application.yml 的加载流程分析
application.yml 文件对于 Spring Boot 来说是核心配置文件，至关重要，那么，该文件是如何加载到内存的呢？需要从启动类的 run()方法开始跟踪。
1. 启动方法 run()跟踪
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
//org.springframework.boot.SpringApplication#run(java.lang.Class<?>, java.lang.String...)
public static ConfigurableApplicationContext run(Class<?> primarySource, String... args) {
return run(new Class<?>[] {
primarySource }, args);
}
//org.springframework.boot.SpringApplication#run(java.lang.Class<?>[], java.lang.String[])
public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {
return new SpringApplication(primarySources).run(args);
}
直接跟SpringApplication的run方法：
/**
* Run the Spring application, creating and refreshing a new
* {@link ApplicationContext}.
* @param args the application arguments (usually passed from a Java main method)
* @return a running {@link ApplicationContext}
*/
//org.springframework.boot.SpringApplication#run(java.lang.String...)
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
configureHeadlessProperty();
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.starting();
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
//准备运行环境
ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
configureIgnoreBeanInfo(environment);
Banner printedBanner = printBanner(environment);
context = createApplicationContext();
exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
new Class[] {
ConfigurableApplicationContext.class }, context);
prepareContext(context, environment, listeners, applicationArguments, printedBanner);
refreshContext(context);
afterRefresh(context, applicationArguments);
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
}
listeners.started(context);
callRunners(context, applicationArguments);
}
catch (Throwable ex) {
handleRunFailure(context, ex, exceptionReporters, listeners);
throw new IllegalStateException(ex);
}
try {
listeners.running(context);
}
catch (Throwable ex) {
handleRunFailure(context, ex, exceptionReporters, null);
throw new IllegalStateException(ex);
}
return context;
}
2. 准备运行环境
看prepareEnvironment方法：
//org.springframework.boot.SpringApplication#prepareEnvironment
private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments) {
// Create and configure the environment
ConfigurableEnvironment environment = getOrCreateEnvironment();
configureEnvironment(environment, applicationArguments.getSourceArgs());
ConfigurationPropertySources.attach(environment);
//为准备过程添加监听
listeners.environmentPrepared(environment);
bindToSpringApplication(environment);
if (!this.isCustomEnvironment) {
environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,
deduceEnvironmentClass());
}
ConfigurationPropertySources.attach(environment);
return environment;
}
3. 为准备过程添加监听
//org.springframework.boot.SpringApplicationRunListeners#environmentPrepared
public void environmentPrepared(ConfigurableEnvironment environment) {
for (SpringApplicationRunListener listener : this.listeners) {
listener.environmentPrepared(environment);
}
}
DEBUG：
//org.springframework.boot.context.event.EventPublishingRunListener#environmentPrepared
public void environmentPrepared(ConfigurableEnvironment environment) {
//广播环境准备事件
this.initialMulticaster
.multicastEvent(new ApplicationEnvironmentPreparedEvent(this.application, this.args, environment));
}
4. 广播环境准备事件
//org.springframework.context.event.SimpleApplicationEventMulticaster#multicastEvent(org.springframework.context.ApplicationEvent)
public void multicastEvent(ApplicationEvent event) {
multicastEvent(event, resolveDefaultEventType(event));
}
//org.springframework.context.event.SimpleApplicationEventMulticaster#multicastEvent(org.springframework.context.ApplicationEvent, org.springframework.core.ResolvableType)
public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) {
ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));
Executor executor = getTaskExecutor();
for (ApplicationListener<?> listener : getApplicationListeners(event, type)) {
if (executor != null) {
//触发监听器
executor.execute(() -> invokeListener(listener, event));
}
else {
//触发监听器
invokeListener(listener, event);
}
}
}
5. 触发监听器
//org.springframework.context.event.SimpleApplicationEventMulticaster#invokeListener
protected void invokeListener(ApplicationListener<?> listener, ApplicationEvent event) {
ErrorHandler errorHandler = getErrorHandler();
if (errorHandler != null) {
try {
doInvokeListener(listener, event);
}
catch (Throwable err) {
errorHandler.handleError(err);
}
}
else {
doInvokeListener(listener, event);
}
}
//org.springframework.context.event.SimpleApplicationEventMulticaster#doInvokeListener
private void doInvokeListener(ApplicationListener listener, ApplicationEvent event) {
try {
listener.onApplicationEvent(event);
}
catch (ClassCastException ex) {
String msg = ex.getMessage();
if (msg == null || matchesClassCastMessage(msg, event.getClass())) {
// Possibly a lambda-defined listener which we could not resolve the generic event type for
// -> let's suppress the exception and just log a debug message.
Log logger = LogFactory.getLog(getClass());
if (logger.isTraceEnabled()) {
logger.trace("Non-matching event type for listener: " + listener, ex);
}
}
else {
throw ex;
}
}
}
//org.springframework.boot.context.config.ConfigFileApplicationListener#onApplicationEvent
public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof ApplicationEnvironmentPreparedEvent) {
//环境准备事件
onApplicationEnvironmentPreparedEvent((ApplicationEnvironmentPreparedEvent) event);
}
if (event instanceof ApplicationPreparedEvent) {
onApplicationPreparedEvent(event);
}
}
//org.springframework.boot.context.config.ConfigFileApplicationListener#onApplicationEnvironmentPreparedEvent
private void onApplicationEnvironmentPreparedEvent(ApplicationEnvironmentPreparedEvent event) {
List<EnvironmentPostProcessor> postProcessors = loadPostProcessors();
postProcessors.add(this);
AnnotationAwareOrderComparator.sort(postProcessors);
for (EnvironmentPostProcessor postProcessor : postProcessors) {
postProcessor.postProcessEnvironment(event.getEnvironment(), event.getSpringApplication());
}
}
DEBUG：
主要关注配置文件应用监听：
//org.springframework.boot.context.config.ConfigFileApplicationListener#postProcessEnvironment
public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
addPropertySources(environment, application.getResourceLoader());
}
//org.springframework.boot.context.config.ConfigFileApplicationListener#addPropertySources
protected void addPropertySources(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {
RandomValuePropertySource.addToEnvironment(environment);
//load：加载配置文件
new Loader(environment, resourceLoader).load();
}
6. 加载配置文件
//org.springframework.boot.context.config.ConfigFileApplicationListener.Loader#load()
void load() {
FilteredPropertySource.apply(this.environment, DEFAULT_PROPERTIES, LOAD_FILTERED_PROPERTY,
(defaultProperties) -> {
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 (isDefaultProfile(profile)) {
addProfileToEnvironment(profile.getName());
}
//根据指定profile加载
load(profile, this::getPositiveProfileFilter,
addToLoaded(MutablePropertySources::addLast, false));
this.processedProfiles.add(profile);
}
//未指定profile加载
load(null, this::getNegativeProfileFilter, addToLoaded(MutablePropertySources::addFirst, true));
addLoadedPropertySources();
applyActiveProfiles(defaultProperties);
});
}
//org.springframework.boot.context.config.ConfigFileApplicationListener.Loader#load(org.springframework.boot.context.config.ConfigFileApplicationListener.Profile, org.springframework.boot.context.config.ConfigFileApplicationListener.DocumentFilterFactory, org.springframework.boot.context.config.ConfigFileApplicationListener.DocumentConsumer)
private void load(Profile profile, DocumentFilterFactory filterFactory, DocumentConsumer consumer) {
getSearchLocations().forEach((location) -> {
boolean isDirectory = location.endsWith("/");
Set<String> names = isDirectory ? getSearchNames() : NO_SEARCH_NAMES;
//继续走load
names.forEach((name) -> load(location, name, profile, filterFactory, consumer));
});
}
//org.springframework.boot.context.config.ConfigFileApplicationListener.Loader#load(java.lang.String, java.lang.String, org.springframework.boot.context.config.ConfigFileApplicationListener.Profile, org.springframework.boot.context.config.ConfigFileApplicationListener.DocumentFilterFactory, org.springframework.boot.context.config.ConfigFileApplicationListener.DocumentConsumer)
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;
}
}
throw new IllegalStateException("File extension of config file location '" + location
+ "' is not known to any PropertySourceLoader. If the location is meant to reference "
+ "a directory, it must end in '/'");
}
Set<String> processed = new HashSet<>();
for (PropertySourceLoader loader : this.propertySourceLoaders) {
for (String fileExtension : loader.getFileExtensions()) {
//fileExtension ：文件的扩展名
if (processed.add(fileExtension)) {
loadForFileExtension(loader, location + name, "." + fileExtension, profile, filterFactory,
consumer);
}
}
}
}
DEBUG：
//org.springframework.boot.context.config.ConfigFileApplicationListener.Loader#loadForFileExtension
private void loadForFileExtension(PropertySourceLoader loader, String prefix, String fileExtension,
Profile profile, DocumentFilterFactory filterFactory, DocumentConsumer consumer) {
DocumentFilter defaultFilter = filterFactory.getDocumentFilter(null);
DocumentFilter profileFilter = filterFactory.getDocumentFilter(profile);
if (profile != null) {
// Try profile-specific file & profile section in profile file (gh-340)
String profileSpecificFile = prefix + "-" + profile + fileExtension;
load(loader, profileSpecificFile, profile, defaultFilter, consumer);
load(loader, profileSpecificFile, profile, profileFilter, consumer);
// Try profile specific sections in files we've already processed
for (Profile processedProfile : this.processedProfiles) {
if (processedProfile != null) {
String previouslyLoaded = prefix + "-" + processedProfile + fileExtension;
load(loader, previouslyLoaded, profile, profileFilter, consumer);
}
}
}
// Also try the profile-specific section (if any) of the normal file
// 走这
load(loader, prefix + fileExtension, profile, profileFilter, consumer);
}
//org.springframework.boot.context.config.ConfigFileApplicationListener.Loader#load(org.springframework.boot.env.PropertySourceLoader, java.lang.String, org.springframework.boot.context.config.ConfigFileApplicationListener.Profile, org.springframework.boot.context.config.ConfigFileApplicationListener.DocumentFilter, org.springframework.boot.context.config.ConfigFileApplicationListener.DocumentConsumer)
private void load(PropertySourceLoader loader, String location, Profile profile, DocumentFilter filter,
DocumentConsumer consumer) {
Resource[] resources = getResources(location);
for (Resource resource : resources) {
try {
if (resource == null || !resource.exists()) {
if (this.logger.isTraceEnabled()) {
StringBuilder description = getDescription("Skipped missing config ", location, resource,
profile);
this.logger.trace(description);
}
continue;
}
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);
}
continue;
}
String name = "applicationConfig: [" + getLocationName(location, resource) + "]";
//加载文档
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);
}
continue;
}
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) {
StringBuilder description = getDescription("Failed to load property source from ", location,
resource, profile);
throw new IllegalStateException(description.toString(), ex);
}
}
}
//org.springframework.boot.context.config.ConfigFileApplicationListener.Loader#loadDocuments
private List<Document> loadDocuments(PropertySourceLoader loader, String name, Resource resource)
throws IOException {
DocumentsCacheKey cacheKey = new DocumentsCacheKey(loader, resource);
List<Document> documents = this.loadDocumentsCache.get(cacheKey);
if (documents == null) {
//加载
List<PropertySource<?>> loaded = loader.load(name, resource);
documents = asDocuments(loaded);
this.loadDocumentsCache.put(cacheKey, documents);
}
return documents;
}
DEBUG：
public class YamlPropertySourceLoader implements PropertySourceLoader {
@Override
public String[] getFileExtensions() {
return new String[] {
"yml", "yaml" };
}
@Override
public List<PropertySource<?>> load(String name, Resource resource) throws IOException {
if (!ClassUtils.isPresent("org.yaml.snakeyaml.Yaml", null)) {
throw new IllegalStateException(
"Attempted to load " + name + " but snakeyaml was not found on the classpath");
}
List<Map<String, Object>> loaded = new OriginTrackedYamlLoader(resource).load();
if (loaded.isEmpty()) {
return Collections.emptyList();
}
List<PropertySource<?>> propertySources = new ArrayList<>(loaded.size());
for (int i = 0; i < loaded.size(); i++) {
String documentNumber = (loaded.size() != 1) ? " (document #" + i + ")" : "";
propertySources.add(new OriginTrackedMapPropertySource(name + documentNumber,
Collections.unmodifiableMap(loaded.get(i)), true));
}
return propertySources;
}
}
DEBUG
