我们先来看下spring如何手动初始化一个对象
ClassPathResource res = new ClassPathResource("beans.xml");
DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(factory);
reader.loadBeanDefinitions(res);
User user=(User) factory.getBean("user");
所以我们先从DefaultListableBeanFactory开始了解 AbstractBeanFactory
public <T> T getBean(String name, Class<T> requiredType, Object... args) throws BeansException {
return doGetBean(name, requiredType, args, false);
}
protected <T> T doGetBean(
final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
throws BeansException {
1.去掉&
final String beanName = transformedBeanName(name);
protected String transformedBeanName(String name) {
return canonicalName(BeanFactoryUtils.transformedBeanName(name));
}
2.如果是单例且存在，就直接取过来
Object bean;
//
Object sharedInstance = getSingleton(beanName);
if (sharedInstance != null && args == null) {
....
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
3.如果已经创建，抛出异常
else {
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
4.在父BeanFactory查找
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);
}
}
5.创建标记，（用于清除）
if (!typeCheckOnly) {
markBeanAsCreated(beanName);
}
6.寻找bean定义信息，并针对bean定义进行验证
try {
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);
7.处理依赖信息，这里会针对xml定义中的depends-on进行处理
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
for (String dependsOnBean : dependsOn) {
if (isDependent(beanName, dependsOnBean)) {
....
registerDependentBean(dependsOnBean, beanName);
getBean(dependsOnBean);
}
}
具体通过这个私有方法来解决依赖的 假设A依赖于B，那么在创建A之前，必须保证B先被创建。 在创建了B之后，这里会进行依赖信息存储。后面在递归调用一下，不过依赖关系反过来。 dependentBeanMap放 A->［B,C,D］ （A所依赖的B,C,D）
private boolean isDependent(String beanName, String dependentBeanName, Set<String> alreadySeen) {
if (alreadySeen != null && alreadySeen.contains(beanName)) {
return false;
}
String canonicalName = canonicalName(beanName);
Set<String> dependentBeans = this.dependentBeanMap.get(canonicalName);
if (dependentBeans == null) {
return false;
}
if (dependentBeans.contains(dependentBeanName)) {
return true;
}
for (String transitiveDependency : dependentBeans) {
if (alreadySeen == null) {
alreadySeen = new HashSet<String>();
}
alreadySeen.add(beanName);
if (isDependent(transitiveDependency, dependentBeanName, alreadySeen)) {
return true;
}
}
return false;
}
单例模式就调用getSingleton(String beanName, ObjectFactory<?> singletonFactory)
// 单例
if (mbd.isSingleton()) {
....
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {
....
synchronized (this.singletonObjects) {
Object singletonObject = this.singletonObjects.get(beanName);
....
beforeSingletonCreation(beanName);
....
singletonObject = singletonFactory.getObject();
....
addSingleton(beanName, singletonObject);
}
return (singletonObject != NULL_OBJECT ? singletonObject : null);
}
}
原型模式
else if (mbd.isPrototype()) {
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
其他模式，比如scope=request
else {
String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(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);
}
....
}
}
....
}
8.无论哪种模式都会进入AbstractAutowireCapableBeanFactory的createBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
....
RootBeanDefinition mbdToUse = mbd;
// 解析beanDefinition，以确保bean定义中的class可以被正确解析
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();
}
....
try {
// 如果实现了InstantiationAwareBeanPostProcessor就先postProcessBeforeInstantiation(Class<?> beanClass, String beanName)->postProcessAfterInitialization(Object bean, String beanName)
Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
if (bean != null) {
return bean;
}
}
....
Object beanInstance = doCreateBean(beanName, mbdToUse, args);
....
}
return beanInstance;
9.Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
....
if (exposedObject != null) {
exposedObject = initializeBean(beanName, exposedObject, mbd);
}
....
10.Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd)
if (System.getSecurityManager() != null) {
AccessController.doPrivileged(new PrivilegedAction<Object>() {
@Override
public Object run() {
//setBeanName#BeanNameAware
//->setBeanClassLoader#BeanClassLoaderAware
//->setBeanFactory#BeanFactoryAware
invokeAwareMethods(beanName, bean);
return null;
}
}, getAccessControlContext());
}
else {
invokeAwareMethods(beanName, bean);
}
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
//->postProcessBeforeInitialization#BeanPostProcessor
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
//->afterPropertiesSet#InitializingBean
invokeInitMethods(beanName, wrappedBean, mbd);
}
....
if (mbd == null || !mbd.isSynthetic()) {
//->postProcessAfterInitialization#BeanPostProcessor
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
private void invokeAwareMethods(final String beanName, final Object bean) {
if (bean instanceof Aware) {
if (bean instanceof BeanNameAware) {
((BeanNameAware) bean).setBeanName(beanName);
}
if (bean instanceof BeanClassLoaderAware) {
((BeanClassLoaderAware) bean).setBeanClassLoader(getBeanClassLoader());
}
if (bean instanceof BeanFactoryAware) {
((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
}
}
}
protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
throws Throwable {
boolean isInitializingBean = (bean instanceof InitializingBean);
if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
....
if (System.getSecurityManager() != null) {
try {
AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
@Override
public Object run() throws Exception {
((InitializingBean) bean).afterPropertiesSet();
return null;
}
}, getAccessControlContext());
}
catch (PrivilegedActionException pae) {
throw pae.getException();
}
}
else {
((InitializingBean) bean).afterPropertiesSet();
}
}
if (mbd != null) {
String initMethodName = mbd.getInitMethodName();
if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
!mbd.isExternallyManagedInitMethod(initMethodName)) {
invokeCustomInitMethod(beanName, bean, mbd);
}
}
}
postProcessBeforeInstantiation(Class<?> beanClass, String beanName)#InstantiationAwareBeanPostProcessor ->postProcessAfterInitialization(Object bean, String beanName)#InstantiationAwareBeanPostProcessor ->setBeanName#BeanNameAware ->setBeanClassLoader#BeanClassLoaderAware ->setBeanFactory#BeanFactoryAware ->postProcessBeforeInitialization#BeanPostProcessor ->afterPropertiesSet#InitializingBean ->postProcessAfterInitialization#BeanPostProcessor
public class InitAndDestroySeqBean implements InitializingBean,DisposableBean,BeanPostProcessor,InstantiationAwareBeanPostProcessor {
public InitAndDestroySeqBean() {
System.out.println("构造方法");
}
@PostConstruct
public void postConstruct(){
System.out.println("@PostConstruct");
}
@Override public void afterPropertiesSet() throws Exception {
System.out.println("afterPropertiesSet()#InitializingBean");
}
public void initMethod(){
System.out.println("init-method");
}
@PreDestroy
public void preDestroy(){
System.out.println("@PreDestroy");
}
@Override public void destroy() throws Exception {
System.out.println("destroy()#DisposableBean");
}
public void destroyMethod(){
System.out.println("destroy-method");
}
@Override public Object postProcessBeforeInitialization(Object bean, String beanName)
throws BeansException {
System.out.println("postProcessBeforeInitialization(Object bean, String beanName)#BeanPostProcessor");
return bean;
}
@Override public Object postProcessAfterInitialization(Object bean, String beanName)
throws BeansException {
System.out.println("postProcessAfterInitialization(Object bean, String beanName)#BeanPostProcessor");
return bean;
}
@Override public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName)
throws BeansException {
System.out.println("postProcessBeforeInstantiation(Class<?> beanClass, String beanName)#InstantiationAwareBeanPostProcessor");
return null;
}
@Override public boolean postProcessAfterInstantiation(Object bean, String beanName)
throws BeansException {
System.out.println("postProcessAfterInstantiation(Object bean, String beanName)#InstantiationAwareBeanPostProcessor");
return false;
}
@Override public PropertyValues postProcessPropertyValues(PropertyValues pvs, PropertyDescriptor[] pds,
Object bean, String beanName) throws BeansException {
System.out.println("postProcessPropertyValues(PropertyValues pvs, PropertyDescriptor[] pds,\n"
+ " Object bean, String beanName)#InstantiationAwareBeanPostProcessor");
return null;
}
}
20170308:11:34:52.866 [main] INFO Using TestExecutionListeners: [org.springframework.test.context.web.ServletTestExecutionListener@49c43f4e, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener@290dbf45, org.springframework.test.context.support.DependencyInjectionTestExecutionListener@12028586, org.springframework.test.context.support.DirtiesContextTestExecutionListener@17776a8, org.springframework.test.context.transaction.TransactionalTestExecutionListener@69a10787, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener@2d127a61]20170308:11:34:52.972 [main] INFO Loading XML bean definitions from URL [file:/Users/dsc/IdeaProjects/firDemo/firdemo/web/target/classes/init.xml] 20170308:11:34:53.105 [main] INFO Refreshing org.springframework.context.support.GenericApplicationContext@2b4a2ec7: startup date [Wed Mar 08 11:34:53 CST 2017]; root of context hierarchy 构造方法 @PostConstruct afterPropertiesSet()#InitializingBean init-method postProcessBeforeInstantiation(Class<?> beanClass, String beanName)#InstantiationAwareBeanPostProcessor postProcessAfterInstantiation(Object bean, String beanName)#InstantiationAwareBeanPostProcessor postProcessBeforeInitialization(Object bean, String beanName)#BeanPostProcessor postProcessAfterInitialization(Object bean, String beanName)#BeanPostProcessor postProcessBeforeInstantiation(Class<?> beanClass, String beanName)#InstantiationAwareBeanPostProcessor postProcessAfterInstantiation(Object bean, String beanName)#InstantiationAwareBeanPostProcessor postProcessBeforeInitialization(Object bean, String beanName)#BeanPostProcessor postProcessAfterInitialization(Object bean, String beanName)#BeanPostProcessor postProcessAfterInstantiation(Object bean, String beanName)#InstantiationAwareBeanPostProcessor postProcessBeforeInitialization(Object bean, String beanName)#BeanPostProcessor postProcessAfterInitialization(Object bean, String beanName)#BeanPostProcessor 20170308:11:34:53.286 [Thread-0] INFO Closing org.springframework.context.support.GenericApplicationContext@2b4a2ec7: startup date [Wed Mar 08 11:34:53 CST 2017]; root of context hierarchy @PreDestroy destroy()#DisposableBean destroy-method
