spring-context中@Profile注解的源码解析说明

spring版本为5.0.11

@Profile:指定组件在哪个环境的情况下才能被注册到容器中，不指定，任何环境下都能注册这个组件

  1) 加了环境标识的bean，只有这个环境被激活的时候才能注册到容器中。默认是default环境
  2) 写在配置类上，只有是指定的环境的时候，整个配置类里面的所有配置才能开始生效

/**
 * Indicates that a component is eligible for registration when one or more
 * {@linkplain #value specified profiles} are active.
 *
 * <p>A <em>profile</em> is a named logical grouping that may be activated
 * programmatically via {@link ConfigurableEnvironment#setActiveProfiles} or declaratively
 * by setting the {@link AbstractEnvironment#ACTIVE_PROFILES_PROPERTY_NAME
 * spring.profiles.active} property as a JVM system property, as an
 * environment variable, or as a Servlet context parameter in {@code web.xml}
 * for web applications. Profiles may also be activated declaratively in
 * integration tests via the {@code @ActiveProfiles} annotation.
 *
 * <p>The {@code @Profile} annotation may be used in any of the following ways:
 * <ul>
 * <li>as a type-level annotation on any class directly or indirectly annotated with
 * {@code @Component}, including {@link Configuration @Configuration} classes</li>
 * <li>as a meta-annotation, for the purpose of composing custom stereotype annotations</li>
 * <li>as a method-level annotation on any {@link Bean @Bean} method</li>
 * </ul>
 *
 * <p>If a {@code @Configuration} class is marked with {@code @Profile}, all of the
 * {@code @Bean} methods and {@link Import @Import} annotations associated with that class
 * will be bypassed unless one or more of the specified profiles are active. A profile
 * string may contain a simple profile name (for example {@code "p1"}) or a profile
 * expression. A profile expression allows for more complicated profile logic to be
 * expressed, for example {@code "p1 & p2"}. See {@link Profiles#of(String...)} for more
 * details about supported formats.
 *
 * <p>This is analogous to the behavior in Spring XML: if the {@code profile} attribute of
 * the {@code beans} element is supplied e.g., {@code <beans profile="p1,p2">}, the
 * {@code beans} element will not be parsed unless at least profile 'p1' or 'p2' has been
 * activated. Likewise, if a {@code @Component} or {@code @Configuration} class is marked
 * with {@code @Profile({"p1", "p2"})}, that class will not be registered or processed unless
 * at least profile 'p1' or 'p2' has been activated.
 *
 * <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.
 *
 * <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.
 *
 * @author Chris Beams
 * @author Phillip Webb
 * @author Sam Brannen
 * @since 3.1
 * @see ConfigurableEnvironment#setActiveProfiles
 * @see ConfigurableEnvironment#setDefaultProfiles
 * @see AbstractEnvironment#ACTIVE_PROFILES_PROPERTY_NAME
 * @see AbstractEnvironment#DEFAULT_PROFILES_PROPERTY_NAME
 * @see Conditional
 * @see org.springframework.test.context.ActiveProfiles
 */
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(ProfileCondition.class)
public @interface Profile {

    /**
     * The set of profiles for which the annotated component should be registered.
     */
    String[] value();

}

@Profile现在用的很少，配置环境

三种设置方式：

• 可以通过ConfigurableEnvironment.setActiveProfiles()以编程的方式激活

• 可以通过AbstractEnvironment.ACTIVE_PROFILES_PROPERTY_NAME (spring.profiles.active )属性设置为

  JVM属性

• 作为环境变量，或作为web.xml 应用程序的Servlet 上下文参数。也可以通过@ActiveProfiles 注解在集成测试中以声明方式激活配置文件。