Improve Servlet and Filter registration logging

Prior to this commit, the information logged at DEBUG level for the web
infrastructure was not consistent with the experience in Spring
Framework.

This commit moves some logging information about
`ServletContextInitializer` registrations from DEBUG to TRACE level and
gathers the Servlets and Filters registration logs into one-liners at
the DEBUG level.

Closes gh-15166

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/logging/LoggingApplicationListener.java

@@ -131,6 +131,8 @@ public class LoggingApplicationListener implements GenericApplicationListener {
 		loggers.add("web", "org.springframework.http");
 		loggers.add("web", "org.springframework.web");
 		loggers.add("web", "org.springframework.boot.actuate.endpoint.web");
+		loggers.add("web",
+				"org.springframework.boot.web.servlet.ServletContextInitializerBeans");
 		loggers.add("sql", "org.springframework.jdbc.core");
 		loggers.add("sql", "org.hibernate.SQL");
 		DEFAULT_GROUP_LOGGERS = Collections.unmodifiableMap(loggers);

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/servlet/AbstractFilterRegistrationBean.java

@@ -41,6 +41,7 @@ import org.springframework.util.StringUtils;
  *
  * @param <T> the type of {@link Filter} to register
  * @author Phillip Webb
+ * @author Brian Clozel
  * @since 2.0.1
  */
 public abstract class AbstractFilterRegistrationBean<T extends Filter>
@@ -245,27 +246,38 @@ public abstract class AbstractFilterRegistrationBean<T extends Filter>
 		}
 		servletNames.addAll(this.servletNames);
 		if (servletNames.isEmpty() && this.urlPatterns.isEmpty()) {
-			this.logger.info("Mapping filter: '" + registration.getName() + "' to: "
-					+ Arrays.asList(DEFAULT_URL_MAPPINGS));
 			registration.addMappingForUrlPatterns(dispatcherTypes, this.matchAfter,
 					DEFAULT_URL_MAPPINGS);
 		}
 		else {
 			if (!servletNames.isEmpty()) {
-				this.logger.info("Mapping filter: '" + registration.getName()
-						+ "' to servlets: " + servletNames);
 				registration.addMappingForServletNames(dispatcherTypes, this.matchAfter,
 						StringUtils.toStringArray(servletNames));
 			}
 			if (!this.urlPatterns.isEmpty()) {
-				this.logger.info("Mapping filter: '" + registration.getName()
-						+ "' to urls: " + this.urlPatterns);
 				registration.addMappingForUrlPatterns(dispatcherTypes, this.matchAfter,
 						StringUtils.toStringArray(this.urlPatterns));
 			}
 		}
 	}
 
+	@Override
+	public String toString() {
+		StringBuilder builder = new StringBuilder(getOrDeduceName(this));
+		if (this.servletNames.isEmpty() && this.urlPatterns.isEmpty()) {
+			builder.append(" urls=").append(Arrays.toString(DEFAULT_URL_MAPPINGS));
+		}
+		else {
+			if (!this.servletNames.isEmpty()) {
+				builder.append(" servlets=").append(this.servletNames);
+			}
+			if (!this.urlPatterns.isEmpty()) {
+				builder.append(" urls=").append(this.urlPatterns);
+			}
+		}
+		return builder.toString();
+	}
+
 	/**
 	 * Return the {@link Filter} to be registered.
 	 * @return the filter

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/servlet/ServletContextInitializerBeans.java

@@ -57,6 +57,7 @@ import org.springframework.util.MultiValueMap;
  *
  * @author Dave Syer
  * @author Phillip Webb
+ * @author Brian Clozel
  * @since 1.4.0
  */
 public class ServletContextInitializerBeans
@@ -93,6 +94,7 @@ public class ServletContextInitializerBeans
 						.sorted(AnnotationAwareOrderComparator.INSTANCE))
 				.collect(Collectors.toList());
 		this.sortedList = Collections.unmodifiableList(sortedInitializers);
+		logBeansInformation(this.initializers);
 	}
 
 	private void addServletContextInitializerBeans(ListableBeanFactory beanFactory) {
@@ -143,10 +145,10 @@ public class ServletContextInitializerBeans
 			// Mark the underlying source as seen in case it wraps an existing bean
 			this.seen.add(source);
 		}
-		if (ServletContextInitializerBeans.logger.isDebugEnabled()) {
+		if (ServletContextInitializerBeans.logger.isTraceEnabled()) {
 			String resourceDescription = getResourceDescription(beanName, beanFactory);
 			int order = getOrder(initializer);
-			ServletContextInitializerBeans.logger.debug("Added existing "
+			ServletContextInitializerBeans.logger.trace("Added existing "
 					+ type.getSimpleName() + " initializer bean '" + beanName
 					+ "'; order=" + order + ", resource=" + resourceDescription);
 		}
@@ -200,8 +202,8 @@ public class ServletContextInitializerBeans
 						bean.getValue(), beans.size());
 				registration.setOrder(order);
 				this.initializers.add(type, registration);
-				if (ServletContextInitializerBeans.logger.isDebugEnabled()) {
+				if (ServletContextInitializerBeans.logger.isTraceEnabled()) {
-					ServletContextInitializerBeans.logger.debug(
+					ServletContextInitializerBeans.logger.trace(
 							"Created " + type.getSimpleName() + " initializer for bean '"
 									+ beanName + "'; order=" + order + ", resource="
 									+ getResourceDescription(beanName, beanFactory));
@@ -245,6 +247,36 @@ public class ServletContextInitializerBeans
 		return beans;
 	}
 
+	private void logBeansInformation(
+			MultiValueMap<Class<?>, ServletContextInitializer> initializers) {
+		if (ServletContextInitializerBeans.logger.isDebugEnabled()) {
+			List<ServletContextInitializer> filterRegistrations = new ArrayList<>();
+			filterRegistrations.addAll(initializers
+					.getOrDefault(FilterRegistrationBean.class, Collections.emptyList()));
+			filterRegistrations.addAll(
+					initializers.getOrDefault(Filter.class, Collections.emptyList()));
+			String filtersInfo = filterRegistrations.stream()
+					.map(FilterRegistrationBean.class::cast)
+					.map(FilterRegistrationBean::toString)
+					.collect(Collectors.joining(", "));
+			ServletContextInitializerBeans.logger
+					.debug("Mapping filters: " + filtersInfo);
+
+			List<ServletContextInitializer> servletRegistrations = new ArrayList<>();
+			servletRegistrations.addAll(initializers.getOrDefault(
+					ServletRegistrationBean.class, Collections.emptyList()));
+			servletRegistrations.addAll(
+					initializers.getOrDefault(Servlet.class, Collections.emptyList()));
+			String servletsInfo = servletRegistrations.stream()
+					.map(ServletRegistrationBean.class::cast)
+					.map((servlet) -> servlet.getServletName() + " "
+							+ servlet.getUrlMappings())
+					.collect(Collectors.joining(", "));
+			ServletContextInitializerBeans.logger
+					.debug("Mapping servlets: " + servletsInfo);
+		}
+	}
+
 	@Override
 	public Iterator<ServletContextInitializer> iterator() {
 		return this.sortedList.iterator();

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/servlet/ServletRegistrationBean.java

@@ -183,7 +183,6 @@ public class ServletRegistrationBean<T extends Servlet>
 	protected ServletRegistration.Dynamic addRegistration(String description,
 			ServletContext servletContext) {
 		String name = getServletName();
-		logger.info("Servlet " + name + " mapped to " + this.urlMappings);
 		return servletContext.addServlet(name, this.servlet);
 	}
 

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/logging/LoggingApplicationListenerTests.java

@@ -570,6 +570,9 @@ public class LoggingApplicationListenerTests {
 		assertTraceEnabled("org.springframework.http", true);
 		assertTraceEnabled("org.springframework.web", true);
 		assertTraceEnabled("org.springframework.boot.actuate.endpoint.web", true);
+		assertTraceEnabled(
+				"org.springframework.boot.web.servlet.ServletContextInitializerBeans",
+				true);
 	}
 
 	@Test