
目前我們分析的代碼已經到了容器處理相關的SpringBoot原理,代碼如下:
public ConfigurableApplicationContext run(String... args) {
//DONE 擴展點 SpringApplicationRunListeners listeners.starting();
//DONE 組態檔的處理和抽象封裝 ConfigurableEnvironment
//容器相關處理
//1)核心就是創建了Context和BeanFactory物件,內部初始化了Reader和Scanner,加載了一些內部Bean
context = createApplicationContext();
exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
new Class[] {ConfigurableApplicationContext.class }, context);
//2) 給容器Context、BeanFactory設定了一堆屬性和組件,執行了initialize/listener的擴展點
//比較重要屬性有:singletonObjects 、beanDefinitionMap 、beanFactoryPostProcessors、applicationListeners
prepareContext(context, environment, listeners, applicationArguments,printedBanner);
//3) TODO 容器關鍵的擴展操作執行了,也是很多容器功能和第三方功能的擴展之處
refreshContext(context);
//其他邏輯
}
已經分析的階段如下圖:

prepareContext()準備完成之后,接下來就是refreshContext(),容器關鍵的擴展操作執行了,也是很多容器功能和第三方功能的擴展之處,我們來一起看下吧,
快速摸一下refreshCotenxt的脈絡
refreshCotenxt()方法最終呼叫了容器的refresh方法,我們還是先來看下它的脈絡,之后從中間抽絲剝繭的找到重點,
先來快速的看下它的代碼脈絡:
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
initMessageSource();
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
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();
}
}
}
整體由一個try-catch構成,內部有很多個方法組成,看上去讓人找不到重點所在,感覺每個方法都挺重要的,
我第一次看的時候,每個方法,都分開從脈絡到細節,分析,
最后抓大放小,其實refresh在上面最重要的三個方法是:
invokeBeanFactoryPostProcessors 執行了容器擴展點,自動裝配配置、其他技術的常擴展處
onRefresh 內嵌的web容器啟動,默認是tomcat
finishBeanFactoryInitialization bean的實體化

那么,本著抓大放小的思想,其余的方法不是很重要,這個確認程序就不帶大家一一去展開看每個方法了,
當然除了核心給大家分析上面這三個方法,其他的會順帶提到下,讓大家了解下就行,
今天我們就來先refresh的看看第一個核心方法做了什么,
invokeBeanFactoryPostProcessors執行容器擴展點之前的主要操作
refresh()執行到invokeBeanFactoryPostProcessors是非常重要的邏輯,前面的方法大體可以概括如下圖所示:

整個程序中,不是很重要,用淺藍色標注的內容:
涉及設定了一些無關緊要的值,startupDate、setSerializationId、BeanExpressionResolver等等
也設涉及了基本物件集合的初始化earlyApplicationEvents、earlyApplicationListeners
也標注了幾個容器注入物件需要特別考慮和忽略的介面等
setignoreDependencyInterface 設定忽略的介面,不會注冊成bean
registerResolvableDependency 指明Spring內部一些介面 默認會注入的容器物件
相對重要一點的點是,圖中用綠色標注了下:
主要還補充了一些Spring自己的對Bean的擴展點BeanPostProcessor,Spring默認的BeanPostProcessor,補充一些BeanDefinition、registerSingleton補充一些內部的物件到集合,
術語普及BeanPostProcessor是什么?
之前BeanFactoryPostProcessor是對容器的擴展,主要有一個方法,可以給容器設定屬性,補充一些單例物件,補充一些BeanDefinition,
那BeanPostProcessor是對bean的擴展,有before和after兩類方法,對Bean如何做擴展,在bean的創建前后,給bean補充一些屬性等,
invokeBeanFactoryPostProcessors之前的邏輯,我們快速過一下就好,當中并沒有特別重要的邏輯,主要是Spring對內部的處理,給容器補充了一堆屬性,
invokeBeanFactoryPostProcessors的核心脈絡
大體了解了invokeBeanFactoryPostProcessors之前的主要操作后,接下來我們核心首先來先看看這個方法的脈絡,看看它主要做了寫什么的?
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
// Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
// (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
乍一看,這個方法好像挺簡單的, 只有2段邏輯,你很容易抓到重點
invokeBeanFactoryPostProcessors執行擴展點,這個應該是核心觸發容器的擴展點地方,
根據條件,補充一個Bean的擴展操作,BeanPostProcessor,這個明顯不是啥重點邏輯,之前做過很多類似的操作了,
如下圖所示:

那你深入到PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors這個方法是,你會發現如下一大坨的代碼:
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// 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);
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);
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);
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();
}
這個方法,初看上去的是有一點復雜,但是沒關系,你可以先摸清一下它的脈絡:
1)首先主要有一個if-else組成
2)之后是連續的3個for回圈
如下圖:

好了,這就是這個方法的核心脈絡了,接下來我們分別來弄清楚,if-else邏輯在做什么,之后的3個for回圈在做什么,這個方法基本就知道在做什么了,
讓我們來看下第一個if-else在做什么呢?
if-esle核心脈絡邏輯
第一個if-esle核心邏輯主要是判斷了容器是否實作了BeanDefinitionRegistry這個介面,從而決定如何執行BeanFactoryPostProcessor的擴展操作,
BeanDefinitionRegistry這個介面,之前我們普及過,封裝了對BeanDefinition常見操作的介面,容器默認實作了這個介面,所以一般它也代表了容器,可以通過實作的方法,維護容器內List
,
代碼如下:
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
if (beanFactory instanceof BeanDefinitionRegistry) {
}else {
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
}
容器默認是實作了BeanDefinitionRegistry介面,正常會執行if邏輯,由于if邏輯相對復雜,我們先來看下,else邏輯在做什么,再去理解if邏輯,
else邏輯
else邏輯比較簡單主要就是觸發了入參中的beanFactoryPostProcessors的擴展方法postProcessBeanFactory(),代碼如下:
private static void invokeBeanFactoryPostProcessors(
Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) {
for (BeanFactoryPostProcessor postProcessor : postProcessors) {
postProcessor.postProcessBeanFactory(beanFactory);
}
}
疑問:入參中這些內部的BeanFactoryPostProcessor這個是哪里來的?
是通過從容器中的一個屬性 List
這個屬性時之前通過listener等擴展點增加進來的一些Spring內部的BeanFactoryPostProcessor,主要有如下三個:
beanFactoryPostProcessors = {ArrayList@2882} size = 3
0 = {SharedMetadataReaderFactoryContextInitializer
$CachingMetadataReaderFactoryPostProcessor@2887}
1 = {ConfigurationWarningsApplicationContextInitializer
$ConfigurationWarningsPostProcessor@2888}
2 = {ConfigFileApplicationListener
$PropertySourceOrderingPostProcessor@2889}
我們這里把它們稱之為inernalBeanFactoryPostProcessors
如下圖:

那最終else邏輯其實主要就是觸發了這些內部BeanFactoryPostProcessor的postProcessBeanFactory()擴展方法而已,整體如下圖所示:

至于這些擴展操作具體做了什么,我們稍后在分析,先整體摸清楚方法脈絡在來看細節,
if邏輯
了解了else 的邏輯之后,我們再看下if主要做了什么,因為if-else邏輯,其實默認是不會執行的else的,優先執行的肯定是if,
這里要先普及一些概念,才可以更好的理解if的代碼邏輯,
術語普及BeanDefinitionRegistryPostProcessor是什么?
BeanDefinitionRegistryPostProcessor
也是擴展點,繼承自BeanFactoryPostProcessor,對BeanFactoryPostProcessor增加了一個擴展方法而已,
整體設計如下圖所示:

BeanFactoryPostProcessor可以有兩個擴展操作
也就是說,原來的BeanFactoryPostProcessor的擴展方法,從一個增加到了兩個,一個是postProcessBeanFactory(),另一個事postProcessBeanDefinitionRegistry(),
另外一個要強調的其實是BeanFactoryPostProcessor來源有兩個
1)容器中,事先通過擴展點加入的BeanFactoryPostProcessor
2)BeanDefinition中的,定義的但是沒有實體化的BeanFactoryPostProcessor
如下圖:

BeanFactoryPostProcessor可以有兩個擴展操作、BeanFactoryPostProcessor來源有兩個
這2點很關鍵,帶著這個知識,我們再看if邏輯,就會很容易,
if邏輯主要代碼如下:
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);
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);
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);
currentRegistryProcessors.clear();
}
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
這個if邏輯的代碼脈絡,主要的邏輯是有3個for+1while邏輯,其實可以按照擴展操作1和擴展操作2的執行劃分開,
讓我們分別看下,
執行擴展方法1:postProcessBeanDefinitionRegistry()
執行擴展方法1時,首先就需要分別從兩個來源開始執行,而且執行的是實作了BeanDefinitionRegistryPostProcessor的BeanFactoryPostProcessor,
主要邏輯可以概括如下圖:

用文字解釋下上圖的話,就是:
1)容器中,之前增加的內部相關的BeanFactoryPostProcessor有沒有實作這個BeanDefinitionRegistryPostProcessor介面增加了擴展方法postProcessBeanDefinitionRegistry()的?如果有,對應的所有BeanFactoryPostProcessor,通過for回圈執行這個方法,并且記錄這些執行的BeanFactoryPostProcessor和未執行的BeanFactoryPostProcessor,
2)容器中,之前增加的內部相關的BeanDefinition中,有沒有定義為BeanFactoryPostProcessor的,如果有,按照實作了PrioriyOrder介面、Order介面、無Order介面的分別執行擴展方法postProcessBeanDefinitionRegistry(),使用了2for回圈+一個while回圈執行,執行完成記錄這些BeanFactoryPostProcessor,
執行擴展方法2:postProcessBeanFactory()
之前執行擴展方法1的時候記錄的所有BeanFactoryPostProcessor,包括擴展點之前添加的,BeanDefinition定義的,
我們可以通過記錄的這些BeanFactoryPostProcessor ,來在執行執行擴展方法2—postProcessBeanFactory(),
如下圖所示:

整個if-else的邏輯的脈絡,我們就摸清楚了,至于這些擴展操作具體做了什么,我們稍后在分析,還是先整體摸清楚方法脈絡在來看細節,
3個For回圈的核心脈絡邏輯
invokeBeanFactoryPostProcessors的核心脈絡中,除了一個if-else邏輯,接下來的就是連續的3次for回圈執行,
分為主要排序、排序、無順序要求的BeanFactoryPostProcessor三類,主要執行擴展點BeanFactoryPostProcessor的postProcessBeanFactory方法,
這個邏輯聽上去,其實和之前if-else中的邏輯是很像的,只不過之前執行的是BeanDefinitionRegistryPostProcessor,
而且此時的BeanFactoryPostProcessor都來自與BeanDefinition中的,
你可能說,之前已經執行過了BeanDefinition中的BeanFactoryPostProcessor了,怎么還有?
之前執行的是Spring內部定義好的一些BeanFactoryPostProcessor,在執行了if-else邏輯后,其實掃描出來了ClassPath下更多第三方和其他的BeanFactoryPostProcessor
這些新掃描出來BeanFactoryPostProcessor,參考之前BeanDefinitionRegistryPostProcessor的執行方式,執行了如下的擴展操作:

3個for的邏輯的脈絡,其實并不復雜,至于這些擴展操作具體做了什么,既然我們摸清楚了整個方法invokeBeanFactoryPostProcessors的脈絡了,我們下一節馬上就來分析,
小結
最后,簡單小結下,invokeBeanFactoryPostProcessors主要做的就是執行BeanDefinitionRegistryPostProcessor、BeanFactoryPostProcessor的2個擴展方法,這些BeanFactoryPostProcessors可能是內部Spring實作添加好的,也可能是來自ClassPath掃描出來的BeanFactoryPostProcessors,
這些擴展點具體執行了寫什么,有哪些重點操作呢?我們下一節一起來仔細看看細節,我們下節再見!
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