Fix FailureAnalyzers tangle

Create a new `SpringBootExceptionReporter` interface so that a direct
link between `SpringApplication` and `FailureAnalyzers` is no longer
needed.

This prevents package tangle warnings and allows for cleaner separation
of concerns.

Fixes gh-8612

spring-boot/src/main/java/org/springframework/boot/SpringApplication.java

@@ -42,7 +42,6 @@ import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
 import org.springframework.boot.Banner.Mode;
 import org.springframework.boot.bind.PropertiesConfigurationFactory;
 import org.springframework.boot.bind.RelaxedPropertyResolver;
-import org.springframework.boot.diagnostics.FailureAnalyzers;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextInitializer;
 import org.springframework.context.ApplicationListener;
@@ -328,7 +327,7 @@ public class SpringApplication {
 		StopWatch stopWatch = new StopWatch();
 		stopWatch.start();
 		ConfigurableApplicationContext context = null;
-		FailureAnalyzers analyzers = null;
+		Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
 		configureHeadlessProperty();
 		SpringApplicationRunListeners listeners = getRunListeners(args);
 		listeners.starting();
@@ -341,7 +340,8 @@ public class SpringApplication {
 			bindToSpringApplication(environment);
 			Banner printedBanner = printBanner(environment);
 			context = createApplicationContext();
-			analyzers = new FailureAnalyzers(context);
+			exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
+					new Class[] { ConfigurableApplicationContext.class }, context);
 			prepareContext(context, environment, listeners, applicationArguments,
 					printedBanner);
 			refreshContext(context);
@@ -355,7 +355,7 @@ public class SpringApplication {
 			return context;
 		}
 		catch (Throwable ex) {
-			handleRunFailure(context, listeners, analyzers, ex);
+			handleRunFailure(context, listeners, exceptionReporters, ex);
 			throw new IllegalStateException(ex);
 		}
 	}
@@ -423,11 +423,11 @@ public class SpringApplication {
 				SpringApplicationRunListener.class, types, this, args));
 	}
 
-	private <T> Collection<? extends T> getSpringFactoriesInstances(Class<T> type) {
+	private <T> Collection<T> getSpringFactoriesInstances(Class<T> type) {
 		return getSpringFactoriesInstances(type, new Class<?>[] {});
 	}
 
-	private <T> Collection<? extends T> getSpringFactoriesInstances(Class<T> type,
+	private <T> Collection<T> getSpringFactoriesInstances(Class<T> type,
 			Class<?>[] parameterTypes, Object... args) {
 		ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
 		// Use names and ensure unique to protect against duplicates
@@ -853,15 +853,15 @@ public class SpringApplication {
 	}
 
 	private void handleRunFailure(ConfigurableApplicationContext context,
-			SpringApplicationRunListeners listeners, FailureAnalyzers analyzers,
-			Throwable exception) {
+			SpringApplicationRunListeners listeners,
+			Collection<SpringBootExceptionReporter> exceptionReporters, Throwable exception) {
 		try {
 			try {
 				handleExitCode(context, exception);
 				listeners.finished(context, exception);
 			}
 			finally {
-				reportFailure(analyzers, exception);
+				reportFailure(exceptionReporters, exception);
 				if (context != null) {
 					context.close();
 				}
@@ -873,11 +873,14 @@ public class SpringApplication {
 		ReflectionUtils.rethrowRuntimeException(exception);
 	}
 
-	private void reportFailure(FailureAnalyzers analyzers, Throwable failure) {
+	private void reportFailure(Collection<SpringBootExceptionReporter> exceptionReporters,
+			Throwable failure) {
 		try {
-			if (analyzers != null && analyzers.analyzeAndReport(failure)) {
-				registerLoggedException(failure);
-				return;
+			for (SpringBootExceptionReporter reporter : exceptionReporters) {
+				if (reporter.reportException(failure)) {
+					registerLoggedException(failure);
+					return;
+				}
 			}
 		}
 		catch (Throwable ex) {

spring-boot/src/main/java/org/springframework/boot/SpringBootExceptionReporter.java

+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot;
+
+import org.springframework.context.ApplicationContextAware;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.core.io.support.SpringFactoriesLoader;
+
+/**
+ * Callback interface used to support custom reporting of {@link SpringApplication}
+ * startup errors. {@link SpringBootExceptionReporter reporters} are loaded via the
+ * {@link SpringFactoriesLoader} and must declare a public constructor with a single
+ * {@link ConfigurableApplicationContext} parameter.
+ *
+ * @author Phillip Webb
+ * @since 2.0.0
+ * @see ApplicationContextAware
+ */
+public interface SpringBootExceptionReporter {
+
+	/**
+	 * Report a startup failure to the user.
+	 * @param failure the source failure
+	 * @return {@code true} if the failure was reported or {@code false} if default
+	 * reporting should occur.
+	 */
+	boolean reportException(Throwable failure);
+
+}

spring-boot/src/main/java/org/springframework/boot/diagnostics/FailureAnalyzers.java

@@ -25,6 +25,7 @@ import org.apache.commons.logging.LogFactory;
 
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
+import org.springframework.boot.SpringBootExceptionReporter;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
 import org.springframework.core.io.support.SpringFactoriesLoader;
@@ -44,9 +45,8 @@ import org.springframework.util.ReflectionUtils;
  * @author Andy Wilkinson
  * @author Phillip Webb
  * @author Stephane Nicoll
- * @since 1.4.0
  */
-public final class FailureAnalyzers {
+final class FailureAnalyzers implements SpringBootExceptionReporter {
 
 	private static final Log logger = LogFactory.getLog(FailureAnalyzers.class);
 
@@ -54,12 +54,7 @@ public final class FailureAnalyzers {
 
 	private final List<FailureAnalyzer> analyzers;
 
-	/**
-	 * Create a new {@link FailureAnalyzers} instance.
-	 * @param context the source application context
-	 * @since 1.4.1
-	 */
-	public FailureAnalyzers(ConfigurableApplicationContext context) {
+	FailureAnalyzers(ConfigurableApplicationContext context) {
 		this(context, null);
 	}
 
@@ -103,12 +98,8 @@ public final class FailureAnalyzers {
 		}
 	}
 
-	/**
-	 * Analyze and report the specified {@code failure}.
-	 * @param failure the failure to analyze
-	 * @return {@code true} if the failure was handled
-	 */
-	public boolean analyzeAndReport(Throwable failure) {
+	@Override
+	public boolean reportException(Throwable failure) {
 		FailureAnalysis analysis = analyze(failure, this.analyzers);
 		return report(analysis, this.classLoader);
 	}

spring-boot/src/main/resources/META-INF/spring.factories

@@ -7,6 +7,10 @@ org.springframework.boot.env.YamlPropertySourceLoader
 org.springframework.boot.SpringApplicationRunListener=\
 org.springframework.boot.context.event.EventPublishingRunListener
 
+# Error Reporters
+org.springframework.boot.SpringBootExceptionReporter=\
+org.springframework.boot.diagnostics.FailureAnalyzers
+
 # Application Context Initializers
 org.springframework.context.ApplicationContextInitializer=\
 org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,\

spring-boot/src/test/java/org/springframework/boot/diagnostics/FailureAnalyzersTests.java

@@ -78,7 +78,7 @@ public class FailureAnalyzersTests {
 	private void analyzeAndReport(String factoriesName, Throwable failure) {
 		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
 		ClassLoader classLoader = new CustomSpringFactoriesClassLoader(factoriesName);
-		new FailureAnalyzers(context, classLoader).analyzeAndReport(failure);
+		new FailureAnalyzers(context, classLoader).reportException(failure);
 	}
 
 	static class BasicFailureAnalyzer implements FailureAnalyzer {