Make WebMvcMetricsFilter lazy

Update `WebMvcMetricsFilter` so that it no longer causes early
initialization of Spring MVC concerns.

Fixes gh-11571

Author: philwebb

Diff for: spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/web/servlet/WebMvcMetricsConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -27,10 +27,10 @@
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.web.servlet.DispatcherServlet;
-import org.springframework.web.servlet.handler.HandlerMappingIntrospector;
 
 /**
  * Configures instrumentation of Spring Web MVC servlet-based request mappings.
@@ -60,9 +60,8 @@ public WebMvcMetrics controllerMetrics(MeterRegistry registry,
 	}
 
 	@Bean
-	public WebMvcMetricsFilter webMetricsFilter(WebMvcMetrics controllerMetrics,
-			HandlerMappingIntrospector introspector) {
-		return new WebMvcMetricsFilter(controllerMetrics, introspector);
+	public WebMvcMetricsFilter webMetricsFilter(ApplicationContext context) {
+		return new WebMvcMetricsFilter(context);
 	}
 
 }

Diff for: spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/web/servlet/WebMvcMetricsFilter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -26,6 +26,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import org.springframework.context.ApplicationContext;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
 import org.springframework.web.filter.OncePerRequestFilter;
@@ -47,14 +48,14 @@ public class WebMvcMetricsFilter extends OncePerRequestFilter {
 	private static final Logger logger = LoggerFactory
 			.getLogger(WebMvcMetricsFilter.class);
 
-	private final WebMvcMetrics webMvcMetrics;
+	private final ApplicationContext context;
 
-	private final HandlerMappingIntrospector mappingIntrospector;
+	private volatile WebMvcMetrics webMvcMetrics;
 
-	public WebMvcMetricsFilter(WebMvcMetrics webMvcMetrics,
-			HandlerMappingIntrospector mappingIntrospector) {
-		this.webMvcMetrics = webMvcMetrics;
-		this.mappingIntrospector = mappingIntrospector;
+	private volatile HandlerMappingIntrospector mappingIntrospector;
+
+	public WebMvcMetricsFilter(ApplicationContext context) {
+		this.context = context;
 	}
 
 	@Override
@@ -74,7 +75,7 @@ protected void doFilterInternal(HttpServletRequest request,
 
 	private HandlerExecutionChain getHandlerExecutionChain(HttpServletRequest request) {
 		try {
-			MatchableHandlerMapping matchableHandlerMapping = this.mappingIntrospector
+			MatchableHandlerMapping matchableHandlerMapping = getMappingIntrospector()
 					.getMatchableHandlerMapping(request);
 			return (matchableHandlerMapping == null ? null
 					: matchableHandlerMapping.getHandler(request));
@@ -90,19 +91,35 @@ private HandlerExecutionChain getHandlerExecutionChain(HttpServletRequest reques
 	private void filterWithMetrics(HttpServletRequest request,
 			HttpServletResponse response, FilterChain filterChain, Object handler)
 					throws IOException, ServletException {
-		this.webMvcMetrics.preHandle(request, handler);
+		WebMvcMetrics metrics = getWebMvcMetrics();
+		metrics.preHandle(request, handler);
 		try {
 			filterChain.doFilter(request, response);
 			// When an async operation is complete, the whole filter gets called again
 			// with isAsyncStarted = false
 			if (!request.isAsyncStarted()) {
-				this.webMvcMetrics.record(request, response, null);
+				metrics.record(request, response, null);
 			}
 		}
 		catch (NestedServletException ex) {
-			this.webMvcMetrics.record(request, response, ex.getCause());
+			metrics.record(request, response, ex.getCause());
 			throw ex;
 		}
 	}
 
+	private HandlerMappingIntrospector getMappingIntrospector() {
+		if (this.mappingIntrospector == null) {
+			this.mappingIntrospector = this.context
+					.getBean(HandlerMappingIntrospector.class);
+		}
+		return this.mappingIntrospector;
+	}
+
+	private WebMvcMetrics getWebMvcMetrics() {
+		if (this.webMvcMetrics == null) {
+			this.webMvcMetrics = this.context.getBean(WebMvcMetrics.class);
+		}
+		return this.webMvcMetrics;
+	}
+
 }

Diff for: spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/web/servlet/WebMvcMetricsFilterAutoTimedTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -26,6 +26,7 @@
 import org.junit.runner.RunWith;
 
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
@@ -39,7 +40,6 @@
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.context.WebApplicationContext;
 import org.springframework.web.servlet.config.annotation.EnableWebMvc;
-import org.springframework.web.servlet.handler.HandlerMappingIntrospector;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
@@ -104,9 +104,8 @@ public WebMvcMetrics controllerMetrics(MeterRegistry registry) {
 		}
 
 		@Bean
-		public WebMvcMetricsFilter webMetricsFilter(WebMvcMetrics controllerMetrics,
-				HandlerMappingIntrospector introspector) {
-			return new WebMvcMetricsFilter(controllerMetrics, introspector);
+		public WebMvcMetricsFilter webMetricsFilter(ApplicationContext context) {
+			return new WebMvcMetricsFilter(context);
 		}
 
 	}

Diff for: spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/web/servlet/WebMvcMetricsFilterTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -39,6 +39,7 @@
 import org.junit.runner.RunWith;
 
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
@@ -58,7 +59,6 @@
 import org.springframework.web.filter.OncePerRequestFilter;
 import org.springframework.web.servlet.ModelAndView;
 import org.springframework.web.servlet.config.annotation.EnableWebMvc;
-import org.springframework.web.servlet.handler.HandlerMappingIntrospector;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatCode;
@@ -237,9 +237,8 @@ public WebMvcMetrics controllerMetrics(MeterRegistry registry) {
 		}
 
 		@Bean
-		public WebMvcMetricsFilter webMetricsFilter(WebMvcMetrics controllerMetrics,
-				HandlerMappingIntrospector introspector) {
-			return new WebMvcMetricsFilter(controllerMetrics, introspector);
+		public WebMvcMetricsFilter webMetricsFilter(ApplicationContext context) {
+			return new WebMvcMetricsFilter(context);
 		}
 
 	}

Diff for: spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/web/servlet/WebMvcMetricsIntegrationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -28,6 +28,7 @@
 import org.junit.runner.RunWith;
 
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.http.HttpStatus;
@@ -43,7 +44,6 @@
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.context.WebApplicationContext;
 import org.springframework.web.servlet.config.annotation.EnableWebMvc;
-import org.springframework.web.servlet.handler.HandlerMappingIntrospector;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatCode;
@@ -119,9 +119,8 @@ public WebMvcMetrics controllerMetrics(MeterRegistry registry) {
 		}
 
 		@Bean
-		public WebMvcMetricsFilter webMetricsFilter(WebMvcMetrics controllerMetrics,
-				HandlerMappingIntrospector introspector) {
-			return new WebMvcMetricsFilter(controllerMetrics, introspector);
+		public WebMvcMetricsFilter webMetricsFilter(ApplicationContext context) {
+			return new WebMvcMetricsFilter(context);
 		}
 
 		@RestController