首先閱讀源碼是件很痛苦的事情。第一步整合源碼更痛苦,
參考:https://blog.csdn.net/qq_40088250/article/details/104219666
人家確實寫的不錯,可以拿來避避坑!!!
整合完成之後,新建項目進行測試。
一,Spring啓動的兩種方式
1.1 基於註解:
import com.learn.day1.AppConfig;
import com.learn.day1.AppService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.stereotype.Component;
//@Configuration
@Component
public class Day2Test {
/**
* 查看Spring是如何注入的
* @param args
*/
public static void main(String[] args) {
AnnotationConfigApplicationContext
context = new AnnotationConfigApplicationContext(Day2Test.class);
System.out.println(context.getBean(AppService.class));
}
@Bean
public AppService getService(){
return new AppService();
}
}
1.2 基於xml文件:
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("application-day1.xml");
System.out.println(context.getBean(AppService.class));
}
Springcontext.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.2.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.2.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-4.2.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-4.2.xsd ">
<!-- 掃描組件 -->
<context:component-scan base-package="com.learn"/>
<!-- 支持spring註解 -->
<context:annotation-config/>
</beans>
這裏以註解方式爲主:看懂後就要開始SpringBoot源碼學習
二:AnnotationConfigApplicationContext:Spring上下文
由下圖可知:
acx是一個讀取器:ResourseLoader
acx是一個Bean工廠:BeanFacctory
acx是一個BD註冊器:AliasRegistry
.....
* 獨立的Spring上下文
* 可以接收@Configuration 註解的類
* 或者@Compontent 註解的類
在實例化時創建了兩個對象
private final AnnotatedBeanDefinitionReader reader;BD讀取器
private final ClassPathBeanDefinitionScanner scanner;BD掃描器
當創建AnnotationConfigApplicationContext的執行流程
public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) {
this();
register(annotatedClasses);
refresh();
}
第一步:調用this()方法:
執行 GenericApplicationContext 構造方法創建Bean工廠
public GenericApplicationContext() {
this.beanFactory = new DefaultListableBeanFactory();
}
執行 AbstractApplicationContext構造方法創建解析器
public AbstractApplicationContext() {
this.resourcePatternResolver = getResourcePatternResolver();
}
執行 DefaultResourceLoader構造方法創建CalssLoader
public DefaultResourceLoader() {
this.classLoader = ClassUtils.getDefaultClassLoader();
}
第二步:初始化 AnnotatedBeanDefinitionReader
實例化對象 BeanDefinitionRegistry 其實就是AnnotationConfigApplicationContext
實例化對象 BeanNameGenerator 名稱生成器
實例化對象 ScopeMetadataResolver 生成方式解析器
public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry, Environment environment) {
Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
Assert.notNull(environment, "Environment must not be null");
//當前的註冊器就是指的是AnnotationConfigApplicationContext
this.registry = registry;
this.conditionEvaluator = new ConditionEvaluator(registry, environment, null);
AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
}
第三步:初始化 ClassPathBeanDefinitionScanner 與第二個對象基本類似,只不過職能不同
實例化對象 BeanDefinitionRegistry 其實就是AnnotationConfigApplicationContext
實例化對象 BeanNameGenerator 名稱生成器
實例化對象 ScopeMetadataResolver 生成方式解析器
第四步:調用
register(annotatedClasses)方法
最終調用AnnotatedBeanDefinitionReader 的doRegisterBean方法用來生成AnnotatedGenericBeanDefinition
<T> void doRegisterBean(Class<T> annotatedClass, @Nullable Supplier<T> instanceSupplier, @Nullable String name,
@Nullable Class<? extends Annotation>[] qualifiers, BeanDefinitionCustomizer... definitionCustomizers) {
AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(annotatedClass);
if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) {
return;
}
abd.setInstanceSupplier(instanceSupplier);
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);
abd.setScope(scopeMetadata.getScopeName());
String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry));
AnnotationConfigUtils.processCommonDefinitionAnnotations(abd);
if (qualifiers != null) {
for (Class<? extends Annotation> qualifier : qualifiers) {
if (Primary.class == qualifier) {
abd.setPrimary(true);
}
else if (Lazy.class == qualifier) {
abd.setLazyInit(true);
}
else {
abd.addQualifier(new AutowireCandidateQualifier(qualifier));
}
}
}
for (BeanDefinitionCustomizer customizer : definitionCustomizers) {
customizer.customize(abd);
}
//相當於一個map 通過name 獲取BD
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName);
definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);
}
結果生成BeanDefinitionHolder key:name value:BeanDefinition。方便通過getKey獲取
第五步:調用
registerBeanDefinition方法 將BD加入到容器中
最終調用 DefaultListableBeanFactory 對象的registerBeanDefinition方法,將BD加入到BeanFactory中的map中去
截止到這裏項目中需要的BD已註冊到BeanFactory中
@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 + "]");
}
}
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);
}
}
第五步:調用
refresh()方法刷新容器
三:Spring 核心 refresh()方法
// 容器刷新前的準備,設置上下文狀態,獲取屬性,驗證必要的屬性等
prepareRefresh();
// 獲取新的beanFactory,銷燬原有beanFactory、爲每個bean生成BeanDefinition等
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// 配置標準的beanFactory,設置ClassLoader,設置SpEL表達式解析器,
// 添加忽略注入的接口,添加bean,添加bean後置處理器等
prepareBeanFactory(beanFactory);
try {
// 模板方法,此時,所有的beanDefinition已經加載,但是還沒有實例化。
//允許在子類中對beanFactory進行擴展處理。比如添加ware相關接口自動裝配設置,添加後置處理器等,
postProcessBeanFactory(beanFactory);
//實例化並調用所有註冊的beanFactory後置處理器
// (實現接口BeanFactoryPostProcessor的bean,在beanFactory標準初始化之後執行)。
invokeBeanFactoryPostProcessors(beanFactory);
// 實例化和註冊beanFactory中擴展了BeanPostProcessor的bean。
registerBeanPostProcessors(beanFactory);
// 初始化國際化工具類MessageSource
initMessageSource();
// 初始化事件廣播器
initApplicationEventMulticaster();
// 模板方法,在容器刷新的時候可以自定義邏輯,不同的Spring容器做不同的事情
onRefresh();
// 註冊監聽器,廣播early application events
registerListeners();
// 實例化剩餘的Bean。
finishBeanFactoryInitialization(beanFactory);
// 初始化上下文的生命週期處理器
finishRefresh();
}
5.1 prepareRefresh()用來設置基本信息比如環境時間啓動標識等
5.2 obtainFreshBeanFactory()獲取BeanFactory,設置刷新狀態等 。
5.3 prepareBeanFactory()方法 關聯BeanFactory當前的是上下文 classLoader設置BeanPostProcessor等。
5.4 postProcessBeanFactory()方法 允許在子類中對beanFactory進行擴展處理。比如添加後置處理器等。
5.5 invokeBeanFactoryPostProcessors()方法 實例化所有Bean並調用所有註冊的beanFactory後置處理器
5.6 registerBeanPostProcessors ()方法 實例化BeanPostProcessor
5.7 initMessageSource() 國際化設置
5.8 initApplicationEventMulticaster() 初始化ApplicationContext 監聽
5.9 onRefresh()
5.10 registerListeners() 註冊監聽器
5.11 finishBeanFactoryInitialization () 實例化剩餘的Bean
5.12 finishRefresh()初始化生命週期,刪除緩存等