1 简介

  springIOC它是对bean进行管理。

  我们通常可以通过xml、properties、yml、注解等来配置bean的信息

  spring读取这些配置信息,解析,生成BeanDefinition(用来存储Bean的定义信息)

  根据beanDefinition来创建对象,设置属性....,最后把对象放入容器(BeanFactory)中,但我们需要使用bean时,从容器中那就可以了。

 

2 bean

  在spring中,可以把bean分为两大类,普通对象和容器对象

3 BeanFactory和FactoryBean

  它们两个都是用来创建对象的

  当使用BeanFactory的时候,必须遵循完整的过程,这个过程是由spring管理控制的

  当使用FactoryBean的时候,只需要调用getObject就可以返回对象,整个对象的创建过程是由用户自己定义的,更加灵活,它在getObject中自己去创建对象

package org.springframework.beans.factory;

import org.springframework.lang.Nullable;

public interface FactoryBean<T> {

    String OBJECT_TYPE_ATTRIBUTE = "factoryBeanObjectType";

    @Nullable
T getObject() throws Exception; @Nullable
Class<?> getObjectType(); default boolean isSingleton() {
return true;
} }

4 BeanDefinition

  从配置中读取到bean的配置信息,通过BeanDefinitionReader解析,生成的存储bean定义信息的实例

5 spring的bean默认是单例

  scope属性用来配置创建bean采用什么模式。

  spring创建对象时是采用反射创建的,且默认采用的是单例。

  spring Bean可以设置一个属性,叫做scope,可以设置四种变量。最常用的是前两种。singleton(单例-默认的)、prototype(每次获取都创建新的)

6 aware方法

  它是用来获取当前对象的容器对象

  比如说我们要获取到bean的AplicationContext对象

  演示获取ApplicationContext容器对象

public class BeanTest implements ApplicationContextAware {

    private Integer id;

    private String name;

    private ApplicationContext applicationContext;

    private BeanFactory beanFactory;

    public Integer getId() {
return id;
} public void setId(Integer id) {
this.id = id;
} public String getName() {
return name;
} public void setName(String name) {
this.name = name;
} public ApplicationContext getApplicationContext() {
return applicationContext;
} public void setApplicationContext(ApplicationContext applicationContext) {
this.applicationContext = applicationContext;
} public BeanFactory getBeanFactory() {
return beanFactory;
} public void setBeanFactory(BeanFactory beanFactory) {
this.beanFactory = beanFactory;
}
}
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.3.xsd"> <bean id="beantest" class="com.spring.test1.BeanTest">
<property name="name" value="张三"></property>
<property name="id" value="111"></property>
</bean> </beans>
public class Test1 {

    public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("Test.xml");
BeanTest bean = context.getBean(BeanTest.class);
System.out.println(bean.getName());
System.out.println(bean.getApplicationContext());
} }

执行结果:

张三
org.springframework.context.support.ClassPathXmlApplicationContext@7e6cbb7a, started on Sun Mar 13 16:11:15 CST 2022

我们获得了ApplicationContext对象。

ApplicationContextAware 源码

public interface ApplicationContextAware extends Aware {
void setApplicationContext(ApplicationContext applicationContext) throws BeansException;
}

执行aware方法,也就是执行setApplicationContext方法,会把容器对象ApplicationContext赋值给我们定义的applicationContext属性。

7 postProcesser

在实例化的过程中,怎么对beanfactory和bean的信息进行修改呢?

可以使用 BeanFactoryPostProcesser和BeanPostProcesser

演示

package com.spring.test1;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware; public class BeanTest implements ApplicationContextAware { private Integer id; private String name; private ApplicationContext applicationContext; private BeanFactory beanFactory; public Integer getId() {
return id;
} public void setId(Integer id) {
this.id = id;
} public String getName() {
return name;
} public void setName(String name) {
this.name = name;
} public ApplicationContext getApplicationContext() {
return applicationContext;
} public void setApplicationContext(ApplicationContext applicationContext) {
this.applicationContext = applicationContext;
} public BeanFactory getBeanFactory() {
return beanFactory;
} public void setBeanFactory(BeanFactory beanFactory) {
this.beanFactory = beanFactory;
}
}
package com.spring.test1;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.stereotype.Component; public class MyBeanFactoryPostProcesser implements BeanFactoryPostProcessor {
public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
System.out.println("自定义的BeanFactoryPostProcessor执行");
}
}
package com.spring.test1;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor; import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.lang.Nullable;
import org.springframework.stereotype.Component; public class MyBeanPostProcesser implements BeanPostProcessor { public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
System.out.println("自定义的BeanPostProcessor的before");
return bean;
} public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
System.out.println("自定义的BeanPostProcessor的after");
return bean;
}
}
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.3.xsd"> <bean id="beantest" class="com.spring.test1.BeanTest">
<property name="name" value="张三"></property>
<property name="id" value="111"></property>
</bean> <bean id="myBeanFactoryPostProcesser" class="com.spring.test1.MyBeanFactoryPostProcesser"> </bean> <bean id="myBeanPostProcesser" class="com.spring.test1.MyBeanPostProcesser"> </bean> </beans>
package com.spring.test1;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext; public class Test1 { public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("Test.xml");
BeanTest bean = context.getBean(BeanTest.class);
System.out.println(bean.getName());
System.out.println(bean.getApplicationContext());
} }
自定义的BeanFactoryPostProcessor执行
自定义的BeanPostProcessor的before
自定义的BeanPostProcessor的after
张三
org.springframework.context.support.ClassPathXmlApplicationContext@7e6cbb7a, started on Sun Mar 13 16:28:59 CST 2022 Process finished with exit code 0

8 init-method

示例

其它代码不变,在BeanTest定义一个方法

package com.spring.test1;

import com.sun.org.apache.xml.internal.security.Init;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware; public class BeanTest implements ApplicationContextAware { private Integer id; private String name; private ApplicationContext applicationContext; private BeanFactory beanFactory; public Integer getId() {
return id;
} public void setId(Integer id) {
this.id = id;
} public String getName() {
return name;
} public void setName(String name) {
this.name = name;
} public ApplicationContext getApplicationContext() {
return applicationContext;
} public void setApplicationContext(ApplicationContext applicationContext) {
this.applicationContext = applicationContext;
} public BeanFactory getBeanFactory() {
return beanFactory;
} public void setBeanFactory(BeanFactory beanFactory) { this.beanFactory = beanFactory;
} public void init(){
System.out.println("init-method执行");
} }

在配置文件中加上init-method属性

<bean id="beantest" class="com.spring.test1.BeanTest" init-method="init">
<property name="name" value="张三"></property>
<property name="id" value="111"></property>
</bean>

执行结果,看到init-method方法是在BeanPostProcessor的before和after之间执行的

自定义的BeanFactoryPostProcessor执行
自定义的BeanPostProcessor的before
init-method执行
自定义的BeanPostProcessor的after
张三

8 springIOC的bean的创建主要过程

  1 创建beanFactory容器

  2 加载配置文件,解析bean定义的信息,包装成BeanDefinition

  3 执行BeanFactoryPostProcesser

  4 准备工作,准备BeanPostProcessor,广播器,监听器

  5 实例化操作

  6 初始化操作

  7 获取对象

9 下面通过debug来看整个过程,测试准备

9.1 实体类

public class BeanTest implements ApplicationContextAware {

    private Integer id;

    private String name;

    private ApplicationContext applicationContext;

    private BeanFactory beanFactory;

    public Integer getId() {
return id;
} public void setId(Integer id) {
this.id = id;
} public String getName() {
return name;
} public void setName(String name) {
this.name = name;
} public ApplicationContext getApplicationContext() {
return applicationContext;
} public void setApplicationContext(ApplicationContext applicationContext) {
this.applicationContext = applicationContext;
} public BeanFactory getBeanFactory() {
return beanFactory;
} public void setBeanFactory(BeanFactory beanFactory) {
this.beanFactory = beanFactory;
}
}

9.2 配置属性

Test.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.3.xsd"> <bean id="beantest" class="com.ruoyi.weixin.user.Test.BeanTest">
<property name="name" value="张三"></property>
<property name="id" value="111"></property>
</bean> </beans>

9.3 测试类

public class SpringBeanInitTest {

    public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("Test.xml");
BeanTest bean = context.getBean(BeanTest.class);
System.out.println(bean.getName());
System.out.println(bean.getApplicationContext());
} }

下面是debug的过程

9.4 进入ClassPathXmlApplicationContext类,构造函数

public ClassPathXmlApplicationContext(
String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
throws BeansException {
      //调用父类构造函数
super(parent);
      //设置BeanDefinition的配置信息路径
setConfigLocations(configLocations);
if (refresh) {
      //容器初始化
refresh();
}
}

9.5 进入refresh()方法

    @Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
//前戏,做日容器刷新前的准备工作
        //1.设置容器的启动时间
        //2.设置活跃状态为true
        //3.设置关闭状态为false
        //4.获取Envirenment对象,并加载当前系统属性值到Envirenment
        //5.准备监听器和事件的集合对象,默认为空的集合
prepareRefresh(); //创建容器对象ConfigurableListableBeanFactory
        //加载xml配置文件到当前容器对象中,最重要是就是BeanDefinition
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // Prepare the bean factory for use in this context.
       //BeanFactory准备工作,对各种属性进行填充
prepareBeanFactory(beanFactory); try {
// Allows post-processing of the bean factory in context subclasses.
          //这是一个空方法,子类可以覆盖这个方法,在这个方法做额外的处理。此处我们自己一般不做额外的处理工作
postProcessBeanFactory(beanFactory); // Invoke factory processors registered as beans in the context.
          //调用各种BeanFactory增强器
invokeBeanFactoryPostProcessors(beanFactory); // Register bean processors that intercept bean creation.
          //注册bean处理器,这里只有注册功能,真正调用是getBean方法
registerBeanPostProcessors(beanFactory); // Initialize message source for this context.
          //为上下文初始化message资源,即不同语言的消息体,国际化处理,简单来说就是为了支持不同语言(如中文、英文不同语言的展示)
initMessageSource(); // Initialize event multicaster for this context.
          //初始化事件监听多路广播器
initApplicationEventMulticaster(); // Initialize other special beans in specific context subclasses.
          //留给子类来初始化其它的bean
onRefresh(); // Check for listener beans and register them.
          //在所有注册的bean中查找监听器bean,注册到消息广播中,也就是注册监听器
registerListeners(); // Instantiate all remaining (non-lazy-init) singletons.
          //初始化剩下的单实例(非懒加载的)
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();
}
}
}

9.6 第一个方法prepareRefresh

//前戏,做日容器刷新前的准备工作(不用太在意)
//1.设置容器的启动时间
//2.设置活跃状态为true
//3.设置关闭状态为false
//4.获取Envirenment对象,并加载当前系统属性值到Envirenment
//5.准备监听器和事件的集合对象,默认为空的集合
protected void prepareRefresh() {
// 设置容器启动时间.
this.startupDate = System.currentTimeMillis();
    //容器的关闭标志位
this.closed.set(false);
    //容器活跃状态
this.active.set(true);
    //记录日志
if (logger.isDebugEnabled()) {
if (logger.isTraceEnabled()) {
logger.trace("Refreshing " + this);
}
else {
logger.debug("Refreshing " + getDisplayName());
}
} //空的方法,留给子类实现,用来初始化属性资源(可以不管它)
initPropertySources(); //创建并获取环境对象,验证需要的属性文件是否已放入环境对象中
getEnvironment().validateRequiredProperties(); // 判断刷新前的应用程序的监听器集合是否为空,如果为空,将监听器添加到集合中
if (this.earlyApplicationListeners == null) {
this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);
}
else {
// 如果不为空,清空集合
this.applicationListeners.clear();
this.applicationListeners.addAll(this.earlyApplicationListeners);
} // Allow for the collection of early ApplicationEvents,
// to be published once the multicaster is available...
     //创建刷新前监听事件集合
this.earlyApplicationEvents = new LinkedHashSet<>();
}

9.7 第二个方法obtainFreshBeanFactory(这里就完成了第一步BeanFactory对象的创建)

1)创建容器对象ConfigurableListableBeanFactory
2)加载xml配置文件到当前容器对象中,最重要是就是BeanDefinition
往里面进入到方法refreshBeanFactory()
    protected final void refreshBeanFactory() throws BeansException {
    //如果存在BeanFactory,则销毁
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
      //创建DefaultListableBeanFactory对象
DefaultListableBeanFactory beanFactory = createBeanFactory();
      //为了序列化设置id,可以从id反序列化到BeanFactory对象
beanFactory.setSerializationId(getId());
      //定制BeanFactory,设置相关属性,包括是否允许覆盖同名称的不同定义的对象以及循环依赖
customizeBeanFactory(beanFactory);
      //初始化docunmentReader,并进行xml文件读取和解析,默认命名空间的解析,自定义标签的解析
loadBeanDefinitions(beanFactory);
this.beanFactory = beanFactory;
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}

我们debug到loadBeanDefinitions(beanFactory)这里,此时查看beanFactory的两个属性,beanDefinitionMap和beanDefinitionMapNames,发现都是空的

执行完loadBeanDefinitions(beanFactory)之后,再查看,发现大小变为1了

打开beanDefinitionMap属性查看,发现名字为beantest的BeanDefinition,类型为BeanTest,正式我们在xml中定义的bean对象的信息

beanclass往下找到propertyValues属性,可以看到name和id两个属性的值

 这里就完成了第二步,BeanDefinition已经加载完成了

9.8 第三个方法prepareBeanFactory(beanFactory)

  这个方法先不深究,就是对当前beanFactory的一些属性来填充值

9.9 第四个方法postProcessBeanFactory

这是一个空方法,子类可以覆盖这个方法,在这个方法做额外的处理。此处我们自己一般不做额外的处理工作
不用管这个方法

protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
}

9.10 第五个方法invokeBeanFactoryPostProcessors(beanFactory);调用各种BeanFactory增强器

  这里面爱怎么执行怎么执行,不去看了,太多了

9.11 第六个方法 registerBeanPostProcessors(beanFactory)

  注册bean处理器。注意这里只有注册功能,把BeanPostProcessors准备好,真正调用是getBean方法

9.12 第七个方法 initMessageSource()

  为上下文初始化message资源,即不同语言的消息体,国际化处理,简单来说就是为了支持国际化(如中文、英文不同语言的展示)

  就好像这个网站,右侧有english和pyccknn(俄语)两种选项,可以转换语言 。它就是为了支持这个东西

9.13 第八个方法initApplicationEventMulticaster()

  初始化事件监听多路广播器。

  广播事件给监听器用。

  这里也就是观察者模式。

9.14 第九个方法onRefresh()

  这是一个空方法,子类可以覆盖这个方法,在这个方法做额外的处理,来初始化其它的bean

    protected void onRefresh() throws BeansException {
// For subclasses: do nothing by default.
}

9.15 第十个方法registerListeners()

注册监听器。在所有注册的bean中查找监听器bean,注册到消息广播中

9.16 第十一个方法finishBeanFactoryInitialization(beanFactory)

初始化剩下的单实例(非懒加载的)
更详细的创建过程:https://www.cnblogs.com/jthr/p/15919598.html
    protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// Initialize conversion service for this context.
if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
beanFactory.setConversionService(
beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
} // Register a default embedded value resolver if no bean post-processor
// (such as a PropertyPlaceholderConfigurer bean) registered any before:
// at this point, primarily for resolution in annotation attribute values.
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
} // Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
} // Stop using the temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(null); // Allow for caching all bean definition metadata, not expecting further changes.
beanFactory.freezeConfiguration(); // Instantiate all remaining (non-lazy-init) singletons.
      //实例化剩下的非懒加载单利对象
beanFactory.preInstantiateSingletons();
}

方法前面做了一些列的set、add操作,还是在为BeanFactory做属性赋值,也就是还在做准备工作

到beanFactory.preInstantiateSingletons()方法:实例化剩下的非懒加载单利对象

进入preInstantiateSingletons()方法

    @Override
public void preInstantiateSingletons() throws BeansException {
if (logger.isTraceEnabled()) {
logger.trace("Pre-instantiating singletons in " + this);
} // Iterate over a copy to allow for init methods which in turn register new bean definitions.
// While this may not be part of the regular factory bootstrap, it does otherwise work fine.
     //创建一个集合,将所有的BeanDefinition的名字放入集合
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames); // Trigger initialization of all non-lazy singleton beans...
    //触发所有非懒加载的单利bean的实例化,遍历集合的对象
for (String beanName : beanNames) {
        //合并父类BeanDefinition
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
        //条件判断 非抽象、单利、非懒加载
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
          //判断是否实现了FactoryBean接口
if (isFactoryBean(beanName)) {
            //根据&+beanName来获取具体的对象
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
              //进行类型转换
if (bean instanceof FactoryBean) {
FactoryBean<?> factory = (FactoryBean<?>) bean;
              //判断这个Factory是否需要立即初始化
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged(
(PrivilegedAction<Boolean>) ((SmartFactoryBean<?>) factory)::isEagerInit,
getAccessControlContext());
}
else {
isEagerInit = (factory instanceof SmartFactoryBean &&
((SmartFactoryBean<?>) factory).isEagerInit());
}
if (isEagerInit) {
getBean(beanName);
}
}
}
else {
getBean(beanName);
}
}
} // Trigger post-initialization callback for all applicable beans...
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}

这里,前面做了一些列的判断,做到了getBean方法,进入getBean方法

@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);
}

再进入doGetBean方法。注意,在spring中,以do开头的方法,是实际上干活的方法

    protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException { String beanName = transformedBeanName(name);
Object bean; // 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 + "'");
}
}
bean = 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);
} // Check if bean definition exists in this factory.
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);
} try {
RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args); // 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 {
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;
}
});
bean = 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);
}
bean = 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);
}
});
bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
}
catch (IllegalStateException ex) {
throw new BeanCreationException(beanName,
"Scope '" + scopeName + "' is not active for the current thread; consider " +
"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
ex);
}
}
}
catch (BeansException ex) {
cleanupAfterBeanCreationFailure(beanName);
throw ex;
}
} // Check if required type matches the type of the actual bean instance.
if (requiredType != null && !requiredType.isInstance(bean)) {
try {
T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);
if (convertedBean == null) {
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
return convertedBean;
}
catch (TypeMismatchException ex) {
if (logger.isTraceEnabled()) {
logger.trace("Failed to convert bean '" + name + "' to required type '" +
ClassUtils.getQualifiedName(requiredType) + "'", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
return (T) bean;
}

这个方法进行一系列的处理之后,会调用方法createBean(beanName, mbd, args);

进入createBean方法

    @Override
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 {
// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
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 {
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);
}
}
再进行了一些列的处理,调用doCreateBean(beanName, mbdToUse, args)方法,这个方法就是实际创建bean的方法
进入doCreateBean方法
    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 {
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 {
populateBean(beanName, mbd, instanceWrapper);
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 {
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
} return exposedObject;
}

里面又调用了方法 createBeanInstance(beanName, mbd, args);它是根据执行bean使用对应的策略创建新的实例。如工厂方法、构造方法、简单初始化

进入createBeanInstance方法

protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) {
// Make sure bean class is actually resolved at this point.
      //确定需要创建的bean的实例的类可以实例化
Class<?> beanClass = resolveBeanClass(mbd, beanName); if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
}
    //判断当前Definition是否包含实例供应器。此处相当于一个回调方法,利用回调方法来创建bean
Supplier<?> instanceSupplier = mbd.getInstanceSupplier();
if (instanceSupplier != null) {
return obtainFromSupplier(instanceSupplier, beanName);
}
    //如果工厂方法不为空,使用工厂方法策略来初始化策略
if (mbd.getFactoryMethodName() != null) {
return instantiateUsingFactoryMethod(beanName, mbd, args);
} // Shortcut when re-creating the same bean...
boolean resolved = false;
boolean autowireNecessary = false;
if (args == null) {
synchronized (mbd.constructorArgumentLock) {
if (mbd.resolvedConstructorOrFactoryMethod != null) {
resolved = true;
autowireNecessary = mbd.constructorArgumentsResolved;
}
}
}
if (resolved) {
if (autowireNecessary) {
return autowireConstructor(beanName, mbd, null, null);
}
else {
return instantiateBean(beanName, mbd);
}
} // Candidate constructors for autowiring?
    //获取构造方法
Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
if (ctors != null || mbd.getResolvedAutowireMode() == AUTOWIRE_CONSTRUCTOR ||
mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) {
return autowireConstructor(beanName, mbd, ctors, args);
} // Preferred constructors for default construction?
ctors = mbd.getPreferredConstructors();
if (ctors != null) {
return autowireConstructor(beanName, mbd, ctors, null);
} // No special handling: simply use no-arg constructor.
return instantiateBean(beanName, mbd);
}
前面做了一系列的处理,获取了class对象,获取构造器,最后调用instantiateBean(beanName, mbd)方法
进入instantiateBean方法
protected BeanWrapper instantiateBean(String beanName, RootBeanDefinition mbd) {
try {
Object beanInstance;
if (System.getSecurityManager() != null) {
beanInstance = AccessController.doPrivileged(
(PrivilegedAction<Object>) () -> getInstantiationStrategy().instantiate(mbd, beanName, this),
getAccessControlContext());
}
else {
          //获取实例化策略并进行实例化操作
beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, this);
}
BeanWrapper bw = new BeanWrapperImpl(beanInstance);
initBeanWrapper(bw);
return bw;
}
catch (Throwable ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);
}
}

里面调用beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, this);

进入instantiate方法

@Override
public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) {
// Don't override the class with CGLIB if no overrides.
if (!bd.hasMethodOverrides()) {
Constructor<?> constructorToUse;
synchronized (bd.constructorArgumentLock) {
constructorToUse = (Constructor<?>) bd.resolvedConstructorOrFactoryMethod;
if (constructorToUse == null) {
final Class<?> clazz = bd.getBeanClass();
if (clazz.isInterface()) {
throw new BeanInstantiationException(clazz, "Specified class is an interface");
}
try {
if (System.getSecurityManager() != null) {
constructorToUse = AccessController.doPrivileged(
(PrivilegedExceptionAction<Constructor<?>>) clazz::getDeclaredConstructor);
}
else {
              //获取无参构造器
constructorToUse = clazz.getDeclaredConstructor();
}
bd.resolvedConstructorOrFactoryMethod = constructorToUse;
}
catch (Throwable ex) {
throw new BeanInstantiationException(clazz, "No default constructor found", ex);
}
}
}
return BeanUtils.instantiateClass(constructorToUse);
}
else {
// Must generate CGLIB subclass.
return instantiateWithMethodInjection(bd, beanName, owner);
}
}

里面又获取了无参构造,后面调用了BeanUtils.instantiateClass(constructorToUse);

进入instantiateClass方法

public static <T> T instantiateClass(Constructor<T> ctor, Object... args) throws BeanInstantiationException {
Assert.notNull(ctor, "Constructor must not be null");
try {
ReflectionUtils.makeAccessible(ctor);
if (KotlinDetector.isKotlinReflectPresent() && KotlinDetector.isKotlinType(ctor.getDeclaringClass())) {
return KotlinDelegate.instantiateClass(ctor, args);
}
else {
Class<?>[] parameterTypes = ctor.getParameterTypes();
Assert.isTrue(args.length <= parameterTypes.length, "Can't specify more arguments than constructor parameters");
Object[] argsWithDefaultValues = new Object[args.length];
for (int i = 0 ; i < args.length; i++) {
if (args[i] == null) {
Class<?> parameterType = parameterTypes[i];
argsWithDefaultValues[i] = (parameterType.isPrimitive() ? DEFAULT_TYPE_VALUES.get(parameterType) : null);
}
else {
argsWithDefaultValues[i] = args[i];
}
}
return ctor.newInstance(argsWithDefaultValues);
}
}
catch (InstantiationException ex) {
throw new BeanInstantiationException(ctor, "Is it an abstract class?", ex);
}
catch (IllegalAccessException ex) {
throw new BeanInstantiationException(ctor, "Is the constructor accessible?", ex);
}
catch (IllegalArgumentException ex) {
throw new BeanInstantiationException(ctor, "Illegal arguments for constructor", ex);
}
catch (InvocationTargetException ex) {
throw new BeanInstantiationException(ctor, "Constructor threw exception", ex.getTargetException());
}
}

看到里面调用了return ctor.newInstance(argsWithDefaultValues);通过构造器创建了实例。这么深,终于看到了创建实例操作

回到doCreateBean方法,执行完了createBeanInstance,往下看

populateBean(beanName, mbd, instanceWrapper);

接下来执行了populateBean方法,这个方法是给bean的属性赋值的。

在这里执行后,id和name就有值了。application和beanFactory两个属性还没有值

接下来又执行了方法exposedObject = initializeBean(beanName, exposedObject, mbd);方法

进入initializeBean

    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 {
invokeAwareMethods(beanName, bean);
} Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
} try {
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()) {
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
} return wrappedBean;
}

里面执行了invokeAwareMethods(beanName, bean);

也就是执行aware方法。

该方法执行完成后,beanFactory赋值了,而applicationContext属性还没有值

我们进入invokeAwareMethods方法,发现它只调用了setBeanName,setBeanClassLoader,setBeanFactory,所以只会给beanName,beanClassLoader、beanFactory赋值

private void invokeAwareMethods(String beanName, Object bean) {
if (bean instanceof Aware) {
if (bean instanceof BeanNameAware) {
((BeanNameAware) bean).setBeanName(beanName);
}
if (bean instanceof BeanClassLoaderAware) {
ClassLoader bcl = getBeanClassLoader();
if (bcl != null) {
((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
}
}
if (bean instanceof BeanFactoryAware) {
((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
}
}
}

invokeAwareMethods执行完成,我们继续看initializeBean方法,接下来执行了applyBeanPostProcessorsBeforeInitialization方法

wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);

执行了BeanPostProcessors里面的before,

这个方法会为applicationContext属性赋值

在下面又会执行invokeInitMethods(beanName, wrappedBean, mbd);方法

这里会执行bean的init方法

再下一步执行applyBeanPostProcessorsAfterInitialization

wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);

执行了BeanPostProcessors里面的after

这样子,就有了创建bean的完整脉络。

 

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