Spring - 注解驱动开发三切换环境

@Profile注解

Spring为我们提供的可以根据当前环境，动态的激活和切换一系列组件的功能。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。

接口类如下：

• 看一下Javadoc，什么都明白了。

/**
 * Indicates that a component is eligible for registration when one or more
 * {@linkplain #value specified profiles} are active.//看这句看这句看这句看这句
 *
 * <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.//这里说了四种方式
 *
 * <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. 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();

}

---

总结如下：

① 如果不加@Profile注解，则该bean在任何环境下都被注入；

    @Bean
    public Yellow yellow(){
        return new Yellow();
    }

---

② 如果指定了@Profile，则只有该环境被激活的时候bean才会被注入；

    @Profile("dev")
    @Bean("devDataSource")
    public DataSource dataSourceDev(@Value("${db.password}")String pwd) throws Exception{
        ComboPooledDataSource dataSource = new ComboPooledDataSource();
        dataSource.setUser(user);
        dataSource.setPassword(pwd);
        dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/xian");
        dataSource.setDriverClass(driverClass);
        return dataSource;
    }

---

③ 如果指定了@Profile(“default”)，那么默认环境下bean会被注入；

    @Profile("default")
    @Bean("testDataSource")
    public DataSource dataSourceTest(@Value("${db.password}")String pwd) throws Exception{
        ComboPooledDataSource dataSource = new ComboPooledDataSource();
        dataSource.setUser(user);
        dataSource.setPassword(pwd);
        dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/test");
        dataSource.setDriverClass(driverClass);
        return dataSource;
    }

---

④ 如果@Profile配置于类上，则该类下的bean想起作用，Spring激活的环境首先要与类配置@Profile指定的环境一致，其次再看类中方法上的@Profile注解配置。

@PropertySource("classpath:/dbconfig.properties")
@Profile("dev")
@Configuration
public class MainConfigOfProfile implements EmbeddedValueResolverAware{

    @Value("${db.user}")
    private String user;

    private StringValueResolver valueResolver;

    private String  driverClass;

    @Bean
    public Yellow yellow(){
        return new Yellow();
    }

    @Profile("default")
//  @Profile("test")
    @Bean("testDataSource")
    public DataSource dataSourceTest(@Value("${db.password}")String pwd) throws Exception{
        ComboPooledDataSource dataSource = new ComboPooledDataSource();
        dataSource.setUser(user);
        dataSource.setPassword(pwd);
        dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/test");
        dataSource.setDriverClass(driverClass);
        return dataSource;
    }

    @Profile("dev")
    @Bean("devDataSource")
    public DataSource dataSourceDev(@Value("${db.password}")String pwd) throws Exception{
        ComboPooledDataSource dataSource = new ComboPooledDataSource();
        dataSource.setUser(user);
        dataSource.setPassword(pwd);
        dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/xian");
        dataSource.setDriverClass(driverClass);
        return dataSource;
    }
}

---

激活环境的几种方式

① 虚拟机参数

---

② 代码激活

@Test
    public void test01(){
        //1、创建一个applicationContext
        AnnotationConfigApplicationContext applicationContext = 
                new AnnotationConfigApplicationContext();
        //2、设置需要激活的环境
        applicationContext.getEnvironment().setActiveProfiles("dev");
        //3、注册主配置类
        applicationContext.register(MainConfigOfProfile.class);
        //4、启动刷新容器
        applicationContext.refresh();

        String[] namesForType = applicationContext.getBeanNamesForType(DataSource.class);
        for (String string : namesForType) {
            System.out.println(string);
        }

        Yellow bean = applicationContext.getBean(Yellow.class);
        System.out.println(bean);
        applicationContext.close();
    }

---

③ web.xml

 <!-- 在上下文中设置profile的默认值 -->
  <context-param>
       <param-name>spring.profiles.default</param-name>
       <param-value>dev</param-value>
   </context-param>

 <servlet>
       <servlet-name>appServlet</servlet-name>
       <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
       <!-- 在servlet中设置profile的默认值 -->
       <init-param>
           <param-name>spring.profiles.default</param-name>
           <param-value>dev</param-value>
       </init-param>
       <load-on-startup>1</load-on-startup>
   </servlet>