- Spring Framework简单介绍
Core Container模块:Core 和 Beans 模块是框架的基础部分,提供 IoC (控制反转)和 DI(依赖注入)特性。 Context构建于Core 和 Bean 之上,提供了一个BeanFactory来访问应用组件,添加了国际化(例如资源绑定)、事件传播、资源加载等。SpEL提供了强大的表达式语言。
Data Access/Integration模块:JDBC提供了一个JDBC抽象层,ORM对象关系映射如:JPA,XOM提供了一个ObjectXML映射关系,JMS提供了生产消息和消费消息的功能,Transactions:提供了编程和声明性的事务管理,这些事务类必须实现特定的接口。
Web模块:提供了面向Web的特性,比如Spring Mvc,使用servlet listeners初始化IoC容器以及一个面向Web的应用上下文,典型的父子容器关系。
Aop模块:Aspects模块提供了对AspectJ集成的支持。Instrumentation模块提供了class instrumentation支持和classloader实现,动态字节码插桩。
Test模块:Test模块支持使用Junit等对Spring组件进行测试
- Ioc的核心思想以及常用注解和应用
Ioc的核心思想:资源组件不由使用方管理,而由不使用资源的第三方管理,这可以带来很多好处。第一,资源集中管理,实现资源的可配置和易管理。第二,降低了使用资源双方的依赖程度,也就是我们说的耦合度
常用的注解:
@Configuration 相对于配置文件中的<beans>
@Bean 相对于配置文件中的<bean>
@CompentScan 包扫描
@Scope 配置Bean的作用域
@Lazy 是否开启懒加载
@Conditional 条件注解 spring boot中经常用到
@Import 导入组件
......
应用:
package com.toby.ioc.iocprinciple;
import org.springframework.beans.factory.annotation.Autowired;
public class PrincipleAspect {
@Autowired
private PrincipleLog principleLog;
/*public PrincipleLog getPrincipleLog() {
return principleLog;
}
public void setPrincipleLog(PrincipleLog principleLog) {
this.principleLog = principleLog;
}*/
}
package com.toby.ioc.iocprinciple;
public class PrincipleBean {
}
package com.toby.ioc.iocprinciple;
import org.springframework.beans.factory.annotation.Autowire;
import org.springframework.context.annotation.*;
@Configuration
@ComponentScan(basePackages = {"com.toby.ioc.iocprinciple"})
//@ImportResource("classpath:Beans.xml")
@Import(PrincipleService.class)
public class PrincipleConfig {
@Bean
public PrincipleBean principleBean(){
return new PrincipleBean();
}
//@Bean(autowire = Autowire.BY_TYPE)
@Bean
public PrincipleAspect principleAspect(){
return new PrincipleAspect();
}
@Bean
@Primary
public PrincipleLog principleLog(){
return new PrincipleLog();
}
@Bean
public PrincipleLog principleLog2(){
return new PrincipleLog();
}
}
package com.toby.ioc.iocprinciple;
import org.springframework.stereotype.Controller;
@Controller
public class PrincipleController {
}
package com.toby.ioc.iocprinciple;
import org.springframework.stereotype.Repository;
@Repository
public class PrincipleDao {
}
package com.toby.ioc.iocprinciple;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
/**
* @desc: 循环依赖
* @author: toby
*/
@Component
public class PrincipleInstanceA {
@Autowired
private PrincipleInstanceB instanceB;
}
package com.toby.ioc.iocprinciple;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
/**
* @desc: 循环依赖
* @author: toby
*/
@Component
public class PrincipleInstanceB {
@Autowired
private PrincipleInstanceA instanceA;
}
package com.toby.ioc.iocprinciple;
/**
* @desc:
* @author: toby
*/
public class PrincipleLog {
}
package com.toby.ioc.iocprinciple;
/**
* @desc:
* @author: toby
*/
public class PrincipleService {
}
package com.toby.ioc.iocprinciple;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
/**
* @desc: ioc原理解析 启动
* @author: toby
*/
public class PrincipleMain {
public static void main(String[] args) {
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(PrincipleConfig.class);
/*for (String beanDefinitionName : context.getBeanDefinitionNames()) {
System.out.println("bean定义名称:" + beanDefinitionName);
}*/
PrincipleAspect principleAspect = context.getBean(PrincipleAspect.class);
context.close();
System.out.println(principleAspect);
}
}
完整的代码请见:spring
- getBean的源码解析
beanfactory的类继承图:
首先创建org.springframework.context.annotation.AnnotationConfigApplicationContext#AnnotationConfigApplicationContext(java.lang.Class<?>…)
public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) {
//主要的作用往容器中注册系统级别的处理器,为处理我们自定义的配置类准备,以及初始化classpath下的bean定义扫描
this();
//注册我们自定义的配置类
register(annotatedClasses);
//Ioc容器刷新12大步
refresh();
}
org.springframework.context.support.AbstractApplicationContext#refresh 12大步
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
//1:准备刷新上下文环境
prepareRefresh();
//2:获取初始化Bean工厂
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
//3:对bean工厂进行填充属性
prepareBeanFactory(beanFactory);
try {
//4:Spring开放接口 留给子类去实现该接口
postProcessBeanFactory(beanFactory);
//:5:调用我们的bean工厂的后置处理器
invokeBeanFactoryPostProcessors(beanFactory);
// 6:注册我们bean后置处理器
registerBeanPostProcessors(beanFactory);
// 7:初始化国际化资源处理器
initMessageSource();
//8:初始化事件多播器
initApplicationEventMulticaster();
//9:// 这个方法同样也是留个子类实现的springboot也是从这个方法进行启动tomcat的.
onRefresh();
//10:把我们的事件监听器注册到多播器上
registerListeners();
//11:实例化所有的非懒加载的单实例bean
finishBeanFactoryInitialization(beanFactory);
//12:最后刷新容器 发布刷新事件(Spring cloud eureka也是从这里启动的)
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();
}
}
}
第11步:实例化所有的非懒加载的单实例bean
org.springframework.context.support.AbstractApplicationContext#finishBeanFactoryInitialization
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(new StringValueResolver() {
@Override
public String resolveStringValue(String strVal) {
return 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);
//冻结所有的bean定义
beanFactory.freezeConfiguration();
//实例化剩余的非懒加载的单实例bean
beanFactory.preInstantiateSingletons();
}
实例化剩余的非懒加载的单实例bean:
@Override
public void preInstantiateSingletons() throws BeansException {
if (logger.isDebugEnabled()) {
logger.debug("Pre-instantiating singletons in " + this);
}
// 获取容器中所有beanName
List<String> beanNames = new ArrayList<String>(this.beanDefinitionNames);
//触发实例化所有的非懒加载的单实例bean
for (String beanName : beanNames) {
//合并bean定义
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
//非抽象,单实例,非懒加载
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
//是否工厂bean,是要获取factorybean的getObject方法
if (isFactoryBean(beanName)) {
//factorybean的bean那么前面加了一个FACTORY_BEAN_PREFIX就是&
final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
@Override
public Boolean run() {
return ((SmartFactoryBean<?>) factory).isEagerInit();
}
}, getAccessControlContext());
}
else {
isEagerInit = (factory instanceof SmartFactoryBean &&
((SmartFactoryBean<?>) factory).isEagerInit());
}
if (isEagerInit) {
//调用getBean流程
getBean(beanName);
}
}
else {//非工厂bean
//调用getBean流程
getBean(beanName);
}
}
}
//触发初始化之后的回调,到这里所有的bean都存放在了单例缓冲池中了
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged(new PrivilegedAction<Object>() {
@Override
public Object run() {
smartSingleton.afterSingletonsInstantiated();
return null;
}
}, getAccessControlContext());
}
else {
//触发实例化之后的方法afterSingletonsInstantiated
smartSingleton.afterSingletonsInstantiated();
}
}
}
}
getBean流程
org.springframework.beans.factory.support.AbstractBeanFactory#getBean(java.lang.String)
public Object getBean(String name) throws BeansException {
//获取bean
return doGetBean(name, null, null, false);
}
org.springframework.beans.factory.support.AbstractBeanFactory#doGetBean
protected <T> T doGetBean(
final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
throws BeansException {
//转化bean名称
final String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
//先从单例缓冲池中获取,第一次肯定没有,后面都有
Object sharedInstance = getSingleton(beanName);
if (sharedInstance != null && args == null) {
if (logger.isDebugEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
}
else {
logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
}
}
//为什么不直接返回,原因就是可能是FactoryBean
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
//如果是多实例,不能解决循环依赖,抛出异常
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
//获取父容器
BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
String nameToLookup = originalBeanName(name);
if (args != null) {
// Delegation to parent with explicit args.
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else {
// No args -> delegate to standard getBean method.
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
}
if (!typeCheckOnly) {
markBeanAsCreated(beanName);
}
try {
//合并bean定义
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
//检查当前创建的bean定义是不是抽象
checkMergedBeanDefinition(mbd, beanName, args);
//处理依赖bean,获取依赖bean名称
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 + "'");
}
//保存的是依赖和beanName之间的映射关系
registerDependentBean(dep, beanName);
try {
//获取依赖的bean
getBean(dep);
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
//创建单例bean
if (mbd.isSingleton()) {
//把beanName 和一个singletonFactory匿名内部类传入用于回调
sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
try {
//创建bean
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();
final 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, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
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 && bean != null && !requiredType.isInstance(bean)) {
try {
return getTypeConverter().convertIfNecessary(bean, requiredType);
}
catch (TypeMismatchException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Failed to convert bean '" + name + "' to required type '" +
ClassUtils.getQualifiedName(requiredType) + "'", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
return (T) bean;
}
createBean:
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#createBean(java.lang.String, org.springframework.beans.factory.support.RootBeanDefinition, java.lang.Object[])
protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
if (logger.isDebugEnabled()) {
logger.debug("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);
}
//干活的do方法,真正的创建我们的bean的实例对象的过程
Object beanInstance = doCreateBean(beanName, mbdToUse, args);
if (logger.isDebugEnabled()) {
logger.debug("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
}
doCreateBean
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#doCreateBean
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
throws BeanCreationException {
//实例化BeanWrapper是对Bean的包装
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
//选择合适的实例化策略来创建新的实例:工厂方法、构造函数自动注入、简单初始化
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
//获取早期对象,所谓的早期对象就是还没有初始化的对象
final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
mbd.resolvedTargetType = beanType;
// Allow post-processors to modify the merged bean definition.
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
//调用后置处理
applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Post-processing of merged bean definition failed", ex);
}
mbd.postProcessed = true;
}
}
//是否暴露早期对象,默认是
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
isSingletonCurrentlyInCreation(beanName));
if (earlySingletonExposure) {
if (logger.isDebugEnabled()) {
logger.debug("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
//把我们的早期对象包装成一个singletonFactory对象 该对象提供了一个getObject方法
addSingletonFactory(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
return getEarlyBeanReference(beanName, mbd, bean);
}
});
}
// Initialize the bean instance.
Object exposedObject = bean;
try {
//给我们的属性进行赋值(调用set方法进行赋值)
populateBean(beanName, mbd, instanceWrapper);
if (exposedObject != null) {
//初始化,动态代理也在这里生成
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<String>(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 " +
"'getBeanNamesOfType' 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;
}
initializeBean
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#initializeBean(java.lang.String, java.lang.Object, org.springframework.beans.factory.support.RootBeanDefinition)
protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
if (System.getSecurityManager() != null) {
AccessController.doPrivileged(new PrivilegedAction<Object>() {
@Override
public Object run() {
invokeAwareMethods(beanName, bean);
return null;
}
}, getAccessControlContext());
}
else {
//我们的bean实现了XXXAware接口进行方法的回调
invokeAwareMethods(beanName, bean);
}
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
//调用我们的bean的后置处理器的postProcessorsBeforeInitialization方法 注意@PostConstruct在这步处理调用
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
//调用初始化方法,比如实现了InitializingBean接口,回调InitializingBean的afterPropertiesSet()方法或者调用自定义的init方法
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()) {
//调用我们bean的后置处理器的PostProcessorsAfterInitialization方法
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
}
getBean的流程图如下