While a {@link #name()} attribute is available, the default strategy for determining * the name of a bean is to use the name of the Bean method. This is convenient and - * intuitive, but if explicit naming is desired, the {@link #name()} attribute may be used. - * Also note that {@link #name()} accepts an array of Strings. This is in order to allow + * intuitive, but if explicit naming is desired, the {@code name()} attribute may be used. + * Also note that {@code name()} accepts an array of Strings. This is in order to allow * for specifying multiple names (i.e., aliases) for a single bean. * *
The @Bean annotation may be used on any methods in an @Component
@@ -56,6 +56,27 @@ import org.springframework.beans.factory.annotation.Autowire;
* subclassing of each such configuration class at runtime. As a consequence, configuration
* classes and their factory methods must not be marked as final or private in this mode.
*
+ *
Special consideration must be taken for {@code @Bean} methods that return Spring + * {@link org.springframework.beans.factory.config.BeanFactoryPostProcessor BeanFactoryPostProcessor} + * ({@code BFPP}) types. Because {@code BFPP} objects must be instantiated very early in the + * container lifecycle, they can interfere with processing of annotations such as {@code @Autowired}, + * {@code @Value}, and {@code @PostConstruct} within {@code @Configuration} classes. To avoid these + * lifecycle issues, mark {@code BFPP}-returning {@code @Bean} methods as {@code static}. For example: + *
+ * @Bean
+ * public static PropertyPlaceholderConfigurer ppc() {
+ * // instantiate, configure and return ppc ...
+ * }
+ *
+ * By marking this method as {@code static}, it can be invoked without causing instantiation of its
+ * declaring {@code @Configuration} class, thus avoiding the above-mentioned lifecycle conflicts.
+ * Note however that {@code static} {@code @Bean} methods will not be enhanced for scoping and AOP
+ * semantics as mentioned above. This works out in {@code BFPP} cases, as they are not typically
+ * referenced by other {@code @Bean} methods. As a reminder, a WARN-level log message will be
+ * issued for any non-static {@code @Bean} methods having a return type assignable to
+ * {@code BeanFactoryPostProcessor}.
+ *
* @author Rod Johnson
* @author Costin Leau
* @author Chris Beams
diff --git a/org.springframework.context/src/main/java/org/springframework/context/annotation/BeanMethod.java b/org.springframework.context/src/main/java/org/springframework/context/annotation/BeanMethod.java
index 4b5d762d1d5..939cb6b300e 100644
--- a/org.springframework.context/src/main/java/org/springframework/context/annotation/BeanMethod.java
+++ b/org.springframework.context/src/main/java/org/springframework/context/annotation/BeanMethod.java
@@ -39,39 +39,25 @@ final class BeanMethod extends ConfigurationMethod {
@Override
public void validate(ProblemReporter problemReporter) {
+ if (getMetadata().isStatic()) {
+ // static @Bean methods have no constraints to validate -> return immediately
+ return;
+ }
+
if (this.configurationClass.getMetadata().isAnnotated(Configuration.class.getName())) {
if (!getMetadata().isOverridable()) {
+ // instance @Bean methods within @Configuration classes must be overridable to accommodate CGLIB
problemReporter.error(new NonOverridableMethodError());
}
}
- else {
- if (getMetadata().isStatic()) {
- problemReporter.error(new StaticMethodError());
- }
- }
}
- /**
- * {@link Bean} methods must be overridable in order to accommodate CGLIB.
- */
+
private class NonOverridableMethodError extends Problem {
public NonOverridableMethodError() {
- super(String.format("Method '%s' must not be private, final or static; change the method's modifiers to continue",
- getMetadata().getMethodName()), getResourceLocation());
- }
- }
-
-
- /**
- * {@link Bean} methods must at least not be static in the non-CGLIB case.
- */
- private class StaticMethodError extends Problem {
-
- public StaticMethodError() {
- super(String.format("Method '%s' must not be static; remove the method's static modifier to continue",
+ super(String.format("@Bean method '%s' must not be private or final; change the method's modifiers to continue",
getMetadata().getMethodName()), getResourceLocation());
}
}
-
}
diff --git a/org.springframework.context/src/main/java/org/springframework/context/annotation/ConfigurationClassBeanDefinitionReader.java b/org.springframework.context/src/main/java/org/springframework/context/annotation/ConfigurationClassBeanDefinitionReader.java
index fd4b13e7d97..d9e687b59e6 100644
--- a/org.springframework.context/src/main/java/org/springframework/context/annotation/ConfigurationClassBeanDefinitionReader.java
+++ b/org.springframework.context/src/main/java/org/springframework/context/annotation/ConfigurationClassBeanDefinitionReader.java
@@ -162,8 +162,16 @@ public class ConfigurationClassBeanDefinitionReader {
RootBeanDefinition beanDef = new ConfigurationClassBeanDefinition(configClass);
beanDef.setResource(configClass.getResource());
beanDef.setSource(this.sourceExtractor.extractSource(metadata, configClass.getResource()));
- beanDef.setFactoryBeanName(configClass.getBeanName());
- beanDef.setUniqueFactoryMethodName(metadata.getMethodName());
+ if (metadata.isStatic()) {
+ // static @Bean method
+ beanDef.setBeanClassName(configClass.getMetadata().getClassName());
+ beanDef.setFactoryMethodName(metadata.getMethodName());
+ }
+ else {
+ // instance @Bean method
+ beanDef.setFactoryBeanName(configClass.getBeanName());
+ beanDef.setUniqueFactoryMethodName(metadata.getMethodName());
+ }
beanDef.setAutowireMode(RootBeanDefinition.AUTOWIRE_CONSTRUCTOR);
beanDef.setAttribute(RequiredAnnotationBeanPostProcessor.SKIP_REQUIRED_CHECK_ATTRIBUTE, Boolean.TRUE);
diff --git a/org.springframework.context/src/main/java/org/springframework/context/annotation/ConfigurationClassEnhancer.java b/org.springframework.context/src/main/java/org/springframework/context/annotation/ConfigurationClassEnhancer.java
index 2e4bc37de9b..23a6baff8ee 100644
--- a/org.springframework.context/src/main/java/org/springframework/context/annotation/ConfigurationClassEnhancer.java
+++ b/org.springframework.context/src/main/java/org/springframework/context/annotation/ConfigurationClassEnhancer.java
@@ -33,6 +33,7 @@ import org.springframework.aop.scope.ScopedProxyFactoryBean;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.FactoryBean;
+import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.util.Assert;
@@ -239,6 +240,15 @@ class ConfigurationClassEnhancer {
return this.beanFactory.getBean(beanName);
}
+ if (BeanFactoryPostProcessor.class.isAssignableFrom(beanMethod.getReturnType())) {
+ logger.warn(String.format("@Bean method %s.%s is non-static and returns an object " +
+ "assignable to Spring's BeanFactoryPostProcessor interface. This will " +
+ "result in a failure to process annotations such as @Autowired, " +
+ "@Resource and @PostConstruct within the method's declaring " +
+ "@Configuration class. Add the 'static' modifier to this method to avoid" +
+ "these container lifecycle issues; see @Bean Javadoc for complete details",
+ beanMethod.getDeclaringClass().getSimpleName(), beanMethod.getName()));
+ }
return cglibMethodProxy.invokeSuper(enhancedConfigInstance, beanMethodArgs);
}
diff --git a/org.springframework.context/src/test/java/org/springframework/context/annotation/ConfigurationClassAndBFPPTests.java b/org.springframework.context/src/test/java/org/springframework/context/annotation/ConfigurationClassAndBFPPTests.java
new file mode 100644
index 00000000000..060c9f6bf2c
--- /dev/null
+++ b/org.springframework.context/src/test/java/org/springframework/context/annotation/ConfigurationClassAndBFPPTests.java
@@ -0,0 +1,122 @@
+/*
+ * 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.not;
+import static org.hamcrest.CoreMatchers.notNullValue;
+import static org.hamcrest.CoreMatchers.nullValue;
+import static org.hamcrest.CoreMatchers.sameInstance;
+import static org.junit.Assert.assertThat;
+
+import org.junit.Test;
+import org.springframework.beans.BeansException;
+import org.springframework.beans.TestBean;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+
+/**
+ * Tests semantics of declaring {@link BeanFactoryPostProcessor}-returning @Bean
+ * methods, specifically as regards static @Bean methods and the avoidance of
+ * container lifecycle issues when BFPPs are in the mix.
+ *
+ * @author Chris Beams
+ * @since 3.1
+ */
+public class ConfigurationClassAndBFPPTests {
+
+ @Test
+ public void autowiringFailsWithBFPPAsInstanceMethod() {
+ AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
+ ctx.register(TestBeanConfig.class, AutowiredConfigWithBFPPAsInstanceMethod.class);
+ ctx.refresh();
+ // instance method BFPP interferes with lifecycle -> autowiring fails!
+ // WARN-level logging should have been issued about returning BFPP from non-static @Bean method
+ assertThat(ctx.getBean(AutowiredConfigWithBFPPAsInstanceMethod.class).autowiredTestBean, nullValue());
+ }
+
+ @Test
+ public void autowiringSucceedsWithBFPPAsStaticMethod() {
+ AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
+ ctx.register(TestBeanConfig.class, AutowiredConfigWithBFPPAsStaticMethod.class);
+ ctx.refresh();
+ // static method BFPP does not interfere with lifecycle -> autowiring succeeds
+ assertThat(ctx.getBean(AutowiredConfigWithBFPPAsStaticMethod.class).autowiredTestBean, notNullValue());
+ }
+
+
+ @Configuration
+ static class TestBeanConfig {
+ @Bean
+ public TestBean testBean() {
+ return new TestBean();
+ }
+ }
+
+
+ @Configuration
+ static class AutowiredConfigWithBFPPAsInstanceMethod {
+ @Autowired TestBean autowiredTestBean;
+
+ @Bean
+ public BeanFactoryPostProcessor bfpp() {
+ return new BeanFactoryPostProcessor() {
+ public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
+ // no-op
+ }
+ };
+ }
+ }
+
+
+ @Configuration
+ static class AutowiredConfigWithBFPPAsStaticMethod {
+ @Autowired TestBean autowiredTestBean;
+
+ @Bean
+ public static final BeanFactoryPostProcessor bfpp() {
+ return new BeanFactoryPostProcessor() {
+ public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
+ // no-op
+ }
+ };
+ }
+ }
+
+
+ @Test
+ @SuppressWarnings("static-access")
+ public void staticBeanMethodsDoNotRespectScoping() {
+ AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
+ ctx.register(ConfigWithStaticBeanMethod.class);
+ ctx.refresh();
+
+ ConfigWithStaticBeanMethod config = ctx.getBean(ConfigWithStaticBeanMethod.class);
+ assertThat(config.testBean(), not(sameInstance(config.testBean())));
+ }
+
+
+ @Configuration
+ static class ConfigWithStaticBeanMethod {
+ @Bean
+ public static TestBean testBean() {
+ return new TestBean("foo");
+ }
+ }
+
+
+}