Warn on @ComponentScan of default package

Add ConfigurationWarningsApplicationContextInitializer to report
warnings for common configuration mistakes. Currently the initializer
will log a warning if @ComponentScan is used on a @Configuration class
in the "default" package.

Fixes gh-2050

spring-boot/src/main/java/org/springframework/boot/context/ConfigurationWarningsApplicationContextInitializer.java

+/*
+ * 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;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.annotation.AnnotatedBeanDefinition;
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
+import org.springframework.context.ApplicationContextInitializer;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.core.Ordered;
+import org.springframework.core.PriorityOrdered;
+import org.springframework.core.annotation.AnnotationAttributes;
+import org.springframework.core.type.AnnotationMetadata;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.ObjectUtils;
+import org.springframework.util.StringUtils;
+
+/**
+ * {@link ApplicationContextInitializer} to report warnings for common misconfiguration
+ * mistakes.
+ *
+ * @author Phillip Webb
+ * @since 1.2.0
+ */
+public class ConfigurationWarningsApplicationContextInitializer implements
+		ApplicationContextInitializer<ConfigurableApplicationContext> {
+
+	private static Log logger = LogFactory
+			.getLog(ConfigurationWarningsApplicationContextInitializer.class);
+
+	@Override
+	public void initialize(ConfigurableApplicationContext context) {
+		context.addBeanFactoryPostProcessor(new ConfigurationWarningsPostProcessor(
+				getChecks()));
+	}
+
+	/**
+	 * Returns the checks that should be applied.
+	 * @return the checks to apply
+	 */
+	protected Check[] getChecks() {
+		return new Check[] { new ComponentScanDefaultPackageCheck() };
+	}
+
+	/**
+	 * {@link BeanDefinitionRegistryPostProcessor} to report warnings.
+	 */
+	protected final static class ConfigurationWarningsPostProcessor implements
+			PriorityOrdered, BeanDefinitionRegistryPostProcessor {
+
+		private Check[] checks;
+
+		public ConfigurationWarningsPostProcessor(Check[] checks) {
+			this.checks = checks;
+		}
+
+		@Override
+		public int getOrder() {
+			return Ordered.LOWEST_PRECEDENCE - 1;
+		}
+
+		@Override
+		public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
+				throws BeansException {
+		}
+
+		@Override
+		public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)
+				throws BeansException {
+			for (Check check : this.checks) {
+				String message = check.getWarning(registry);
+				if (StringUtils.hasLength(message)) {
+					warn(message);
+				}
+			}
+
+		}
+
+		private void warn(String message) {
+			if (logger.isWarnEnabled()) {
+				logger.warn("\n\n** WARNING ** : " + message + "\n\n");
+			}
+		}
+
+	}
+
+	/**
+	 * A single check that can be applied.
+	 */
+	protected static interface Check {
+
+		/**
+		 * Returns a warning if the check fails or {@code null} if there are no problems.
+		 * @param registry the {@link BeanDefinitionRegistry}
+		 * @return a warning message or {@code null}
+		 */
+		String getWarning(BeanDefinitionRegistry registry);
+
+	}
+
+	/**
+	 * {@link Check} for {@code @ComponentScan} on the default package.
+	 */
+	protected static class ComponentScanDefaultPackageCheck implements Check {
+
+		@Override
+		public String getWarning(BeanDefinitionRegistry registry) {
+			if (isComponentScanningDefaultPackage(registry)) {
+				return "Your ApplicationContext is unlikely to start due to a "
+						+ "@ComponentScan of the default package.";
+			}
+			return null;
+		}
+
+		private boolean isComponentScanningDefaultPackage(BeanDefinitionRegistry registry) {
+			String[] names = registry.getBeanDefinitionNames();
+			for (String name : names) {
+				BeanDefinition definition = registry.getBeanDefinition(name);
+				if (definition instanceof AnnotatedBeanDefinition) {
+					AnnotatedBeanDefinition annotatedDefinition = (AnnotatedBeanDefinition) definition;
+					if (isScanningDefaultPackage(annotatedDefinition.getMetadata())) {
+						return true;
+					}
+				}
+			}
+			return false;
+		}
+
+		private boolean isScanningDefaultPackage(AnnotationMetadata metadata) {
+			AnnotationAttributes attributes = AnnotationAttributes.fromMap(metadata
+					.getAnnotationAttributes(ComponentScan.class.getName(), true));
+			if (attributes != null && hasNoScanPackageSpecified(attributes)) {
+				if (isInDefaultPackage(metadata.getClassName())) {
+					return true;
+				}
+			}
+			return false;
+		}
+
+		private boolean hasNoScanPackageSpecified(AnnotationAttributes attributes) {
+			return isAllEmpty(attributes, "value", "basePackages", "basePackageClasses");
+		}
+
+		private boolean isAllEmpty(AnnotationAttributes attributes, String... names) {
+			for (String name : names) {
+				if (!ObjectUtils.isEmpty(attributes.getStringArray(name))) {
+					return false;
+				}
+			}
+			return true;
+		}
+
+		protected boolean isInDefaultPackage(String className) {
+			String packageName = ClassUtils.getPackageName(className);
+			return StringUtils.isEmpty(packageName);
+		}
+	}
+
+}

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

@@ -9,6 +9,7 @@ org.springframework.boot.context.event.EventPublishingRunListener
 
 # Application Context Initializers
 org.springframework.context.ApplicationContextInitializer=\
+org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,\
 org.springframework.boot.context.ContextIdApplicationContextInitializer,\
 org.springframework.boot.context.config.DelegatingApplicationContextInitializer
 

spring-boot/src/test/java/org/springframework/boot/builder/SpringApplicationBuilderTests.java

@@ -239,7 +239,7 @@ public class SpringApplicationBuilderTests {
 		SpringApplicationBuilder application = new SpringApplicationBuilder(
 				ExampleConfig.class).web(false);
 		this.context = application.run();
-		assertEquals(2, application.application().getInitializers().size());
+		assertEquals(3, application.application().getInitializers().size());
 	}
 
 	@Test
@@ -247,7 +247,7 @@ public class SpringApplicationBuilderTests {
 		SpringApplicationBuilder application = new SpringApplicationBuilder(
 				ExampleConfig.class).child(ChildConfig.class).web(false);
 		this.context = application.run();
-		assertEquals(3, application.application().getInitializers().size());
+		assertEquals(4, application.application().getInitializers().size());
 	}
 
 	@Test
@@ -261,7 +261,7 @@ public class SpringApplicationBuilderTests {
 					}
 				});
 		this.context = application.run();
-		assertEquals(3, application.application().getInitializers().size());
+		assertEquals(4, application.application().getInitializers().size());
 	}
 
 	@Configuration

spring-boot/src/test/java/org/springframework/boot/context/ConfigurationWarningsApplicationContextInitializerTests.java

+/*
+ * 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;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer.ComponentScanDefaultPackageCheck;
+import org.springframework.boot.context.configwarnings.InDefaultPackageConfiguration;
+import org.springframework.boot.context.configwarnings.InDefaultPackageWithBasePackageClassesConfiguration;
+import org.springframework.boot.context.configwarnings.InDefaultPackageWithBasePackagesConfiguration;
+import org.springframework.boot.context.configwarnings.InDefaultPackageWithMetaAnnotationConfiguration;
+import org.springframework.boot.context.configwarnings.InDefaultPackageWithValueConfiguration;
+import org.springframework.boot.context.configwarnings.InDefaultPackageWithoutScanConfiguration;
+import org.springframework.boot.context.configwarnings.InRealPackageConfiguration;
+import org.springframework.boot.test.OutputCapture;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.not;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Tests for {@link ConfigurationWarningsApplicationContextInitializer}.
+ *
+ * @author Phillip Webb
+ */
+public class ConfigurationWarningsApplicationContextInitializerTests {
+
+	private static final String SCAN_WARNING = "Your ApplicationContext is unlikely to "
+			+ "start due to a @ComponentScan of the default package";
+
+	@Rule
+	public OutputCapture output = new OutputCapture();
+
+	@Test
+	public void logWarningInDefaultPackage() {
+		load(InDefaultPackageConfiguration.class);
+		assertThat(this.output.toString(), containsString(SCAN_WARNING));
+	}
+
+	@Test
+	public void logWarningInDefaultPackageAndMetaAnnotation() {
+		load(InDefaultPackageWithMetaAnnotationConfiguration.class);
+		assertThat(this.output.toString(), containsString(SCAN_WARNING));
+	}
+
+	@Test
+	public void noLogIfInRealPackage() throws Exception {
+		load(InRealPackageConfiguration.class);
+		assertThat(this.output.toString(), not(containsString(SCAN_WARNING)));
+	}
+
+	@Test
+	public void noLogWithoutComponetScanAnnotation() throws Exception {
+		load(InDefaultPackageWithoutScanConfiguration.class);
+		assertThat(this.output.toString(), not(containsString(SCAN_WARNING)));
+	}
+
+	@Test
+	public void noLogIfHasValue() throws Exception {
+		load(InDefaultPackageWithValueConfiguration.class);
+		assertThat(this.output.toString(), not(containsString(SCAN_WARNING)));
+	}
+
+	@Test
+	public void noLogIfHasBasePackages() throws Exception {
+		load(InDefaultPackageWithBasePackagesConfiguration.class);
+		assertThat(this.output.toString(), not(containsString(SCAN_WARNING)));
+	}
+
+	@Test
+	public void noLogIfHasBasePackageClasses() throws Exception {
+		load(InDefaultPackageWithBasePackageClassesConfiguration.class);
+		assertThat(this.output.toString(), not(containsString(SCAN_WARNING)));
+	}
+
+	private void load(Class<?> configClass) {
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+		new TestConfigurationWarningsApplicationContextInitializer().initialize(context);
+		context.register(configClass);
+		try {
+			context.refresh();
+		}
+		catch (Exception ex) {
+			ex.printStackTrace();
+		}
+		finally {
+			context.close();
+		}
+	}
+
+	/**
+	 * Testable version of {@link ConfigurationWarningsApplicationContextInitializer}.
+	 */
+	public static class TestConfigurationWarningsApplicationContextInitializer extends
+			ConfigurationWarningsApplicationContextInitializer {
+
+		@Override
+		protected Check[] getChecks() {
+			return new Check[] { new TestComponentScanDefaultPackageCheck() };
+		}
+
+	}
+
+	/**
+	 * Testable ComponentScanDefaultPackageCheck that doesn't need to use the default
+	 * package.
+	 */
+	static class TestComponentScanDefaultPackageCheck extends
+			ComponentScanDefaultPackageCheck {
+
+		@Override
+		protected boolean isInDefaultPackage(String className) {
+			return className.contains("InDefault");
+		}
+
+	}
+
+}

spring-boot/src/test/java/org/springframework/boot/context/configwarnings/InDefaultPackageConfiguration.java

+/*
+ * 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.configwarnings;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan
+public class InDefaultPackageConfiguration {
+}

spring-boot/src/test/java/org/springframework/boot/context/configwarnings/InDefaultPackageWithBasePackageClassesConfiguration.java

+/*
+ * 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.configwarnings;
+
+import org.springframework.boot.context.configwarnings.nested.ExampleBean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan(basePackageClasses = ExampleBean.class)
+public class InDefaultPackageWithBasePackageClassesConfiguration {
+}

spring-boot/src/test/java/org/springframework/boot/context/configwarnings/InDefaultPackageWithBasePackagesConfiguration.java

+/*
+ * 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.configwarnings;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan(basePackages = "org.springframework.boot.context.configwarnings.nested")
+public class InDefaultPackageWithBasePackagesConfiguration {
+}

spring-boot/src/test/java/org/springframework/boot/context/configwarnings/InDefaultPackageWithMetaAnnotationConfiguration.java

+/*
+ * 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.configwarnings;
+
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@MetaComponentScan
+public class InDefaultPackageWithMetaAnnotationConfiguration {
+}

spring-boot/src/test/java/org/springframework/boot/context/configwarnings/InDefaultPackageWithValueConfiguration.java

+/*
+ * 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.configwarnings;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("org.springframework.boot.context.configwarnings.nested")
+public class InDefaultPackageWithValueConfiguration {
+}

spring-boot/src/test/java/org/springframework/boot/context/configwarnings/InDefaultPackageWithoutScanConfiguration.java

+/*
+ * 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.configwarnings;
+
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+public class InDefaultPackageWithoutScanConfiguration {
+}

spring-boot/src/test/java/org/springframework/boot/context/configwarnings/InRealPackageConfiguration.java

+/*
+ * 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.configwarnings;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan
+public class InRealPackageConfiguration {
+}
\ No newline at end of file

spring-boot/src/test/java/org/springframework/boot/context/configwarnings/MetaComponentScan.java

+/*
+ * 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.configwarnings;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.context.annotation.ComponentScan;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.TYPE)
+@ComponentScan
+public @interface MetaComponentScan {
+
+}

spring-boot/src/test/java/org/springframework/boot/context/configwarnings/nested/ExampleBean.java

+/*
+ * 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.configwarnings.nested;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class ExampleBean {
+
+}