Detect SpringBootServletInitializer @Configuration

Update SpringBootServletInitializer to automatically add itself as a
SpringApplication source if it is annotated with @Configuration.

Also throw a more meaningful exception if no sources have been
configured.

Fixes gh-2073

spring-boot/src/main/java/org/springframework/boot/builder/SpringApplicationBuilder.java

@@ -120,7 +120,6 @@ public class SpringApplicationBuilder {
 	 * @return an application context created from the current state
 	 */
 	public ConfigurableApplicationContext run(String... args) {
-
 		if (this.parent != null) {
 			// If there is a parent don't register a shutdown hook
 			if (!this.registerShutdownHookApplied) {
@@ -130,22 +129,26 @@ public class SpringApplicationBuilder {
 			initializers(new ParentContextApplicationContextInitializer(
 					this.parent.run(args)));
 		}
-
 		if (this.running.get()) {
 			// If already created we just return the existing context
 			return this.context;
 		}
-
 		if (this.running.compareAndSet(false, true)) {
 			synchronized (this.running) {
 				// If not already running copy the sources over and then run.
-				this.application.setSources(this.sources);
-				this.context = this.application.run(args);
+				this.context = build().run(args);
 			}
 		}
-
 		return this.context;
+	}
 
+	/**
+	 * Returns a fully configured {@link SpringApplication} that is ready to run.
+	 * @return the fully configured {@link SpringApplication}.
+	 */
+	public SpringApplication build() {
+		this.application.setSources(this.sources);
+		return this.application;
 	}
 
 	/**
@@ -155,7 +158,6 @@ public class SpringApplicationBuilder {
 	 * @return the child application builder
 	 */
 	public SpringApplicationBuilder child(Object... sources) {
-
 		SpringApplicationBuilder child = new SpringApplicationBuilder();
 		child.sources(sources);
 
@@ -176,7 +178,6 @@ public class SpringApplicationBuilder {
 		this.application.setSources(this.sources);
 
 		return child;
-
 	}
 
 	/**

spring-boot/src/main/java/org/springframework/boot/context/web/SpringBootServletInitializer.java

@@ -16,31 +16,45 @@
 
 package org.springframework.boot.context.web;
 
+import javax.servlet.Filter;
+import javax.servlet.Servlet;
 import javax.servlet.ServletContext;
 import javax.servlet.ServletContextEvent;
 import javax.servlet.ServletException;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.springframework.boot.SpringApplication;
 import org.springframework.boot.builder.ParentContextApplicationContextInitializer;
 import org.springframework.boot.builder.SpringApplicationBuilder;
 import org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext;
+import org.springframework.boot.context.embedded.ServletContextInitializer;
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.util.Assert;
 import org.springframework.web.WebApplicationInitializer;
 import org.springframework.web.context.ContextLoaderListener;
 import org.springframework.web.context.WebApplicationContext;
 
 /**
- * A handy opinionated {@link WebApplicationInitializer} for applications that starts a
- * Spring Boot application and lets it bind to the servlet and filter mappings. If your
- * application is more complicated consider using one of the other
- * WebApplicationInitializers.
+ * An opinionated {@link WebApplicationInitializer} to run a {@link SpringApplication}
+ * from a traditional WAR deployment. Binds {@link Servlet}, {@link Filter} and
+ * {@link ServletContextInitializer} beans from the application context to the servlet
+ * container.
+ * <p>
+ * To configure the application either override the
+ * {@link #configure(SpringApplicationBuilder)} method (calling
+ * {@link SpringApplicationBuilder#sources(Object...)}) or make the initializer itself a
+ * {@code @Configuration}.
  * <p>
  * Note that a WebApplicationInitializer is only needed if you are building a war file and
- * deploying it. If you prefer to run an embedded container (we do) then you won't need
- * this at all.
+ * deploying it. If you prefer to run an embedded container then you won't need this at
+ * all.
  *
  * @author Dave Syer
+ * @author Phillip Webb
+ * @see #configure(SpringApplicationBuilder)
  */
 public abstract class SpringBootServletInitializer implements WebApplicationInitializer {
 
@@ -66,29 +80,50 @@ public abstract class SpringBootServletInitializer implements WebApplicationInit
 
 	protected WebApplicationContext createRootApplicationContext(
 			ServletContext servletContext) {
-		ApplicationContext parent = null;
-		Object object = servletContext
-				.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
-		if (object instanceof ApplicationContext) {
+		SpringApplicationBuilder builder = new SpringApplicationBuilder();
+		ApplicationContext parent = getExistingRootWebApplicationContext(servletContext);
+		if (parent != null) {
 			this.logger.info("Root context already created (using as parent).");
-			parent = (ApplicationContext) object;
 			servletContext.setAttribute(
 					WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, null);
+			builder.initializers(new ParentContextApplicationContextInitializer(parent));
 		}
-		SpringApplicationBuilder application = new SpringApplicationBuilder();
-		if (parent != null) {
-			application.initializers(new ParentContextApplicationContextInitializer(
-					parent));
-		}
-		application.initializers(new ServletContextApplicationContextInitializer(
+		builder.initializers(new ServletContextApplicationContextInitializer(
 				servletContext));
-		application.contextClass(AnnotationConfigEmbeddedWebApplicationContext.class);
-		application = configure(application);
+		builder.contextClass(AnnotationConfigEmbeddedWebApplicationContext.class);
+		builder = configure(builder);
+		SpringApplication application = builder.build();
+		if (application.getSources().isEmpty()
+				&& AnnotationUtils.findAnnotation(getClass(), Configuration.class) != null) {
+			application.getSources().add(getClass());
+		}
+		Assert.state(application.getSources().size() > 0,
+				"No SpringApplication sources have been defined. Either override the "
+						+ "configure method or add an @Configuration annotation");
 		// Ensure error pages are registered
-		application.sources(ErrorPageFilter.class);
+		application.getSources().add(ErrorPageFilter.class);
+		return run(application);
+	}
+
+	/**
+	 * Called to run a fully configured {@link SpringApplication}.
+	 * @param application the application to run
+	 * @return the {@link WebApplicationContext}
+	 */
+	protected WebApplicationContext run(SpringApplication application) {
 		return (WebApplicationContext) application.run();
 	}
 
+	private ApplicationContext getExistingRootWebApplicationContext(
+			ServletContext servletContext) {
+		Object context = servletContext
+				.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
+		if (context instanceof ApplicationContext) {
+			return (ApplicationContext) context;
+		}
+		return null;
+	}
+
 	/**
 	 * Configure the application. Normally all you would need to do it add sources (e.g.
 	 * config classes) because other settings have sensible defaults. You might choose

spring-boot/src/test/java/org/springframework/boot/context/web/SpringBootServletInitializerTests.java

@@ -0,0 +1,110 @@
+/*
+ * Copyright 2012-2014 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.context.web;
+
+import java.util.LinkedHashSet;
+import java.util.Set;
+
+import javax.servlet.ServletContext;
+
+import org.hamcrest.Matcher;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.mock.web.MockServletContext;
+import org.springframework.web.context.WebApplicationContext;
+
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Tests for {@link SpringBootServletInitializerTests}.
+ *
+ * @author Phillip Webb
+ */
+public class SpringBootServletInitializerTests {
+
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
+	private ServletContext servletContext = new MockServletContext();
+
+	private SpringApplication application;
+
+	@Test
+	public void failsWithoutConfigure() throws Exception {
+		this.thrown.expect(IllegalStateException.class);
+		this.thrown.expectMessage("No SpringApplication sources have been defined");
+		new MockSpringBootServletInitializer()
+				.createRootApplicationContext(this.servletContext);
+	}
+
+	@Test
+	public void withConfigurationAnnotation() throws Exception {
+		new WithConfigurationAnnotation()
+				.createRootApplicationContext(this.servletContext);
+		assertThat(this.application.getSources(),
+				equalToSet(WithConfigurationAnnotation.class, ErrorPageFilter.class));
+	}
+
+	@Test
+	public void withConfiguredSource() throws Exception {
+		new WithConfiguredSource().createRootApplicationContext(this.servletContext);
+		assertThat(this.application.getSources(),
+				equalToSet(Config.class, ErrorPageFilter.class));
+	}
+
+	private Matcher<? super Set<Object>> equalToSet(Object... items) {
+		Set<Object> set = new LinkedHashSet<Object>();
+		for (Object item : items) {
+			set.add(item);
+		}
+		return equalTo(set);
+	}
+
+	private class MockSpringBootServletInitializer extends SpringBootServletInitializer {
+
+		@Override
+		protected WebApplicationContext run(SpringApplication application) {
+			SpringBootServletInitializerTests.this.application = application;
+			return null;
+		};
+
+	}
+
+	@Configuration
+	public class WithConfigurationAnnotation extends MockSpringBootServletInitializer {
+	}
+
+	public class WithConfiguredSource extends MockSpringBootServletInitializer {
+
+		@Override
+		protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
+			return application.sources(Config.class);
+		}
+
+	}
+
+	@Configuration
+	public static class Config {
+
+	}
+
+}