Allow recursive use of @ComponentScan

Prior to this change, @ComponentScan annotations were only processed at
the first level of depth.  Now, the set of bean definitions resulting
from each declaration of @ComponentScan is checked for configuration
classes that declare @ComponentScan, and recursion is performed as
necessary.

Cycles between @ComponentScan declarations are detected as well. See
CircularComponentScanException.

Issue: SPR-8307

org.springframework.context/src/test/java/org/springframework/context/annotation/AsmCircularImportDetectionTests.java

@@ -16,7 +16,9 @@
 package org.springframework.context.annotation;
 
 import org.springframework.beans.factory.parsing.FailFastProblemReporter;
+import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.core.env.DefaultEnvironment;
+import org.springframework.core.io.DefaultResourceLoader;
 import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
 
 /**
@@ -33,7 +35,12 @@ public class AsmCircularImportDetectionTests extends AbstractCircularImportDetec
 
 	@Override
 	protected ConfigurationClassParser newParser() {
-		return new ConfigurationClassParser(new CachingMetadataReaderFactory(), new FailFastProblemReporter(), new DefaultEnvironment());
+		return new ConfigurationClassParser(
+				new CachingMetadataReaderFactory(),
+				new FailFastProblemReporter(),
+				new DefaultEnvironment(),
+				new DefaultResourceLoader(),
+				new DefaultListableBeanFactory());
 	}
 
 	@Override

org.springframework.context/src/test/java/org/springframework/context/annotation/ComponentScanAnnotationRecursionTests.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2002-2011 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.context.annotation;
+
+import static org.hamcrest.CoreMatchers.sameInstance;
+import static org.junit.Assert.assertThat;
+
+import org.junit.Test;
+import org.springframework.context.annotation.componentscan.cycle.left.LeftConfig;
+import org.springframework.context.annotation.componentscan.level1.Level1Config;
+import org.springframework.context.annotation.componentscan.level2.Level2Config;
+import org.springframework.context.annotation.componentscan.level3.Level3Component;
+
+/**
+ * Tests ensuring that configuration clasess marked with @ComponentScan
+ * may be processed recursively
+ *
+ * @author Chris Beams
+ * @since 3.1
+ */
+public class ComponentScanAnnotationRecursionTests {
+
+	@Test
+	public void recursion() {
+		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
+		ctx.register(Level1Config.class);
+		ctx.refresh();
+
+		// assert that all levels have been detected
+		ctx.getBean(Level1Config.class);
+		ctx.getBean(Level2Config.class);
+		ctx.getBean(Level3Component.class);
+
+		// assert that enhancement is working
+		assertThat(ctx.getBean("level1Bean"), sameInstance(ctx.getBean("level1Bean")));
+		assertThat(ctx.getBean("level2Bean"), sameInstance(ctx.getBean("level2Bean")));
+	}
+
+	@Test(expected=CircularComponentScanException.class)
+	public void cycleDetection() {
+		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
+		ctx.register(LeftConfig.class);
+		ctx.refresh();
+	}
+
+}

org.springframework.context/src/test/java/org/springframework/context/annotation/componentscan/cycle/left/LeftConfig.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2002-2011 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.context.annotation.componentscan.cycle.left;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("org.springframework.context.annotation.componentscan.cycle.right")
+public class LeftConfig {
+
+}

org.springframework.context/src/test/java/org/springframework/context/annotation/componentscan/cycle/right/RightConfig.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2002-2011 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.context.annotation.componentscan.cycle.right;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("org.springframework.context.annotation.componentscan.cycle.left")
+public class RightConfig {
+
+}

org.springframework.context/src/test/java/org/springframework/context/annotation/componentscan/level1/Level1Config.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2002-2011 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.context.annotation.componentscan.level1;
+
+import org.springframework.beans.TestBean;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("org.springframework.context.annotation.componentscan.level2")
+public class Level1Config {
+	@Bean
+	public TestBean level1Bean() {
+		return new TestBean("level1Bean");
+	}
+}

org.springframework.context/src/test/java/org/springframework/context/annotation/componentscan/level2/Level2Config.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2002-2011 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.context.annotation.componentscan.level2;
+
+import org.springframework.beans.TestBean;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("org.springframework.context.annotation.componentscan.level3")
+public class Level2Config {
+	@Bean
+	public TestBean level2Bean() {
+		return new TestBean("level2Bean");
+	}
+}

org.springframework.context/src/test/java/org/springframework/context/annotation/componentscan/level3/Level3Component.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2002-2011 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.context.annotation.componentscan.level3;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Level3Component {
+
+}