Spring Boot常用功能Profile详解

入口

相关逻辑的入口是listener类：ConfigFileApplicationListener，当容器广播器触发ApplicationEnvironmentPreparedEvent事件时，ConfigFileApplicationListener会收到广播器的通知，进而执行onApplicationEnvironmentPreparedEvent方法

入口处代码：

	@Override
	public void onApplicationEvent(ApplicationEvent event) {
		if (event instanceof ApplicationEnvironmentPreparedEvent) {
			onApplicationEnvironmentPreparedEvent((ApplicationEnvironmentPreparedEvent) event);
		}
		if (event instanceof ApplicationPreparedEvent) {
			onApplicationPreparedEvent(event);
		}
	}

接下来onApplicationEnvironmentPreparedEvent方法会加载容器中的EnvironmentPostProcessor并进行遍历，调用他们的postProcessEnvironment方法，我们可以看一下此时的PostProcessor有哪些：

我们发现ConfigFileApplicationListener本身也是其中一个PostProcessor :)

我们直接进入ConfigFileApplicationListener的postProcessEnvironment方法，它会调用一个addPropertySources方法

	protected void addPropertySources(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {
		RandomValuePropertySource.addToEnvironment(environment);
		new Loader(environment, resourceLoader).load();
	}

随机属性值部分暂且不表，我们看下loader.load方法

		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();
		}

load方法的重点逻辑-initializeProfiles()

private void initializeProfiles() {
	// The default profile for these purposes is represented as null. We add it
	// first so that it is processed first and has lowest priority.
	this.profiles.add(null);
	Set<Profile> activatedViaProperty = getProfilesActivatedViaProperty();
	this.profiles.addAll(getOtherActiveProfiles(activatedViaProperty));
	// Any pre-existing active profiles set via property sources (e.g.
	// System properties) take precedence over those added in config files.
	addActiveProfiles(activatedViaProperty);
	if (this.profiles.size() == 1) { // only has null profile
		for (String defaultProfileName : this.environment.getDefaultProfiles()) {
			Profile defaultProfile = new Profile(defaultProfileName, true);
			this.profiles.add(defaultProfile);
		}
	}
}

add(null) 可以处理application.properties/yml，接下来getProfilesActivatedViaProperty方法会从spring.profiles.active和spring.profiles.include配置中读取激活的profile~(这两者也是相对常用的配置)；再接下来会判断profiles大小是否为1，是的话会添加一个default profile，如图所示：

这也解释了为什么spring.profiles.default必须定义在其他属性源（命令行启动参数），因为这时候分散文件属性元还没有被解析到！

回到load方法，如果profiles不为空，就会进行while遍历，对其调用另外一个load方法：

（load-number2方法）：

		private void load(Profile profile, DocumentFilterFactory filterFactory, DocumentConsumer consumer) {
			getSearchLocations().forEach((location) -> {
				boolean isFolder = location.endsWith("/");
				Set<String> names = isFolder ? getSearchNames() : NO_SEARCH_NAMES;
				names.forEach((name) -> load(location, name, profile, filterFactory, consumer));
			});
		}

我们可以看到还会调用到另一个load方法

（load-number3方法）：

private void load(String location, String name, Profile profile, DocumentFilterFactory filterFactory,
		DocumentConsumer consumer) {
	if (!StringUtils.hasText(name)) {
		for (PropertySourceLoader loader : this.propertySourceLoaders) {
			if (canLoadFileExtension(loader, location)) {
				load(loader, location, profile, filterFactory.getDocumentFilter(profile), consumer);
				return;
			}
		}
	}
	Set<String> processed = new HashSet<>();
	for (PropertySourceLoader loader : this.propertySourceLoaders) {
		for (String fileExtension : loader.getFileExtensions()) {
			if (processed.add(fileExtension)) {
				loadForFileExtension(loader, location + name, "." + fileExtension, profile, filterFactory,
						consumer);
			}
		}
	}
}

这里的propertySourceLoaders包括：

是不是很熟悉？这就是properties和yaml分别对应的PropertySourceLoader~

下面代码会调用loadForFileExtension方法，而这个方法又会调用新的load方法（）：

（load-number4方法）：

private void load(PropertySourceLoader loader, String location, Profile profile, DocumentFilter filter,
		DocumentConsumer consumer) {
	try {
		Resource resource = this.resourceLoader.getResource(location);
		if (resource == null || !resource.exists()) {
			if (this.logger.isTraceEnabled()) {
				StringBuilder description = getDescription("Skipped missing config ", location, resource,
						profile);
				this.logger.trace(description);
			}
			return;
		}
		if (!StringUtils.hasText(StringUtils.getFilenameExtension(resource.getFilename()))) {
			if (this.logger.isTraceEnabled()) {
				StringBuilder description = getDescription("Skipped empty config extension ", location,
						resource, profile);
				this.logger.trace(description);
			}
			return;
		}
		String name = "applicationConfig: [" + location + "]";
		List<Document> documents = loadDocuments(loader, name, resource);
		if (CollectionUtils.isEmpty(documents)) {
			if (this.logger.isTraceEnabled()) {
				StringBuilder description = getDescription("Skipped unloaded config ", location, resource,
						profile);
				this.logger.trace(description);
			}
			return;
		}
		List<Document> loaded = new ArrayList<>();
		for (Document document : documents) {
			if (filter.match(document)) {
				addActiveProfiles(document.getActiveProfiles());
				addIncludedProfiles(document.getIncludeProfiles());
				loaded.add(document);
			}
		}
		Collections.reverse(loaded);
		if (!loaded.isEmpty()) {
			loaded.forEach((document) -> consumer.accept(profile, document));
			if (this.logger.isDebugEnabled()) {
				StringBuilder description = getDescription("Loaded config file ", location, resource, profile);
				this.logger.debug(description);
			}
		}
	}
	catch (Exception ex) {
		throw new IllegalStateException("Failed to load property " + "source from location '" + location + "'",
				ex);
	}
}

这个方法会读取application-profile.properties/yaml文件，并加载文件内激活的profile（如果有的话）

到这里已经读取到了所有的配置信息，主逻辑大概结束了，还差最后一个步骤：addLoadedPropertySources：

		private void addLoadedPropertySources() {
			MutablePropertySources destination = this.environment.getPropertySources();
			List<MutablePropertySources> loaded = new ArrayList<>(this.loaded.values());
			Collections.reverse(loaded);
			String lastAdded = null;
			Set<String> added = new HashSet<>();
			for (MutablePropertySources sources : loaded) {
				for (PropertySource<?> source : sources) {
					if (added.add(source.getName())) {
						addLoadedPropertySource(destination, lastAdded, source);
						lastAdded = source.getName();
					}
				}
			}
		}

这里会将所有属性加入到“destination”，即environment.getPropertySources()，到这里，加载配置属性的逻辑就完成了。

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