文章目录
Spring的Environment接口有两个关键的作用：1. Profile， 2.properties。可以看下该接口的定义：
public interface Environment extends PropertyResolver { /** * Return the set of profiles explicitly made active for this environment. Profiles * are used for creating logical groupings of bean definitions to be registered * conditionally, for example based on deployment environment. Profiles can be * activated by setting {@linkplain AbstractEnvironment#ACTIVE_PROFILES_PROPERTY_NAME * "spring.profiles.active"} as a system property or by calling * {@link ConfigurableEnvironment#setActiveProfiles(String...)}. * <p>If no profiles have explicitly been specified as active, then any * {@linkplain #getDefaultProfiles() default profiles} will automatically be activated. * @see #getDefaultProfiles * @see ConfigurableEnvironment#setActiveProfiles * @see AbstractEnvironment#ACTIVE_PROFILES_PROPERTY_NAME */ String[] getActiveProfiles(); /** * Return the set of profiles to be active by default when no active profiles have * been set explicitly. * @see #getActiveProfiles * @see ConfigurableEnvironment#setDefaultProfiles * @see AbstractEnvironment#DEFAULT_PROFILES_PROPERTY_NAME */ String[] getDefaultProfiles(); /** * Return whether one or more of the given profiles is active or, in the case of no * explicit active profiles, whether one or more of the given profiles is included in * the set of default profiles. If a profile begins with '!' the logic is inverted, * i.e. the method will return {@code true} if the given profile is <em>not</em> active. * For example, {@code env.acceptsProfiles("p1", "!p2")} will return {@code true} if * profile 'p1' is active or 'p2' is not active. * @throws IllegalArgumentException if called with zero arguments * or if any profile is {@code null}, empty, or whitespace only * @see #getActiveProfiles * @see #getDefaultProfiles * @see #acceptsProfiles(Profiles) * @deprecated as of 5.1 in favor of {@link #acceptsProfiles(Profiles)} */ @Deprecated boolean acceptsProfiles(String... profiles); /** * Return whether the {@linkplain #getActiveProfiles() active profiles} * match the given {@link Profiles} predicate. */ boolean acceptsProfiles(Profiles profiles); }
它继承了PropertyResolver：
public interface PropertyResolver { /** * Return whether the given property key is available for resolution, * i.e. if the value for the given key is not {@code null}. */ boolean containsProperty(String key); /** * Return the property value associated with the given key, * or {@code null} if the key cannot be resolved. * @param key the property name to resolve * @see #getProperty(String, String) * @see #getProperty(String, Class) * @see #getRequiredProperty(String) */ @Nullable String getProperty(String key); /** * Return the property value associated with the given key, or * {@code defaultValue} if the key cannot be resolved. * @param key the property name to resolve * @param defaultValue the default value to return if no value is found * @see #getRequiredProperty(String) * @see #getProperty(String, Class) */ String getProperty(String key, String defaultValue); /** * Return the property value associated with the given key, * or {@code null} if the key cannot be resolved. * @param key the property name to resolve * @param targetType the expected type of the property value * @see #getRequiredProperty(String, Class) */ @Nullable <T> T getProperty(String key, Class<T> targetType); /** * Return the property value associated with the given key, * or {@code defaultValue} if the key cannot be resolved. * @param key the property name to resolve * @param targetType the expected type of the property value * @param defaultValue the default value to return if no value is found * @see #getRequiredProperty(String, Class) */ <T> T getProperty(String key, Class<T> targetType, T defaultValue); /** * Return the property value associated with the given key (never {@code null}). * @throws IllegalStateException if the key cannot be resolved * @see #getRequiredProperty(String, Class) */ String getRequiredProperty(String key) throws IllegalStateException; /** * Return the property value associated with the given key, converted to the given * targetType (never {@code null}). * @throws IllegalStateException if the given key cannot be resolved */ <T> T getRequiredProperty(String key, Class<T> targetType) throws IllegalStateException; /** * Resolve ${...} placeholders in the given text, replacing them with corresponding * property values as resolved by {@link #getProperty}. Unresolvable placeholders with * no default value are ignored and passed through unchanged. * @param text the String to resolve * @return the resolved String (never {@code null}) * @throws IllegalArgumentException if given text is {@code null} * @see #resolveRequiredPlaceholders * @see org.springframework.util.SystemPropertyUtils#resolvePlaceholders(String) */ String resolvePlaceholders(String text); /** * Resolve ${...} placeholders in the given text, replacing them with corresponding * property values as resolved by {@link #getProperty}. Unresolvable placeholders with * no default value will cause an IllegalArgumentException to be thrown. * @return the resolved String (never {@code null}) * @throws IllegalArgumentException if given text is {@code null} * or if any placeholders are unresolvable * @see org.springframework.util.SystemPropertyUtils#resolvePlaceholders(String, boolean) */ String resolveRequiredPlaceholders(String text) throws IllegalArgumentException; }
Profile是一个Bean的逻辑分组，只有在给定的配置文件处于活动状态时，才会在容器中注册。
Properties主要用来从各种源：属性文件、JVM系统属性、系统环境变量、JNDI、servlet上下文参数、特殊属性对象、映射对象等读取属性的定义。
Profiles
在开发中，我们可以需要在不同的环境定义不同的配置，例如：
- 在开发中处理内存中的数据源，而不是在QA或生产中从JNDI中查找相同的数据源。
- 仅在将应用程序部署到性能环境中时注册监控基础结构。
- 为客户A和客户B部署注册定制的bean实现。
假如我们有两个数据源，一个是在测试环境使用，一个是在线上环境使用，则可以通过profile来指定不同的环境。如下所示：
@Configuration @Profile("development") public class StandaloneDataConfig { @Bean public DataSource dataSource() { return new EmbeddedDatabaseBuilder() .setType(EmbeddedDatabaseType.HSQL) .addScript("classpath:com/bank/config/sql/schema.sql") .addScript("classpath:com/bank/config/sql/test-data.sql") .build(); } }
@Configuration @Profile("production") public class JndiDataConfig { @Bean(destroyMethod="") public DataSource dataSource() throws Exception { Context ctx = new InitialContext(); return (DataSource) ctx.lookup("java:comp/env/jdbc/datasource"); } }
@Profile里面的表达式可以是简单的字符串，也可以支持运算符，如：
- ! 逻辑非
- & 逻辑与
- | 逻辑或
可以将@Profile用作元注解，以创建自定义组合注解。以下示例定义了一个自定义的@Production注解，您可以将其用作@Profile（“production”）的替换：
@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Profile("production") public @Interface Production { }
@Profile也可以用在方法级别用来包含一个特殊的bean或者配置类。如下所示：
@Configuration public class AppConfig { @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("dataSource") @Profile("production") public DataSource jndiDataSource() throws Exception { Context ctx = new InitialContext(); return (DataSource) ctx.lookup("java:comp/env/jdbc/datasource"); } }
Profiles在XML中使用
可以在XML中使用profile属性，如下所示：
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:jdbc="http://www.springframework.org/schema/jdbc" xmlns:jee="http://www.springframework.org/schema/jee" xsi:schemaLocation="..."> <!-- other bean definitions --> <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"/> </jdbc:embedded-database> </beans> <beans profile="production"> <jee:jndi-lookup id="dataSource" jndi-name="java:comp/env/jdbc/datasource"/> </beans> </beans>
激活Profile
上面我们定义好了Profile，但是怎么激活他们？
激活一个概要文件可以用几种方法完成，但最简单的方法是通过应用程序上下文提供的环境API以编程方式完成。以下示例显示了如何执行此操作：
public static void main(String[] args) { AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(); ctx.getEnvironment().setActiveProfiles("development"); ctx.register(AppConfig.class, StandaloneDataConfig.class, JndiDataConfig.class); ctx.refresh(); }
此外，还可以通过spring.profiles.active属性声明性地激活概要文件，该属性可以通过系统环境变量、jvm系统属性、web.xml中的servlet上下文参数指定，甚至可以作为JNDI中的条目指定.
如下所示：
-Dspring.profiles.active=“profile1,profile2”
你也可以同时激活多个pofile
ctx.getEnvironment().setActiveProfiles(“profile1”, “profile2”);
默认Profile
默认的Profile表示该Profile默认被激活，如下所示：
@Configuration @Profile("default") public class DefaultDataConfig { @Bean public DataSource dataSource() { return new EmbeddedDatabaseBuilder() .setType(EmbeddedDatabaseType.HSQL) .addScript("classpath:com/bank/config/sql/schema.sql") .build(); } }
如果没有Profile被激活，那么dataSource就会被创建，你可以看成创建bean的默认方式。如果其他的Profile被激活了，那么默认的Profile就不会被使用。
您可以在环境中使用SetDefaultProfiles（）更改默认profile的名称，或者声明性地使用spring.profiles.default属性更改默认概要文件的名称。
PropertySource
下面是使用PropertySource的例子：
public static void main(String[] args) { ApplicationContext ctx = new GenericApplicationContext(); Environment env = ctx.getEnvironment(); boolean containsMyProperty = env.containsProperty("my-property"); System.out.println("Does my environment contain the 'my-property' property? " + containsMyProperty); }
这里Spring查询是否定义了my-property属性，这里的StandardEnvironment定义了两组PropertySource对象进行查询，
/** System environment property source name: {@value}. */ public static final String SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME = "systemEnvironment"; /** JVM system properties property source name: {@value}. */ public static final String SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME = "systemProperties";
一个表示一组JVM系统属性（System.GetProperties（）），另一个表示一组系统环境变量（System.getEnv（））。
对于常见的StandardServletEnvironment，property的查询优先级如下：
- ServletConfig参数（如果适用-例如，对于DispatcherServlet上下文）
- ServletContext参数（web.xml context-param 项）
- JNDI环境变量（Java:COMP/Env/条目）
- JVM系统属性（-d命令行参数）
- JVM系统环境（操作系统环境变量）
使用@PropertySource
@PropertySource注解提供了方便和声明式的机制为Spring的添加PropertySource.
下面的@Configuration类使用@PropertySource 来调用testBean.getName() 返回 myTestBean：
@Configuration @PropertySource("classpath:app.properties") public class PropertiesConfig { @Autowired Environment env; @Bean public TestBean testBean() { TestBean testBean = new TestBean(); testBean.setName(env.getProperty("testbean.name")); return testBean; } }
@Propertysource资源位置中存在的任何$…占位符将根据已针对环境注册的属性源集进行解析，如下示例所示：
@PropertySource("classpath:/com/${my.placeholder:default/path}/app.properties")
假设my.placeholder存在于已注册的某个属性源中（例如，系统属性或环境变量），则将占位符解析为相应的值。如果不是，则default/path用作默认值。如果未指定默认值且无法解析属性，则将引发IllegalArgumentException。
