【Spring源码分析】10-Environment

Environment扩展了PropertyResolver接口，定义了代表当前应用程序所处的运行环境的方法。

    public interface Environment extends PropertyResolver {
       String[] getActiveProfiles();//显示激活的运行环境
       String[] getDefaultProfiles();//默认的运行环境
       boolean acceptsProfiles(String... profiles);//有一个存在返回true
    }

ConfigurableEnvironment定义了可以设置profiles并提供PropertySource的方法。

    public interface ConfigurableEnvironment extends Environment, ConfigurablePropertyResolver {
       void setActiveProfiles(String... profiles);
       void addActiveProfile(String profile);
       void setDefaultProfiles(String... profiles);
       MutablePropertySources getPropertySources();
       Map<String, Object> getSystemEnvironment();
       Map<String, Object> getSystemProperties();
       void merge(ConfigurableEnvironment parent);
    }

AbstractEnvironment作为实现了ConfigurableEnvironment的基类，封装了接口所有方法的实现。

    private final Set<String> activeProfiles = new LinkedHashSet<>();
    private final Set<String> defaultProfiles = new LinkedHashSet<>(getReservedDefaultProfiles());
    //数据源
    private final MutablePropertySources propertySources = new MutablePropertySources(this.logger);
    //ConfigurablePropertyResolver接口方法都委托此对象完成
    private final ConfigurablePropertyResolver propertyResolver = new PropertySourcesPropertyResolver(this.propertySources);

构造函数中调用了customizePropertySources()完成初始化，这个方法需要子类覆盖填充propertySources。

    public AbstractEnvironment() {
    	customizePropertySources(this.propertySources);
    	if (logger.isDebugEnabled()) {
    		logger.debug("Initialized " + getClass().getSimpleName() + " with PropertySources " + this.propertySources);
    	}
    }

StandardEnvironment中添加了一个name=systemProperties的MapPropertySource和name=systemEnvironment的SystemEnvironmentPropertySource，分别提供对系统属性和环境变量的访问。

    public class StandardEnvironment extends AbstractEnvironment {
       public static final String SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME = "systemEnvironment";
       public static final String SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME = "systemProperties";
       @Override
       protected void customizePropertySources(MutablePropertySources propertySources) {
          propertySources.addLast(new MapPropertySource(SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME, getSystemProperties()));
          propertySources.addLast(new SystemEnvironmentPropertySource(SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME, getSystemEnvironment()));
       }
    }

StandardServletEnvironment中添加了两个站位的StubPropertySource分别代表提供访问ServletConfig和ServletContext。当调用initPropertySources()方法的时候会用参数传过来的servletContext和servletConfig替换掉站位StubPropertySource。

    public class StandardServletEnvironment extends StandardEnvironment implements ConfigurableWebEnvironment {
       public static final String SERVLET_CONTEXT_PROPERTY_SOURCE_NAME = "servletContextInitParams";
       public static final String SERVLET_CONFIG_PROPERTY_SOURCE_NAME = "servletConfigInitParams";
       public static final String JNDI_PROPERTY_SOURCE_NAME = "jndiProperties";
       @Override
       protected void customizePropertySources(MutablePropertySources propertySources) {
          propertySources.addLast(new StubPropertySource(SERVLET_CONFIG_PROPERTY_SOURCE_NAME));
          propertySources.addLast(new StubPropertySource(SERVLET_CONTEXT_PROPERTY_SOURCE_NAME));
          if (JndiLocatorDelegate.isDefaultJndiEnvironmentAvailable()) {
             propertySources.addLast(new JndiPropertySource(JNDI_PROPERTY_SOURCE_NAME));
          }
          super.customizePropertySources(propertySources);
       }
       @Override
       public void initPropertySources(@Nullable ServletContext servletContext, @Nullable ServletConfig servletConfig) {
          WebApplicationContextUtils.initServletPropertySources(getPropertySources(), servletContext, servletConfig);
       }
    }