SpringBoot：SpringBoot启动过程
启动几个比较重要的步骤
1.创建上下文实例
2.注册CommandLinePropertySource，吧spring参数都暴露到jvm里面（猜的）
3. 刷新上下文，加载所有到单例的bean
4. 触发CommandLineRunner的beans
spring建议使用一个@Configuration修饰的类来实现bean的配置，除此之外还可以使用xml或者groovy脚本来配置bean。
run的时候可以支持传若干参数，这个是支持了使用jar来启动的时候可以使用参数启动。
代码分析
初始化SpringApplication
/**
* Create a new {@link SpringApplication} instance. The application context will load
* beans from the specified primary sources (see {@link SpringApplication class-level}
* documentation for details. The instance can be customized before calling
* {@link #run(String...)}.
* @param resourceLoader the resource loader to use
* @param primarySources the primary bean sources
* @see #run(Class, String[])
* @see #setSources(Set)
*/
@SuppressWarnings({ "unchecked", "rawtypes" })
public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
this.resourceLoader = resourceLoader;
Assert.notNull(primarySources, "PrimarySources must not be null");
this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
this.webApplicationType = WebApplicationType.deduceFromClasspath();
this.bootstrappers = new ArrayList<>(getSpringFactoriesInstances(Bootstrapper.class));
setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
this.mainApplicationClass = deduceMainApplicationClass();
}
primarySources
通常用来传主类的main方法
WebAppliocationType
存储当前是什么web服务类型，通常是servlet
getSpringFactoriesInstances(Bootstrapper.class) //获取Spring工厂实例
//具体实现如下
private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) {
ClassLoader classLoader = getClassLoader();
// Use names and ensure unique to protect against duplicates
Set<String> names = new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(type, classLoader));
List<T> instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
AnnotationAwareOrderComparator.sort(instances);
return instances;
}
/**
* 这里的代码其实很好理解，就是将meta-inf/spring.factories文件的键值对提取出来
* 看有没有传入class的对应的类，如果就就返回出来这些class
*/
private <T> List<T> createSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes,
ClassLoader classLoader, Object[] args, Set<String> names) {
List<T> instances = new ArrayList<>(names.size());
for (String name : names) {
try {
Class<?> instanceClass = ClassUtils.forName(name, classLoader);
Assert.isAssignable(type, instanceClass);
Constructor<?> constructor = instanceClass.getDeclaredConstructor(parameterTypes);
T instance = (T) BeanUtils.instantiateClass(constructor, args);
instances.add(instance);
}
catch (Throwable ex) {
throw new IllegalArgumentException("Cannot instantiate " + type + " : " + name, ex);
}
}
return instances;
}
/**
* 通过以上在String.factories里面获取出来的Class对象来反射创建类。
*/
@SuppressWarnings("unchecked")
private <T> List<T> createSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes,
ClassLoader classLoader, Object[] args, Set<String> names) {
List<T> instances = new ArrayList<>(names.size());
for (String name : names) {
try {
Class<?> instanceClass = ClassUtils.forName(name, classLoader);
Assert.isAssignable(type, instanceClass);
Constructor<?> constructor = instanceClass.getDeclaredConstructor(parameterTypes);
T instance = (T) BeanUtils.instantiateClass(constructor, args);
instances.add(instance);
}
catch (Throwable ex) {
throw new IllegalArgumentException("Cannot instantiate " + type + " : " + name, ex);
}
}
return instances;
}
bootstrappers
开始感觉这个字段的用处不是很明白，看了使用的地方之后：
/**
* Callback interface that can be used to initialize a {@link BootstrapRegistry} before it
* is used.
* 这个是一个回的接口传入的是一个启动注册器。
* @author Phillip Webb
* @since 2.4.0
* @see SpringApplication#addBootstrapper(Bootstrapper)
* @see BootstrapRegistry
*/
public interface Bootstrapper {
/**
* Initialize the given {@link BootstrapRegistry} with any required registrations.
* @param registry the registry to initialize
*/
void intitialize(BootstrapRegistry registry);
}
/**
* 启动注册器里面提供了如下的方法，也就是如果我门在自己的starter里面写了一个BootStraper的依赖
* 那么我们可以在BootStrapper里面去将我门要做到事情通过这个BootStrappRegistry的注册方法来注册即可。
* 一个简单的例子，我门如果要实现启动器的回掉钩子看，那么我门就可以通过这个BootStraopper来调用BootStrapRegistry
* 的addCloseListener来实现我门想要的功能
*/
public interface BootstrapRegistry {
/**
* Register a specific type with the registry. If the specified type has already been
* registered and has not been obtained as a {@link Scope#SINGLETON singleton}, it
* will be replaced.
* @param <T> the instance type
* @param type the instance type
* @param instanceSupplier the instance supplier
*/
<T> void register(Class<T> type, InstanceSupplier<T> instanceSupplier);
/**
* Register a specific type with the registry if one is not already present.
* @param <T> the instance type
* @param type the instance type
* @param instanceSupplier the instance supplier
*/
<T> void registerIfAbsent(Class<T> type, InstanceSupplier<T> instanceSupplier);
/**
* Return if a registration exists for the given type.
* @param <T> the instance type
* @param type the instance type
* @return {@code true} if the type has already been registered
*/
<T> boolean isRegistered(Class<T> type);
/**
* Return any existing {@link InstanceSupplier} for the given type.
* @param <T> the instance type
* @param type the instance type
* @return the registered {@link InstanceSupplier} or {@code null}
*/
<T> InstanceSupplier<T> getRegisteredInstanceSupplier(Class<T> type);
/**
* Add an {@link ApplicationListener} that will be called with a
* {@link BootstrapContextClosedEvent} when the {@link BootstrapContext} is closed and
* the {@link ApplicationContext} has been prepared.
* @param listener the listener to add
*/
void addCloseListener(ApplicationListener<BootstrapContextClosedEvent> listener);
/**
* Supplier used to provide the actual instance when needed.
*
* @param <T> the instance type
* @see Scope
*/
@FunctionalInterface
interface InstanceSupplier<T> {
/**
* Factory method used to create the instance when needed.
* @param context the {@link BootstrapContext} which may be used to obtain other
* bootstrap instances.
* @return the instance
*/
T get(BootstrapContext context);
/**
* Return the scope of the supplied instance.
* @return the scope
* @since 2.4.2
*/
default Scope getScope() {
return Scope.SINGLETON;
}
/**
* Return a new {@link InstanceSupplier} with an updated {@link Scope}.
* @param scope the new scope
* @return a new {@link InstanceSupplier} instance with the new scope
* @since 2.4.2
*/
default InstanceSupplier<T> withScope(Scope scope) {
Assert.notNull(scope, "Scope must not be null");
InstanceSupplier<T> parent = this;
return new InstanceSupplier<T>() {
@Override
public T get(BootstrapContext context) {
return parent.get(context);
}
@Override
public Scope getScope() {
return scope;
}
};
}
/**
* Factory method that can be used to create a {@link InstanceSupplier} for a
* given instance.
* @param <T> the instance type
* @param instance the instance
* @return a new {@link InstanceSupplier}
*/
static <T> InstanceSupplier<T> of(T instance) {
return (registry) -> instance;
}
/**
* Factory method that can be used to create a {@link InstanceSupplier} from a
* {@link Supplier}.
* @param <T> the instance type
* @param supplier the supplier that will provide the instance
* @return a new {@link InstanceSupplier}
*/
static <T> InstanceSupplier<T> from(Supplier<T> supplier) {
return (registry) -> (supplier != null) ? supplier.get() : null;
}
}
/**
* The scope of a instance.
* @since 2.4.2
*/
enum Scope {
/**
* A singleton instance. The {@link InstanceSupplier} will be called only once and
* the same instance will be returned each time.
*/
SINGLETON,
/**
* A prototype instance. The {@link InstanceSupplier} will be called whenver an
* instance is needed.
*/
PROTOTYPE
}
}
setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
设置初始化器，这个初始化器可以在refresh之前被调用
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
this.mainApplicationClass = deduceMainApplicationClass();
设置引用监听器和主类方法。
启动过程
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch(); //启动和结束时间的监听器
stopWatch.start();//开始
//根据之前创建的BootStrapper来创建bootStrap的上下文
DefaultBootstrapContext bootstrapContext = createBootstrapContext();
ConfigurableApplicationContext context = null; // init
configureHeadlessProperty(); // setHeadLess，也可以使用此类的headLess来设置java.awt.headless
SpringApplicationRunListeners listeners = getRunListeners(args); //获取应用运行时监听器
listeners.starting(bootstrapContext, this.mainApplicationClass);// 触发开始事件
try {
//解析封装命令行参数，这个应该就是SpringApplication类注释上面的CommandLineSource
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
//准备环境，见详细分析准备环境
ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
//配置环境中忽略的bean
configureIgnoreBeanInfo(environment);
//输出banner，这个是可以自定义的
Banner printedBanner = printBanner(environment);
// 简单new一下ApplicationContext
context = createApplicationContext();
//设置 startup，这个是用来记录步骤消耗时间的
context.setApplicationStartup(this.applicationStartup);
//准备上下文详细分析2
prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
//刷新上下文详细分析3
refreshContext(context);
afterRefresh(context, applicationArguments);
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
}
listeners.started(context);
//执行两个runner CommandLineruner和ApplicationRunner
callRunners(context, applicationArguments);
}
catch (Throwable ex) {
handleRunFailure(context, ex, listeners);
throw new IllegalStateException(ex);
}
try {
//已经启动了事件
listeners.running(context);
}
catch (Throwable ex) {
handleRunFailure(context, ex, null);
throw new IllegalStateException(ex);
}
return context;
}
准备环境的分析
private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,
DefaultBootstrapContext bootstrapContext, ApplicationArguments applicationArguments) {
// Create and configure the environment
//创建环境
ConfigurableEnvironment environment = getOrCreateEnvironment();
//根据命令行变量来配置环境，其中有转换服务，配置ComandLinePropertyResouce
configureEnvironment(environment, applicationArguments.getSourceArgs());
// 处理命令行参数--代码1
ConfigurationPropertySources.attach(environment);
//触发环境已经准备好了事件
listeners.environmentPrepared(bootstrapContext, environment);
//默认参数移动到最后
DefaultPropertiesPropertySource.moveToEnd(environment);
//配置profiles，不过这里为什么可以多个profile
configureAdditionalProfiles(environment);
//将环境和applicationContext绑定在一起，这个应该是一个互相赋值的过程
bindToSpringApplication(environment);
//如果设置过环境了，就直接转换下环境就行
if (!this.isCustomEnvironment) {
environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,
deduceEnvironmentClass());
}
//可配置的属性再次放在第一
ConfigurationPropertySources.attach(environment);
return environment;
}
//根据容器类型类创建不同的环境
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();
}
}
protected void configureEnvironment(ConfigurableEnvironment environment, String[] args) {
if (this.addConversionService) {
ConversionService conversionService = ApplicationConversionService.getSharedInstance();
environment.setConversionService((ConfigurableConversionService) conversionService);
}
configurePropertySources(environment, args);
configureProfiles(environment, args);
}
//代码1
public static void attach(Environment environment) {
Assert.isInstanceOf(ConfigurableEnvironment.class, environment);
MutablePropertySources sources = ((ConfigurableEnvironment) environment).getPropertySources();
PropertySource<?> attached = sources.get(ATTACHED_PROPERTY_SOURCE_NAME);
if (attached != null && attached.getSource() != sources) {
sources.remove(ATTACHED_PROPERTY_SOURCE_NAME);
attached = null;
}
if (attached == null) {
//主要是这里，我猜测是将命令行属性直接全部梭哈到sources里面，然后后面通过resolver进行处理
sources.addFirst(new ConfigurationPropertySourcesPropertySource(ATTACHED_PROPERTY_SOURCE_NAME,
new SpringConfigurationPropertySources(sources)));
}
}
准备上下文详细分析2
private void prepareContext(DefaultBootstrapContext bootstrapContext, ConfigurableApplicationContext context,
ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments, Banner printedBanner) {
//将上下文里面设置上环境
context.setEnvironment(environment);
//设置转换服务
postProcessApplicationContext(context);
//调用初始化上下文的回调
applyInitializers(context);
//上下文准备好了
listeners.contextPrepared(context);
//BootStrap是负责启动的上下文，这个标志这BootStrap过程已经搞完了，接下来是ApplicationContext要搞的事情了
bootstrapContext.close(context);
if (this.logStartupInfo) {
logStartupInfo(context.getParent() == null);
logStartupProfileInfo(context);
}
// Add boot specific singleton beans
ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
if (printedBanner != null) {
beanFactory.registerSingleton("springBootBanner", printedBanner);
}
if (beanFactory instanceof DefaultListableBeanFactory) {
((DefaultListableBeanFactory) beanFactory)
.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
}
if (this.lazyInitialization) {
//设置了懒加载那么就要设置懒加载的执行器
context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
}
// Load the sources
Set<Object> sources = getAllSources();
Assert.notEmpty(sources, "Sources must not be empty");
//执行资源加载，类，bean资源
load(context, sources.toArray(new Object[0]));
//加载事件
listeners.contextLoaded(context);
}
刷新上下文 详细分析3
调用过程：SpringApplication#refreshContext => ConfigurableApplicationContext#refresh
//刷新过程代码
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {//同步
//记录一个事件
StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");
//准备刷新主要是一些属性的设置
// Prepare this context for refreshing.
prepareRefresh();
// 获取beanfactory
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// 准备BeanFactory，设置依赖，环境里面的自带的bean
prepareBeanFactory(beanFactory);
try {
//准备BeanFactoryProcess
postProcessBeanFactory(beanFactory);
//事件
StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
// 调用BeanFactoryProcess
invokeBeanFactoryPostProcessors(beanFactory);
// 注册下BeanPostProcessor， 这个接口里面有postProcessBeforeInitialization 和postProcessAfterInitialization， 在bean初始化的时候被调用
registerBeanPostProcessors(beanFactory);
//postProcess事件结束了，这个过程结束了
beanPostProcess.end();
// 初始化messageSource，国际化，不配置就会有个默认的
initMessageSource();
//初始化事件分发器 -- 可以分发事件，添加事件的监听等处理
initApplicationEventMulticaster();
//由子类实现的方法，做一些特殊的处理，例如ServletWebServerApplicationContext要创建webserver
onRefresh();
// 将监听器注册到分发器上
registerListeners();
//初始化所有的单例bean，执行bean的那些创建bean的接口，详细分析3 bean的创建过程
finishBeanFactoryInitialization(beanFactory);
// 结束刷新过程，发出刷新结束的事件
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
contextRefresh.end();
}
}
}
protected void prepareRefresh() {
// Switch to active.
//开始事件
this.startupDate = System.currentTimeMillis();
//激活
this.closed.set(false);
this.active.set(true);
if (logger.isDebugEnabled()) {
if (logger.isTraceEnabled()) {
logger.trace("Refreshing " + this);
}
else {
logger.debug("Refreshing " + getDisplayName());
}
}
// 初始化属性
initPropertySources();
// Validate that all properties marked as required are resolvable:
// see ConfigurablePropertyResolver#setRequiredProperties
//验证属性
getEnvironment().validateRequiredProperties();
//保留下监听器 ，close的时候使用
if (this.earlyApplicationListeners == null) {
this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);
}
else {
// Reset local application listeners to pre-refresh state.
this.applicationListeners.clear();
this.applicationListeners.addAll(this.earlyApplicationListeners);
}
// Allow for the collection of early ApplicationEvents,
// to be published once the multicaster is available...
this.earlyApplicationEvents = new LinkedHashSet<>();
}
//PostProcessorRegistrationDelegate 处理postProcessBeanFactory方法 -- BeanFactoryPostProcessor
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
//这里的整体逻辑都是调用相关的postProcessBeanFactory方法
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<>();
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
registryProcessor.postProcessBeanDefinitionRegistry(registry);
registryProcessors.add(registryProcessor);
}
else {
regularPostProcessors.add(postProcessor);
}
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
// Separate between BeanDefinitionRegistryPostProcessors that implement
// PriorityOrdered, Ordered, and the rest.
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
boolean reiterate = true;
while (reiterate) {
reiterate = false;
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
reiterate = true;
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
}
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
}
else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, invoke all other BeanFactoryPostProcessors.
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
for (String postProcessorName : nonOrderedPostProcessorNames) {
nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
beanFactory.clearMetadataCache();
}
bean的创建过程
调用过程：
finishBeanFactoryInitialization => beanFactory.preInstantiateSingletons(); => AbstractBeanFactory#doGetBean
protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
String beanName = transformedBeanName(name);
Object beanInstance;
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);
if (sharedInstance != null && args == null) {
if (logger.isTraceEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.trace("Returning eagerly cached instance of singleton bean '" + beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
}
else {
logger.trace("Returning cached instance of singleton bean '" + beanName + "'");
}
}
beanInstance = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// BeanPostProcessors 的beforeInit和afterInit调用的地方，
BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
String nameToLookup = originalBeanName(name);
if (parentBeanFactory instanceof AbstractBeanFactory) {
return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
nameToLookup, requiredType, args, typeCheckOnly);
}
else if (args != null) {
// Delegation to parent with explicit args.
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else if (requiredType != null) {
// No args -> delegate to standard getBean method.
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
else {
return (T) parentBeanFactory.getBean(nameToLookup);
}
}
if (!typeCheckOnly) {
markBeanAsCreated(beanName);
}
//主要看这里，创建过程
StartupStep beanCreation = this.applicationStartup.start("spring.beans.instantiate")
.tag("beanName", name);
try {
if (requiredType != null) {
beanCreation.tag("beanType", requiredType::toString);
}
RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);
//先处理依赖的bean，这个
// Guarantee initialization of beans that the current bean depends on.
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
for (String dep : dependsOn) {
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
registerDependentBean(dep, beanName);
try {
getBean(dep);
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
// Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
// 执行创建过程
return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
// Explicitly remove instance from singleton cache: It might have been put there
// eagerly by the creation process, to allow for circular reference resolution.
// Also remove any beans that received a temporary reference to the bean.
destroySingleton(beanName);
throw ex;
}
});
beanInstance = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
beanInstance = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
String scopeName = mbd.getScope();
if (!StringUtils.hasLength(scopeName)) {
throw new IllegalStateException("No scope name defined for bean ´" + beanName + "'");
}
Scope scope = this.scopes.get(scopeName);
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
Object scopedInstance = scope.get(beanName, () -> {
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
});
beanInstance = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
}
catch (IllegalStateException ex) {
throw new ScopeNotActiveException(beanName, scopeName, ex);
}
}
}
catch (BeansException ex) {
beanCreation.tag("exception", ex.getClass().toString());
beanCreation.tag("message", String.valueOf(ex.getMessage()));
cleanupAfterBeanCreationFailure(beanName);
throw ex;
}
finally {
beanCreation.end();
}
}
return adaptBeanInstance(name, beanInstance, requiredType);
}
//创建bean的过程，这里
protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
if (logger.isTraceEnabled()) {
logger.trace("Creating instance of bean '" + beanName + "'");
}
RootBeanDefinition mbdToUse = mbd;
// Make sure bean class is actually resolved at this point, and
// clone the bean definition in case of a dynamically resolved Class
// which cannot be stored in the shared merged bean definition.
Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
mbdToUse = new RootBeanDefinition(mbd);
mbdToUse.setBeanClass(resolvedClass);
}
// Prepare method overrides.
try {
mbdToUse.prepareMethodOverrides();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
beanName, "Validation of method overrides failed", ex);
}
try {
// BeanPostProcessors 调用beforeInit和AfterInit方法，如果又返回值那么就用那个直接当作bean，如果没有就
//继续往下走，这个是给外部使用来接管创建bean过程的代码
Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
if (bean != null) {
return bean;
}
}
catch (Throwable ex) {
throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,
"BeanPostProcessor before instantiation of bean failed", ex);
}
try {
//如果上面的postProcessor没有创建出来bean的话就直接执行创建过程
Object beanInstance = doCreateBean(beanName, mbdToUse, args);
if (logger.isTraceEnabled()) {
logger.trace("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
}
catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) {
// A previously detected exception with proper bean creation context already,
// or illegal singleton state to be communicated up to DefaultSingletonBeanRegistry.
throw ex;
}
catch (Throwable ex) {
throw new BeanCreationException(
mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", ex);
}
}
//执行官创建bean，
protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
// Instantiate the bean.
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
Object bean = instanceWrapper.getWrappedInstance();
Class<?> beanType = instanceWrapper.getWrappedClass();
if (beanType != NullBean.class) {
mbd.resolvedTargetType = beanType;
}
// Allow post-processors to modify the merged bean definition.
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
//BeanPostProcessor postProcessMergedBeanDefinition
applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Post-processing of merged bean definition failed", ex);
}
mbd.postProcessed = true;
}
}
// Eagerly cache singletons to be able to resolve circular references
// even when triggered by lifecycle interfaces like BeanFactoryAware.
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
isSingletonCurrentlyInCreation(beanName));
if (earlySingletonExposure) {
if (logger.isTraceEnabled()) {
logger.trace("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
}
// Initialize the bean instance.
Object exposedObject = bean;
try {
//设置bean的属性值，属性值存储在instanceWrapper里面
populateBean(beanName, mbd, instanceWrapper);
//执行初始化过程
exposedObject = initializeBean(beanName, exposedObject, mbd);
}
catch (Throwable ex) {
if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
throw (BeanCreationException) ex;
}
else {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
}
}
if (earlySingletonExposure) {
Object earlySingletonReference = getSingleton(beanName, false);
if (earlySingletonReference != null) {
if (exposedObject == bean) {
exposedObject = earlySingletonReference;
}
else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
String[] dependentBeans = getDependentBeans(beanName);
Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length);
for (String dependentBean : dependentBeans) {
if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
actualDependentBeans.add(dependentBean);
}
}
if (!actualDependentBeans.isEmpty()) {
throw new BeanCurrentlyInCreationException(beanName,
"Bean with name '" + beanName + "' has been injected into other beans [" +
StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
"] in its raw version as part of a circular reference, but has eventually been " +
"wrapped. This means that said other beans do not use the final version of the " +
"bean. This is often the result of over-eager type matching - consider using " +
"'getBeanNamesForType' with the 'allowEagerInit' flag turned off, for example.");
}
}
}
}
// Register bean as disposable.
try {
//把实现disposableBean的注册。
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
return exposedObject;
}
//执行初始化过程
protected Object initializeBean(String beanName, Object bean, @Nullable RootBeanDefinition mbd) {
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
invokeAwareMethods(beanName, bean);
return null;
}, getAccessControlContext());
}
else {
// 调用aware方法 BeanNameAware BeanClassLoaderAware BeanFactoryAware
invokeAwareMethods(beanName, bean);
}
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
//beforeInit
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
//InitializingBean#afterPropertiesSet
invokeInitMethods(beanName, wrappedBean, mbd);
}
catch (Throwable ex) {
throw new BeanCreationException(
(mbd != null ? mbd.getResourceDescription() : null),
beanName, "Invocation of init method failed", ex);
}
if (mbd == null || !mbd.isSynthetic()) {
//BeanAfterInits s s s s s s s s s
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
}
关于BeanPostProcessor
//这个是在初始化的时候使用的，
public interface BeanPostProcessor {
//初始化之前，
default Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
return bean;
}
//初始化之后
default Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
return bean;
}
}
//但是他有个子类是接管实例话的
public interface InstantiationAwareBeanPostProcessor extends BeanPostProcessor {
//接管初始化过程
@Nullable
default Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
return null;
}
default boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
return true;
}
@Nullable
default PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName)
throws BeansException {
return null;
}
@Deprecated
@Nullable
default PropertyValues postProcessPropertyValues(
PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeansException {
return pvs;
}
}
BeanWrapper和Bean之间的关系，Bean是由BeanWrapper创建的。
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