Recommendation for consistent @Profile declarations on overloaded @bean methods

Issue: SPR-15266
(cherry picked from commit 5d3249f)

Author: jhoeller

spring-context/src/main/java/org/springframework/context/annotation/Conditional.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -16,6 +16,7 @@
 
 package org.springframework.context.annotation;
 
+import java.lang.annotation.Documented;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -55,8 +56,9 @@
  * @since 4.0
  * @see Condition
  */
-@Retention(RetentionPolicy.RUNTIME)
 @Target({ElementType.TYPE, ElementType.METHOD})
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
 public @interface Conditional {
 
 	/**

spring-context/src/main/java/org/springframework/context/annotation/Configuration.java

@@ -231,7 +231,7 @@
  * indicate they should be processed only if a given profile or profiles are <em>active</em>:
  *
  * <pre class="code">
- * &#064;Profile("embedded")
+ * &#064;Profile("development")
  * &#064;Configuration
  * public class EmbeddedDatabaseConfig {
  *
@@ -251,6 +251,22 @@
  *     }
  * }</pre>
  *
+ * Alternatively, you may also declare profile conditions at the {@code @Bean} method level,
+ * e.g. for alternative bean variants within the same configuration class:
+ *
+ * <pre class="code">
+ * &#064;Configuration
+ * public class ProfileDatabaseConfig {
+ *
+ *     &#064;Bean("dataSource")
+ *     &#064;Profile("development")
+ *     public DataSource embeddedDatabase() { ... }
+ *
+ *     &#064;Bean("dataSource")
+ *     &#064;Profile("production")
+ *     public DataSource productionDatabase() { ... }
+ * }</pre>
+ *
  * See the {@link Profile @Profile} and {@link org.springframework.core.env.Environment}
  * javadocs for further details.
  *

spring-context/src/main/java/org/springframework/context/annotation/Profile.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -57,12 +57,24 @@
  *
  * <p>If a given profile is prefixed with the NOT operator ({@code !}), the annotated
  * component will be registered if the profile is <em>not</em> active &mdash; for example,
- * given {@code @Profile({"p1", "!p2"})}, registration will occur if profile 'p1' is active or
- * if profile 'p2' is <em>not</em> active.
+ * given {@code @Profile({"p1", "!p2"})}, registration will occur if profile 'p1' is active
+ * or if profile 'p2' is <em>not</em> active.
  *
  * <p>If the {@code @Profile} annotation is omitted, registration will occur regardless
  * of which (if any) profiles are active.
  *
+ * <p><b>NOTE:</b> With {@code @Profile} on {@code @Bean} methods, a special scenario may
+ * apply: In the case of overloaded {@code @Bean} methods of the same Java method name
+ * (analogous to constructor overloading), an {@code @Profile} condition needs to be
+ * consistently declared on all overloaded methods. If the conditions are inconsistent,
+ * only the condition on the first declaration among the overloaded methods will matter.
+ * {@code @Profile} can therefore not be used to select an overloaded method with a
+ * particular argument signature over another; resolution between all factory methods
+ * for the same bean follows Spring's constructor resolution algorithm at creation time.
+ * <b>Use distinct Java method names pointing to the same {@link @Bean#name bean name}
+ * if you'd like to define alternative beans with different profile conditions</b>;
+ * see {@code ProfileDatabaseConfig} in {@link Configuration @Configuration}'s javadoc.
+ *
  * <p>When defining Spring beans via XML, the {@code "profile"} attribute of the
  * {@code <beans>} element may be used. See the documentation in the
  * {@code spring-beans} XSD (version 3.1 or greater) for details.
@@ -78,8 +90,8 @@
  * @see Conditional
  * @see org.springframework.test.context.ActiveProfiles
  */
-@Retention(RetentionPolicy.RUNTIME)
 @Target({ElementType.TYPE, ElementType.METHOD})
+@Retention(RetentionPolicy.RUNTIME)
 @Documented
 @Conditional(ProfileCondition.class)
 public @interface Profile {

src/asciidoc/core-beans.adoc

@@ -7402,6 +7402,9 @@ jdbc.password=
 	}
 ----
 
+
+
+
 [[beans-environment]]
 == Environment abstraction
 
@@ -7423,6 +7426,8 @@ on. The role of the `Environment` object with relation to properties is to provi
 user with a convenient service interface for configuring property sources and resolving
 properties from them.
 
+
+
 [[beans-definition-profiles]]
 === Bean definition profiles
 
@@ -7497,7 +7502,7 @@ can rewrite the `dataSource` configuration as follows:
 [subs="verbatim,quotes"]
 ----
 	@Configuration
-	**@Profile("dev")**
+	**@Profile("development")**
 	public class StandaloneDataConfig {
 
 		@Bean
@@ -7549,56 +7554,76 @@ of creating a custom _composed annotation_. The following example defines a cust
 	}
 ----
 
+[TIP]
+====
+If a `@Configuration` class is marked with `@Profile`, all of the `@Bean` methods and
+`@Import` annotations associated with that class will be bypassed unless one or more of
+the specified profiles are active. If a `@Component` or `@Configuration` class is marked
+with `@Profile({"p1", "p2"})`, that class will not be registered/processed unless
+profiles 'p1' and/or 'p2' have been activated. If a given profile is prefixed with the
+NOT operator (`!`), the annotated element will be registered if the profile is **not**
+active. For example, given `@Profile({"p1", "!p2"})`, registration will occur if profile
+'p1' is active or if profile 'p2' is not active.
+====
+
 `@Profile` can also be declared at the method level to include only one particular bean
-of a configuration class:
+of a configuration class, e.g. for alternative variants of a particular bean:
 
 [source,java,indent=0]
 [subs="verbatim,quotes"]
 ----
 	@Configuration
 	public class AppConfig {
 
-		@Bean
-		**@Profile("dev")**
-		public DataSource devDataSource() {
+		@Bean("dataSource")
+		**@Profile("development")**
+		public DataSource standaloneDataSource() {
 			return new EmbeddedDatabaseBuilder()
 				.setType(EmbeddedDatabaseType.HSQL)
 				.addScript("classpath:com/bank/config/sql/schema.sql")
 				.addScript("classpath:com/bank/config/sql/test-data.sql")
 				.build();
 		}
 
-		@Bean
+		@Bean("dataSource")
 		**@Profile("production")**
-		public DataSource productionDataSource() throws Exception {
+		public DataSource jndiDataSource() throws Exception {
 			Context ctx = new InitialContext();
 			return (DataSource) ctx.lookup("java:comp/env/jdbc/datasource");
 		}
 	}
 ----
 
-[TIP]
+[NOTE]
 ====
-If a `@Configuration` class is marked with `@Profile`, all of the `@Bean` methods and
-`@Import` annotations associated with that class will be bypassed unless one or more of
-the specified profiles are active. If a `@Component` or `@Configuration` class is marked
-with `@Profile({"p1", "p2"})`, that class will not be registered/processed unless
-profiles 'p1' and/or 'p2' have been activated. If a given profile is prefixed with the
-NOT operator (`!`), the annotated element will be registered if the profile is **not**
-active. For example, given `@Profile({"p1", "!p2"})`, registration will occur if profile
-'p1' is active or if profile 'p2' is not active.
+With `@Profile` on `@Bean` methods, a special scenario may apply: In the case of
+overloaded `@Bean` methods of the same Java method name (analogous to constructor
+overloading), an `@Profile` condition needs to be consistently declared on all
+overloaded methods. If the conditions are inconsistent, only the condition on the
+first declaration among the overloaded methods will matter. `@Profile` can therefore
+not be used to select an overloaded method with a particular argument signature over
+another; resolution between all factory methods for the same bean follows Spring's
+constructor resolution algorithm at creation time.
+
+If you would like to define alternative beans with different profile conditions,
+use distinct Java method names pointing to the same bean name via the `@Bean` name
+attribute, as indicated in the example above. If the argument signatures are all
+the same (e.g. all of the variants have no-arg factory methods), this is the only
+way to represent such an arrangement in a valid Java class in the first place
+(since there can only be one method of a particular name and argument signature).
 ====
 
+
 [[beans-definition-profiles-xml]]
-=== XML bean definition profiles
+==== XML bean definition profiles
 
 The XML counterpart is the `profile` attribute of the `<beans>` element. Our sample
 configuration above can be rewritten in two XML files as follows:
 
 [source,xml,indent=0]
 [subs="verbatim,quotes"]
 ----
-	<beans profile="dev"
+	<beans profile="development"
 		xmlns="http://www.springframework.org/schema/beans"
 		xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 		xmlns:jdbc="http://www.springframework.org/schema/jdbc"
@@ -7637,7 +7662,7 @@ It is also possible to avoid that split and nest `<beans/>` elements within the
 
 		<!-- other bean definitions -->
 
-		<beans profile="dev">
+		<beans profile="development">
 			<jdbc:embedded-database id="dataSource">
 				<jdbc:script location="classpath:com/bank/config/sql/schema.sql"/>
 				<jdbc:script location="classpath:com/bank/config/sql/test-data.sql"/>
@@ -7671,7 +7696,7 @@ it programmatically against the `Environment` API which is available via an
 [subs="verbatim,quotes"]
 ----
 	AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
-	ctx.getEnvironment().setActiveProfiles("dev");
+	ctx.getEnvironment().setActiveProfiles("development");
 	ctx.register(SomeConfig.class, StandaloneDataConfig.class, JndiDataConfig.class);
 	ctx.refresh();
 ----