今天小编给大家分享一下Springboot启动原理和自动配置原理是什么的相关知识点，内容详细，逻辑清晰，相信大部分人都还太了解这方面的知识，所以分享这篇文章给大家参考一下，希望大家阅读完这篇文章后有所收获，下面我们一起来了解一下吧。
启动原理
@SpringBootApplication
public class Start {
public static void main(String[] args) {
SpringApplication.run(Start.class, args);
}
}SpringApplication
1、初始化
public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {
return (new SpringApplication(primarySources)).run(args);
} public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
this.sources = new LinkedHashSet(); //
this.bannerMode = Mode.CONSOLE;// 控制banner
this.logStartupInfo = true;// 是否启动日志
this.addCommandLineProperties = true; // 读取命令行配置
this.addConversionService = true; //添加转换器
this.headless = true; //
this.registerShutdownHook = true; // 注册重启
this.additionalProfiles = Collections.emptySet();// 读取配置环境
this.isCustomEnvironment = false;// 是否是自定义环境
this.lazyInitialization = false; // 是否懒加载
this.applicationContextFactory = ApplicationContextFactory.DEFAULT;
this.applicationStartup = ApplicationStartup.DEFAULT; // ApplicationStartup DEFAULT = new DefaultApplicationStartup();
this.resourceLoader = resourceLoader;// 资源加载器
Assert.notNull(primarySources, "PrimarySources must not be null");
this.primarySources = new LinkedHashSet(Arrays.asList(primarySources)); // 主程序
this.webApplicationType = WebApplicationType.deduceFromClasspath();// SERVLET||REACTIVE; 是servlet还是reactive环境
// BootstrapRegistryInitializer
this.bootstrapRegistryInitializers = new ArrayList(this.getSpringFactoriesInstances(BootstrapRegistryInitializer.class));
// ApplicationContextInitializer
this.setInitializers(this.getSpringFactoriesInstances(ApplicationContextInitializer.class));
// ApplicationListener
this.setListeners(this.getSpringFactoriesInstances(ApplicationListener.class));
this.mainApplicationClass = this.deduceMainApplicationClass();
}注册 BootstrapRegistryInitializer
this.bootstrapRegistryInitializers = new ArrayList(this.getSpringFactoriesInstances(BootstrapRegistryInitializer.class));
//
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) {
ClassLoader classLoader = this.getClassLoader();
// 1、从配置文件读取名称加载
Set<String> names = new LinkedHashSet(SpringFactoriesLoader.loadFactoryNames(type, classLoader));
// 2、获取构造器实例
List<T> instances = this.createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
// 3、排序
AnnotationAwareOrderComparator.sort(instances);
return instances;
}
// 1、加载配置
private static Map<String, List<String>> loadSpringFactories(ClassLoader classLoader) {
Map<String, List<String>> result = (Map)cache.get(classLoader);
if (result != null) {
return result;
} else {
HashMap result = new HashMap();
try {
//核心 从这里知道读取配置文件位置 默认
Enumeration urls = classLoader.getResources("META-INF/spring.factories");
// ... 这里省略迭代器遍历注册
result.replaceAll((factoryType, implementations) -> {
return (List)implementations.stream().distinct().collect(Collectors.collectingAndThen(Collectors.toList(), Collections::unmodifiableList));
});
// 添加到缓存中，下次读取。根据类名读取
cache.put(classLoader, result);
return result;
} catch (IOException var14) {
throw new IllegalArgumentException("Unable to load factories from location [META-INF/spring.factories]", var14);
}
}
}
// 2、获取构造器实例
private <T> List<T> createSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, ClassLoader classLoader, Object[] args, Set<String> names) {
List<T> instances = new ArrayList(names.size());
Iterator var7 = names.iterator();
while(var7.hasNext()) {
String name = (String)var7.next();
try {
// 通过类名反射机制调用，读取Class<T> class
Class<?> instanceClass = ClassUtils.forName(name, classLoader);
Assert.isAssignable(type, instanceClass);
Constructor<?> constructor = instanceClass.getDeclaredConstructor(parameterTypes);
// 获取构造器实例
T instance = BeanUtils.instantiateClass(constructor, args);
// 添加到构造器中
instances.add(instance);
} catch (Throwable var12) {
throw new IllegalArgumentException("Cannot instantiate " + type + " : " + name, var12);
}
}
// 返回
return instances;
}
// 排序 通过debug这里调用的是Integer类型排序方法 List<Integer> list
public static void sort(List<?> list) {
if (list.size() > 1) {
list.sort(INSTANCE);
}
}配置文件
spring-boot:2.7.1.META-INFspring.factorie
org.springframework.context.ApplicationContextInitializer= org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer, org.springframework.boot.context.ContextIdApplicationContextInitializer, org.springframework.boot.context.config.DelegatingApplicationContextInitializer, org.springframework.boot.rsocket.context.RSocketPortInfoApplicationContextInitializer, org.springframework.boot.web.context.ServerPortInfoApplicationContextInitializer
像 BootstrapRegistryInitializer
另外几个配置是从其他配置文件中读取的
例如
注册 ApplicationContextInitializer 、ApplicationListener
同
BootstrapRegistryInitializer加载原理
2、调用run方法
核心
public ConfigurableApplicationContext run(String... args) {
long startTime = System.nanoTime();
DefaultBootstrapContext bootstrapContext = this.createBootstrapContext();
ConfigurableApplicationContext context = null;
this.configureHeadlessProperty();
SpringApplicationRunListeners listeners = this.getRunListeners(args);
listeners.starting(bootstrapContext, this.mainApplicationClass);
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
ConfigurableEnvironment environment = this.prepareEnvironment(listeners, bootstrapContext, applicationArguments);
this.configureIgnoreBeanInfo(environment);
Banner printedBanner = this.printBanner(environment);
context = this.createApplicationContext();
context.setApplicationStartup(this.applicationStartup);
this.prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
// 加载所有注解使用的扫描的组件
this.refreshContext(context);
// 刷新
this.afterRefresh(context, applicationArguments);
Duration timeTakenToStartup = Duration.ofNanos(System.nanoTime() - startTime);
if (this.logStartupInfo) {
(new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), timeTakenToStartup);
}
listeners.started(context, timeTakenToStartup);
this.callRunners(context, applicationArguments);
} catch (Throwable var12) {
this.handleRunFailure(context, var12, listeners);
throw new IllegalStateException(var12);
}
try {
Duration timeTakenToReady = Duration.ofNanos(System.nanoTime() - startTime);
listeners.ready(context, timeTakenToReady);
return context;
} catch (Throwable var11) {
this.handleRunFailure(context, var11, (SpringApplicationRunListeners)null);
throw new IllegalStateException(var11);
}
}所有组件经过
org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader方法加载注册组件
private void registerBeanDefinitionForImportedConfigurationClass(ConfigurationClass configClass) {
AnnotationMetadata metadata = configClass.getMetadata();
AnnotatedGenericBeanDefinition configBeanDef = new AnnotatedGenericBeanDefinition(metadata);
ScopeMetadata scopeMetadata = scopeMetadataResolver.resolveScopeMetadata(configBeanDef);
configBeanDef.setScope(scopeMetadata.getScopeName());
String configBeanName = this.importBeanNameGenerator.generateBeanName(configBeanDef, this.registry);
AnnotationConfigUtils.processCommonDefinitionAnnotations(configBeanDef, metadata);
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(configBeanDef, configBeanName);
definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
// 在这里注册
this.registry.registerBeanDefinition(definitionHolder.getBeanName(), definitionHolder.getBeanDefinition());
configClass.setBeanName(configBeanName);
if (logger.isTraceEnabled()) {
logger.trace("Registered bean definition for imported class '" + configBeanName + "'");
}
}org.springframework.beans.factory.support.DefaultListableBeanFactory
registerBeanDefinition(definitionHolder.getBeanName(), definitionHolder.getBeanDefinition())
@Override
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
Assert.hasText(beanName, "Bean name must not be empty");
Assert.notNull(beanDefinition, "BeanDefinition must not be null");
if (beanDefinition instanceof AbstractBeanDefinition) {
try {
((AbstractBeanDefinition) beanDefinition).validate();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Validation of bean definition failed", ex);
}
}
BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
if (existingDefinition != null) {
if (!isAllowBeanDefinitionOverriding()) {
throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
}
else if (existingDefinition.getRole() < beanDefinition.getRole()) {
// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
if (logger.isInfoEnabled()) {
logger.info("Overriding user-defined bean definition for bean '" + beanName +
"' with a framework-generated bean definition: replacing [" +
existingDefinition + "] with [" + beanDefinition + "]");
}
}
else if (!beanDefinition.equals(existingDefinition)) {
if (logger.isDebugEnabled()) {
logger.debug("Overriding bean definition for bean '" + beanName +
"' with a different definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
else {
if (logger.isTraceEnabled()) {
logger.trace("Overriding bean definition for bean '" + beanName +
"' with an equivalent definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
// 注册
this.beanDefinitionMap.put(beanName, beanDefinition);
}
else {
if (hasBeanCreationStarted()) {
// Cannot modify startup-time collection elements anymore (for stable iteration)
synchronized (this.beanDefinitionMap) {
this.beanDefinitionMap.put(beanName, beanDefinition);
List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
removeManualSingletonName(beanName);
}
}
else {
// Still in startup registration phase
this.beanDefinitionMap.put(beanName, beanDefinition);
this.beanDefinitionNames.add(beanName);
removeManualSingletonName(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (existingDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
else if (isConfigurationFrozen()) {
clearByTypeCache();
}
}