文章目录
createBean方法
@Override
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.
// 解析beanName对应的Bean的类型,例如 org.springframework.beans.factory.config.BeanPostProcessor
Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
//如果resolvedClass存在,并且mbd的beanClass类型不是Class,并且mbd的beanClass不为空(代表beanClass存的是class的name)
if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
//是用mbd深拷贝一个新的RootBeanDefinition的副本;
mbdToUse = new RootBeanDefinition(mbd);
// 并且将解析的resolvedClass赋值给拷贝的对象,使用拷贝的副本用于后续操作
mbdToUse.setBeanClass(resolvedClass);
}
// Prepare method overrides.
try {
// 验证准备覆盖的方法(对override属性进行标记验证)
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.
// 实例化前处理,给InstantiationAwareBeanPostProcessors一个机会返回代理对象来代替真正的bean实例
Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
//如果bean不为空跳过spring默认的实例化过程,直接返回bean
if (bean != null) {
return bean;
}
}
catch (Throwable ex) {
throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,
"BeanPostProcessor before instantiation of bean failed", ex);
}
// 真正创建bean的方法
Object beanInstance = doCreateBean(beanName, mbdToUse, args);
if (logger.isDebugEnabled()) {
logger.debug("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
}
doCreateBean
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
throws BeanCreationException {
// Instantiate the bean.
// 新建bean的包装类
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
// 如果是工厂bean,需要先移除未完成的factoryBean实例的缓存
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
// 根据beanName,mbd,args使用对应的策略创建bean实例,并返回包装类BeanWrapper
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
// 拿到创建好的Bean实例
final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
// 拿到bean实例的类型
Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
mbd.resolvedTargetType = beanType;
// Allow post-processors to modify the merged bean definition.
// 允许后置处理器修改合并的bean定义
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
// 应用后置处理器MergedBeanDefinitionPostProcessor,允许修改MergedBeanDefinitio
//@Autowired注解正是通过这个方法实现注入类型的预解析
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.
// 判断是否需要提前曝光实例,是否是单例,循环依赖,是否正在创建
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");
}
// 提前曝光beanName的ObjectFactory用于解决循环依赖
addSingletonFactory(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
// 应用后置处理器SmartInstantiationAwareBeanPostProcessor
// 允许返回指定bean的早期引用，若没有则直接返回bean
return getEarlyBeanReference(beanName, mbd, bean);
}
});
}
// Initialize the bean instance.
//初始化bean
Object exposedObject = bean;
try {
//对bean进行属性填充,存在循环依赖,依赖其他bean的属性,会递归初始化依赖bean实例
populateBean(beanName, mbd, instanceWrapper);
if (exposedObject != null) {
// 初始化bean,执行BeanPostProcessor的postProcessBeforeInitialization方法
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) {
// 如果允许提前曝光实例,则进行循环依赖检查
Object earlySingletonReference = getSingleton(beanName, false);
// earlySingletonReference只有在当前解析的bean存在循环依赖的情况下才会不为空
if (earlySingletonReference != null) {
if (exposedObject == bean) {
// 如果exposedObject没有在initializeBean方法中被增强，则不影响之前的循环引用
exposedObject = earlySingletonReference;
}
else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
// 如果exposedObject在initializeBean方法中被增强 && 不允许在循环引用的情况下使用注入原始bean实例
// && 当前bean有被其他bean依赖
//拿到当前bean的所有依赖bean的名称的数组
String[] dependentBeans = getDependentBeans(beanName);
Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length);
for (String dependentBean : dependentBeans) {
// 尝试移除这些bean实例,因为这些bean依赖的bean已经被增强了,
if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
// 移除失败的加到actualDependentBeans
actualDependentBeans.add(dependentBean);
}
}
// 如果存在移除失败的，则抛出异常，因为存在bean依赖了“脏数据”
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 {
// 注册用于销毁的bean,执行销毁操作的有三种：自定义destroy方法、DisposableBean接口、DestructionAwareBeanPostProcessor
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
return exposedObject;
}
createBeanInstance创建bean实例
protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) {
// Make sure bean class is actually resolved at this point.
// 解析bean类型信息
Class<?> beanClass = resolveBeanClass(mbd, beanName);
if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
// beanClass不为空 && beanClass不是公开类（不是public修饰） && 该bean不允许访问非公共构造函数和方法，则抛异常
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
}
// 如果存在工厂方法则使用工厂方法创建bean
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) {
// 锁
synchronized (mbd.constructorArgumentLock) {
if (mbd.resolvedConstructorOrFactoryMethod != null) {
// 如果resolvedConstructorOrFactoryMethod缓存不为空,则将resolved标记为已解析
resolved = true;
// 根据constructorArgumentsResolved判断是否需要自动注入
autowireNecessary = mbd.constructorArgumentsResolved;
}
}
}
if (resolved) {
// 如果已经解析过,则使用resolvedConstructorOrFactoryMethod缓存里解析好的构造函数方法
if (autowireNecessary) {
// 需要自动注入，则执行构造函数自动注入
return autowireConstructor(beanName, mbd, null, null);
}
else {
// 使用默认的构造函数进行bean的实例化
return instantiateBean(beanName, mbd);
}
}
// Candidate constructors for autowiring?
// 应用后置处理器SmartInstantiationAwareBeanPostProcessor，拿到bean的候选构造函数
Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
if (ctors != null || mbd.getResolvedAutowireMode() == AUTOWIRE_CONSTRUCTOR ||
mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) {
// 如果ctors不为空 || mbd的注入方式为AUTOWIRE_CONSTRUCTOR || mdb定义了构造函数的参数值 || args不为空，则执行构造函数自动注入
return autowireConstructor(beanName, mbd, ctors, args);
}
// No special handling: simply use no-arg constructor.
// 没有特殊处理,使用默认的构造函数进行bean初始化
return instantiateBean(beanName, mbd);
}
就看一下简单通过构造函数进行bean初始化instantiateBean方法
protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
try {
Object beanInstance;
final BeanFactory parent = this;
if (System.getSecurityManager() != null) {
beanInstance = AccessController.doPrivileged(new PrivilegedAction<Object>() {
@Override
public Object run() {
return getInstantiationStrategy().instantiate(mbd, beanName, parent);
}
}, getAccessControlContext());
}
else {
// 获取创建bean实例的策略,调用策略的instantiate方法进行实例化
// 默认实例化cglib private InstantiationStrategy instantiationStrategy = new CglibSubclassingInstantiationStrategy();
beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent);
}
//把实例包装成BeanWrapper并且初始化一下beanWrapper的值
BeanWrapper bw = new BeanWrapperImpl(beanInstance);
initBeanWrapper(bw);
return bw;
}
catch (Throwable ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);
}
}
instantiate方法获取对应的策略去执行初始化方法
@Override
public Object instantiate(RootBeanDefinition bd, String beanName, BeanFactory owner) {
// Don't override the class with CGLIB if no overrides.
// 如果MethOverrides为空
if (bd.getMethodOverrides().isEmpty()) {
Constructor<?> constructorToUse;
synchronized (bd.constructorArgumentLock) {
// 获取bd.resolvedConstructorOrFactoryMethod已解析的构造器或工厂方法
constructorToUse = (Constructor<?>) bd.resolvedConstructorOrFactoryMethod;
//如果为空
if (constructorToUse == null) {
final Class<?> clazz = bd.getBeanClass();
// 如果是接口,抛出异常
if (clazz.isInterface()) {
throw new BeanInstantiationException(clazz, "Specified class is an interface");
}
try {
if (System.getSecurityManager() != null) {
constructorToUse = AccessController.doPrivileged(new PrivilegedExceptionAction<Constructor<?>>() {
@Override
public Constructor<?> run() throws Exception {
return clazz.getDeclaredConstructor((Class[]) null);
}
});
}
else {
//通过bean的类clazz来得到声明的构造函数
constructorToUse = clazz.getDeclaredConstructor((Class[]) null);
}
// 并赋值回给bd.resolvedConstructorOrFactoryMethod
bd.resolvedConstructorOrFactoryMethod = constructorToUse;
}
catch (Throwable ex) {
throw new BeanInstantiationException(clazz, "No default constructor found", ex);
}
}
}
// 通过BeanUtils方法实例化bean
return BeanUtils.instantiateClass(constructorToUse);
}
else {
// Must generate CGLIB subclass.
// 如果MethodOverrides不为空,生成cglib的子类
return instantiateWithMethodInjection(bd, beanName, owner);
}
}
BeanUtils.instantiateClass的方法就是通过Constructor构造实例
public static <T> T instantiateClass(Constructor<T> ctor, Object... args) throws BeanInstantiationException {
Assert.notNull(ctor, "Constructor must not be null");
try {
ReflectionUtils.makeAccessible(ctor);
return ctor.newInstance(args);
}
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());
}
}
这时候最初始的bean就被实例化了~
doCreateBean方法里面还有比较重要的方法populateBean
populateBean方法就是对bean属性进行赋值;
源码:
ByName(beanName, mbd, bw, newPvs);
}
// Add property values based on autowire by type if applicable.
// 根据类型注入
if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
}
//对变量的重新定义
pvs = newPvs;
}
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE);
if (hasInstAwareBpps || needsDepCheck) {
PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
if (hasInstAwareBpps) {
// 执行InstantiationAwareBeanPostProcessor的postProcessPropertyValues方法
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
if (pvs == null) {
return;
}
}
}
}
//对dependency-check属性的支持，默认是不校验
if (needsDepCheck) {
checkDependencies(beanName, mbd, filteredPds, pvs);
}
}
//对属性进行注入
applyPropertyValues(beanName, mbd, bw, pvs);
}
applyPropertyValues,真正进行属性赋值的地方
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
if (pvs == null || pvs.isEmpty()) {
return;
}
if (System.getSecurityManager() != null && bw instanceof BeanWrapperImpl) {
((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext());
}
MutablePropertyValues mpvs = null;
List<PropertyValue> original;
if (pvs instanceof MutablePropertyValues) {
// 如果mpvs中的值已经被转换为对应的类型，那么可以直接设置到beanWrapper中
mpvs = (MutablePropertyValues) pvs;
if (mpvs.isConverted()) {
// Shortcut: use the pre-converted values as-is.
try {
bw.setPropertyValues(mpvs);
return;
}
catch (BeansException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
}
}
original = mpvs.getPropertyValueList();
}
else {
// 如果pvs并不是使用MutablePropertyValues封装的类型，那么直接使用原始的属性获取方法
original = Arrays.asList(pvs.getPropertyValues());
}
TypeConverter converter = getCustomTypeConverter();
if (converter == null) {
converter = bw;
}
// 获取对应的解析器
BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
// Create a deep copy, resolving any references for values.
List<PropertyValue> deepCopy = new ArrayList<PropertyValue>(original.size());
boolean resolveNecessary = false;
// 遍历属性,将属性转换为对应类的属性类型
for (PropertyValue pv : original) {
if (pv.isConverted()) {
deepCopy.add(pv);
}
else {
String propertyName = pv.getName();
Object originalValue = pv.getValue();
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
Object convertedValue = resolvedValue;
boolean convertible = bw.isWritableProperty(propertyName) &&
!PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
if (convertible) {
convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter);
}
// Possibly store converted value in merged bean definition,
// in order to avoid re-conversion for every created bean instance.
if (resolvedValue == originalValue) {
if (convertible) {
pv.setConvertedValue(convertedValue);
}
deepCopy.add(pv);
}
else if (convertible && originalValue instanceof TypedStringValue &&
!((TypedStringValue) originalValue).isDynamic() &&
!(convertedValue instanceof Collection || ObjectUtils.isArray(convertedValue))) {
pv.setConvertedValue(convertedValue);
deepCopy.add(pv);
}
else {
resolveNecessary = true;
deepCopy.add(new PropertyValue(pv, convertedValue));
}
}
}
if (mpvs != null && !resolveNecessary) {
mpvs.setConverted();
}
// Set our (possibly massaged) deep copy.
try {
//通过反射将属性赋值,就不细看了,太复杂
bw.setPropertyValues(new MutablePropertyValues(deepCopy));
}
catch (BeansException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
}
}
//通过反射将属性赋值,就不细看了,太复杂
bw.setPropertyValues(new MutablePropertyValues(deepCopy));
最后一步通过BeanWrapper封装的方法进行属性赋值,也是通过反射,感兴趣的可以点进去看看~
doCreateBean方法里面还有比较重要的方法initializeBean
源码:
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 {
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;
}
initializeBean方法主要执行了一些aware接口(BeanNameAware,BeanFactoryAware);执行bean后置处理器的postProcessBeforeInitialization方法,然后就是实现了InitializingBean接口的afterPropertiesSet方法和配置的init方法了
invokeAwareMethods 执行三个aware接口方法
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);
}
}
}
applyBeanPostProcessorsBeforeInitialization,执行bean后置处理器的postProcessBeforeInitialization方法
@Override
public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
throws BeansException {
Object result = existingBean;
for (BeanPostProcessor processor : getBeanPostProcessors()) {
result = processor.postProcessBeforeInitialization(result, beanName);
if (result == null) {
return result;
}
}
return result;
}
invokeInitMethods init方法afterPropertiesSet方法
protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
throws Throwable {
//判断接口是否实现了InitializingBean接口
boolean isInitializingBean = (bean instanceof InitializingBean);
if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
if (logger.isDebugEnabled()) {
logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
}
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) {
//判断是否设置了init 方法
String initMethodName = mbd.getInitMethodName();
if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
!mbd.isExternallyManagedInitMethod(initMethodName)) {
//通过反射执行设置的init方法
invokeCustomInitMethod(beanName, bean, mbd);
}
}
}
