SpringBoot environment

Environment

Environment 是Spring的當前運行環境的抽象定義，一般包含兩類：profile和properties。具體的屬性實現體現在 PropertyResolver 接口。

prepareEnvironment

在SpringBoot啓動流程中，會初始化對應的環境。
SpringApplication#prepareEnvironment

	private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,
			ApplicationArguments applicationArguments) {
		// Create and configure the environment
		ConfigurableEnvironment environment = getOrCreateEnvironment();
		configureEnvironment(environment, applicationArguments.getSourceArgs());
		listeners.environmentPrepared(environment);
		bindToSpringApplication(environment);
		if (!this.isCustomEnvironment) {
			environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,
					deduceEnvironmentClass());
		}
		ConfigurationPropertySources.attach(environment);
		return environment;
	}

創建Environment

	private ConfigurableEnvironment getOrCreateEnvironment() {
		if (this.environment != null) {
			return this.environment;
		}
		switch (this.webApplicationType) {
		case SERVLET:
			return new StandardServletEnvironment();
		case REACTIVE:
			return new StandardReactiveWebEnvironment();
		default:
			return new StandardEnvironment();
		}
	}

最終生成對應的StandardServletEnvironment，StandardServletEnvironment通過父類的構造方法初始化AbstractEnvironment

	/**
	 * Create a new {@code Environment} instance, calling back to
	 * {@link #customizePropertySources(MutablePropertySources)} during construction to
	 * allow subclasses to contribute or manipulate {@link PropertySource} instances as
	 * appropriate.
	 * @see #customizePropertySources(MutablePropertySources)
	 */
	public AbstractEnvironment() {
		customizePropertySources(this.propertySources);
	}

	@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);
	}

	/** Servlet context init parameters property source name: {@value}. */
	public static final String SERVLET_CONTEXT_PROPERTY_SOURCE_NAME = "servletContextInitParams";

	/** Servlet config init parameters property source name: {@value}. */
	public static final String SERVLET_CONFIG_PROPERTY_SOURCE_NAME = "servletConfigInitParams";

	/** JNDI property source name: {@value}. */
	public static final String JNDI_PROPERTY_SOURCE_NAME = "jndiProperties";

最後再調用父類的

	protected void customizePropertySources(MutablePropertySources propertySources) {
		propertySources.addLast(
				new PropertiesPropertySource(SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME, getSystemProperties()));
		propertySources.addLast(
				new SystemEnvironmentPropertySource(SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME, getSystemEnvironment()));
	}

	/** 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";

加載完後，具體的初始化順序如下，優先servlet相關參數：

#configureEnvironment 加載配置

	protected void configureEnvironment(ConfigurableEnvironment environment, String[] args) {
		if (this.addConversionService) {
			ConversionService conversionService = ApplicationConversionService.getSharedInstance();
			environment.setConversionService((ConfigurableConversionService) conversionService);
		}
		configurePropertySources(environment, args);
		configureProfiles(environment, args);
	}

加載配置分爲兩步，加載property文件、加載profile文件。

configurePropertySources

	protected void configurePropertySources(ConfigurableEnvironment environment, String[] args) {
		MutablePropertySources sources = environment.getPropertySources();
		//如果指定了默認配置，則加載默認配置
		if (this.defaultProperties != null && !this.defaultProperties.isEmpty()) {
			sources.addLast(new MapPropertySource("defaultProperties", this.defaultProperties));
		}
		//加載命令行參數
		if (this.addCommandLineProperties && args.length > 0) {
			String name = CommandLinePropertySource.COMMAND_LINE_PROPERTY_SOURCE_NAME;
			if (sources.contains(name)) {
				PropertySource<?> source = sources.get(name);
				CompositePropertySource composite = new CompositePropertySource(name);
				composite.addPropertySource(
						new SimpleCommandLinePropertySource("springApplicationCommandLineArgs", args));
				composite.addPropertySource(source);
				sources.replace(name, composite);
			}
			else {
				sources.addFirst(new SimpleCommandLinePropertySource(args));
			}
		}
	}

加載profile

	protected void configureProfiles(ConfigurableEnvironment environment, String[] args) {
		environment.getActiveProfiles(); // ensure they are initialized
		// But these ones should go first (last wins in a property key clash)
		Set<String> profiles = new LinkedHashSet<>(this.additionalProfiles);
		profiles.addAll(Arrays.asList(environment.getActiveProfiles()));
		environment.setActiveProfiles(StringUtils.toStringArray(profiles));
	}

listeners.environmentPrepared(environment)

通知SpringBoot環境準備監聽器

listeners.environmentPrepared(environment);

對應的監聽器爲ConfigFileApplicationListener
ConfigFileApplicationListener#postProcessEnvironment

	@Override
	public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
		addPropertySources(environment, application.getResourceLoader());
	}
	
	protected void addPropertySources(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {
		RandomValuePropertySource.addToEnvironment(environment);
		new Loader(environment, resourceLoader).load();
	}

最終通過Loader類加載，解析文件，加載屬性

		public void load() {
			this.profiles = new LinkedList<>();
			this.processedProfiles = new LinkedList<>();
			this.activatedProfiles = false;
			this.loaded = new LinkedHashMap<>();
			initializeProfiles();
			while (!this.profiles.isEmpty()) {
				Profile profile = this.profiles.poll();
				if (profile != null && !profile.isDefaultProfile()) {
					addProfileToEnvironment(profile.getName());
				}
				load(profile, this::getPositiveProfileFilter, addToLoaded(MutablePropertySources::addLast, false));
				this.processedProfiles.add(profile);
			}
			resetEnvironmentProfiles(this.processedProfiles);
			load(null, this::getNegativeProfileFilter, addToLoaded(MutablePropertySources::addFirst, true));
			addLoadedPropertySources();
		}

配置文件加載如下

優先級由上到下，下面的配置會覆蓋上面的。

bindToSpringApplication(environment)

	/**
	 * Bind the environment to the {@link SpringApplication}.
	 * @param environment the environment to bind
	 */
	protected void bindToSpringApplication(ConfigurableEnvironment environment) {
		try {
			Binder.get(environment).bind("spring.main", Bindable.ofInstance(this));
		}
		catch (Exception ex) {
			throw new IllegalStateException("Cannot bind to SpringApplication", ex);
		}
	}