stephane Nicoll
  */
@@ -97,4 +97,13 @@ public class ServerPropertiesTests {
 		assertEquals("US-ASCII", this.properties.getTomcat().getUriEncoding());
 	}
 
+	@Test
+    public void testCustomizeTomcatHeaderSize() throws Exception {
+		Map<String, String> map = new HashMap<String, String>();
+		map.put("server.tomcat.maxHttpHeaderSize", "9999");
+		new RelaxedDataBinder(this.properties, "server").bind(new MutablePropertyValues(
+				map));
+		assertEquals(9999, this.properties.getTomcat().getMaxHttpHeaderSize());
+	}
+
 }