Spring依赖处理过程源码分析
- AbstractAutowireCapableBeanFactory#doCreateBean创建Bean
- AbstractAutowireCapableBeanFactory#populateBean属性的核心注入方法
- InstantiationAwareBeanPostProcessor#postProcessProperties用于给bean处理值注入，@Autowire就在这个过程处理注入
- InjectionMetadata#inject-->AutowiredMethodElement#inject
- resolveDependency
- doResolveDependency
AbstractAutowireCapableBeanFactory#doCreateBean创建Bean
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd,
final @Nullable Object[] args) throws BeanCreationException {
// 1. 实例化Bean，构造器注入或工厂方法注入
BeanWrapper instanceWrapper = createBeanInstance(beanName, mbd, args);
// 2. 后置处理器修改Bean的定义BeanDefinition：bdp#postProcessMergedBeanDefinition
applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
// 3. 提前将Bean暴露到IoC容器中，用于解决循环依赖
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences
&& isSingletonCurrentlyInCreation(beanName));
if (earlySingletonExposure) {
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
}
// 4. populateBean属性注入的核心方法，initializeBean则执行bean初始化方法
Object exposedObject = bean;
populateBean(beanName, mbd, instanceWrapper);
exposedObject = initializeBean(beanName, exposedObject, mbd);
// 5. 注册bean的依赖关系，用于bean销毁用
registerDisposableBeanIfNecessary(beanName, bean, mbd);
return exposedObject;
}
AbstractAutowireCapableBeanFactory#populateBean属性的核心注入方法
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
// 1. 判断是否需要进行属性注入：ibp#postProcessAfterInstantiation
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
return;
}
}
}
}
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
// 2. 自动注入：包括名称注入和类型注入
int resolvedAutowireMode = mbd.getResolvedAutowireMode();
if (resolvedAutowireMode == AUTOWIRE_BY_NAME || resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
// 2.1 自动根据名称注入
if (resolvedAutowireMode == AUTOWIRE_BY_NAME) {
autowireByName(beanName, mbd, bw, newPvs);
}
// 2.2 自动根据类型注入
if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
}
pvs = newPvs;
}
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE);
// 3. 注解注入：后置处理器ibp#postProcessProperties，大名鼎鼎的@Autowired就是在这处理的。
PropertyDescriptor[] filteredPds = null;
if (hasInstAwareBpps) {
if (pvs == null) {
pvs = mbd.getPropertyValues();
}
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
PropertyValues pvsToUse = ibp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
pvsToUse = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
return;
}
}
pvs = pvsToUse;
}
}
}
// 4. 依赖检查，循环依赖...
if (needsDepCheck) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
checkDependencies(beanName, mbd, filteredPds, pvs);
}
// 5. 手动依赖注入
if (pvs != null) {
applyPropertyValues(beanName, mbd, bw, pvs);
}
}
InstantiationAwareBeanPostProcessor#postProcessProperties用于给bean处理值注入，@Autowire就在这个过程处理注入
@Override
public PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) {
// 这里获取目标bean每个需要注入的依赖,metadata会包含一组元素，每个元素对应一个目标bean :
// 1. @Autowired/@Value 注解的属性 或者
// 2. @Autowired/@Value 注解的方法参数
InjectionMetadata metadata = findAutowiringMetadata(beanName, bean.getClass(), pvs);
try {
// 执行依赖注入
metadata.inject(bean, beanName, pvs);
}
catch (BeanCreationException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanCreationException(beanName, "Injection of autowired dependencies failed",
ex);
}
return pvs;
}
InjectionMetadata#inject-->AutowiredMethodElement#inject
public void inject(Object target, @Nullable String beanName, @Nullable PropertyValues pvs)
throws Throwable {
Collection<InjectedElement> checkedElements = this.checkedElements;
Collection<InjectedElement> elementsToIterate =
(checkedElements != null ? checkedElements : this.injectedElements);
if (!elementsToIterate.isEmpty()) {
// 遍历目标bean每个需要注入的成员属性依赖或者成员方法参数依赖，执行相应的依赖注入
for (InjectedElement element : elementsToIterate) {
if (logger.isTraceEnabled()) {
logger.trace("Processing injected element of bean '" + beanName + "': " + element);
}
element.inject(target, beanName, pvs);
}
}
}
@Override
protected void inject(Object bean, @Nullable String beanName, @Nullable PropertyValues pvs)
throws Throwable {
Field field = (Field) this.member;
Object value;
if (this.cached) {
value = resolvedCachedArgument(beanName, this.cachedFieldValue);
}
else {
DependencyDescriptor desc = new DependencyDescriptor(field, this.required);
desc.setContainingClass(bean.getClass());
Set<String> autowiredBeanNames = new LinkedHashSet<>(1);
Assert.state(beanFactory != null, "No BeanFactory available");
TypeConverter typeConverter = beanFactory.getTypeConverter();
try {
// 依赖解析使用 beanFactory#resolveDependency
value = beanFactory.resolveDependency(desc, beanName, autowiredBeanNames,
typeConverter);
}
catch (BeansException ex) {
throw new UnsatisfiedDependencyException(null, beanName,
new InjectionPoint(field), ex);
}
synchronized (this) {
if (!this.cached) {
if (value != null || this.required) {
this.cachedFieldValue = desc;
registerDependentBeans(beanName, autowiredBeanNames);
if (autowiredBeanNames.size() == 1) {
String autowiredBeanName = autowiredBeanNames.iterator().next();
if (beanFactory.containsBean(autowiredBeanName) &&
beanFactory.isTypeMatch(autowiredBeanName, field.getType())) {
this.cachedFieldValue = new ShortcutDependencyDescriptor(
desc, autowiredBeanName, field.getType());
}
}
}
else {
this.cachedFieldValue = null;
}
this.cached = true;
}
}
}
if (value != null) {
ReflectionUtils.makeAccessible(field);
field.set(bean, value);
}
}
Spring中依赖处理从DefaultListableBeanFactory的resolveDependency方法开始处理
描述注入信息的类DependencyDescriptor
public class DependencyDescriptor extends InjectionPoint implements Serializable {
//被注入的声明类
private final Class<?> declaringClass;
//方法注入的方法名
@Nullable
private String methodName;
//对应的参数
@Nullable
private Class<?>[] parameterTypes;
//参数索引
private int parameterIndex;
//如果所包装的是成员属性，则这里记录该成员属性的名称
@Nullable
private String fieldName;
//是否必要依赖
private final boolean required;
//是否是懒加载
private final boolean eager;
//嵌套级别
private int nestingLevel = 1;
//通常和declaringClass一样
@Nullable
private Class<?> containingClass;
//泛型处理
@Nullable
private transient volatile ResolvableType resolvableType;
//依赖 TypeDescriptor 的缓存
@Nullable
private transient volatile TypeDescriptor typeDescriptor;
}
resolveDependency方法
@Override
@Nullable
public Object resolveDependency(DependencyDescriptor descriptor, @Nullable String requestingBeanName,
@Nullable Set<String> autowiredBeanNames, @Nullable TypeConverter typeConverter) throws BeansException {
descriptor.initParameterNameDiscovery(getParameterNameDiscoverer());
if (Optional.class == descriptor.getDependencyType()) {
//如:@Autowired private Optional<Rumenz> rumenzOpt;
return createOptionalDependency(descriptor, requestingBeanName);
}
else if (ObjectFactory.class == descriptor.getDependencyType() ||
ObjectProvider.class == descriptor.getDependencyType()) {
//如:@Autowired private ObjectProvider<Rumenz> obj;
return new DependencyObjectProvider(descriptor, requestingBeanName);
}
else if (javaxInjectProviderClass == descriptor.getDependencyType()) {
//如:@Inject private Rumenz rumenz;
return new Jsr330Factory().createDependencyProvider(descriptor, requestingBeanName);
}
else {
Object result = getAutowireCandidateResolver().getLazyResolutionProxyIfNecessary(
descriptor, requestingBeanName);
if (result == null) {
result = doResolveDependency(descriptor, requestingBeanName, autowiredBeanNames, typeConverter);
}
return result;
}
}
doResolveDependency真正的依赖注入
@Nullable
public Object doResolveDependency(DependencyDescriptor descriptor, @Nullable String beanName,
@Nullable Set<String> autowiredBeanNames, @Nullable TypeConverter typeConverter) throws BeansException {
InjectionPoint previousInjectionPoint = ConstructorResolver.setCurrentInjectionPoint(descriptor);
try {
Object shortcut = descriptor.resolveShortcut(this);
if (shortcut != null) {
return shortcut;
}
Class<?> type = descriptor.getDependencyType();
Object value = getAutowireCandidateResolver().getSuggestedValue(descriptor);
if (value != null) {
if (value instanceof String) {
String strVal = resolveEmbeddedValue((String) value);
BeanDefinition bd = (beanName != null && containsBean(beanName) ?
getMergedBeanDefinition(beanName) : null);
value = evaluateBeanDefinitionString(strVal, bd);
}
TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
try {
return converter.convertIfNecessary(value, type, descriptor.getTypeDescriptor());
}
catch (UnsupportedOperationException ex) {
// A custom TypeConverter which does not support TypeDescriptor resolution...
return (descriptor.getField() != null ?
converter.convertIfNecessary(value, type, descriptor.getField()) :
converter.convertIfNecessary(value, type, descriptor.getMethodParameter()));
}
}
//注入的是一组Bean Array,List,Map
Object multipleBeans = resolveMultipleBeans(descriptor, beanName, autowiredBeanNames, typeConverter);
if (multipleBeans != null) {
return multipleBeans;
}
//根据类型查找相应的Bean
Map<String, Object> matchingBeans = findAutowireCandidates(beanName, type, descriptor);
if (matchingBeans.isEmpty()) {
if (isRequired(descriptor)) {
raiseNoMatchingBeanFound(type, descriptor.getResolvableType(), descriptor);
}
return null;
}
String autowiredBeanName;
Object instanceCandidate;
//如果Bean的个数大于1
if (matchingBeans.size() > 1) {
//选择primary的Bean autowiredBeanName就是查找到需要注入的Bean
autowiredBeanName = determineAutowireCandidate(matchingBeans, descriptor);
if (autowiredBeanName == null) {
if (isRequired(descriptor) || !indicatesMultipleBeans(type)) {
return descriptor.resolveNotUnique(descriptor.getResolvableType(), matchingBeans);
}
else {
// In case of an optional Collection/Map, silently ignore a non-unique case:
// possibly it was meant to be an empty collection of multiple regular beans
// (before 4.3 in particular when we didn't even look for collection beans).
return null;
}
}
instanceCandidate = matchingBeans.get(autowiredBeanName);
}
else {
// We have exactly one match.
Map.Entry<String, Object> entry = matchingBeans.entrySet().iterator().next();
autowiredBeanName = entry.getKey();
instanceCandidate = entry.getValue();
}
if (autowiredBeanNames != null) {
autowiredBeanNames.add(autowiredBeanName);
}
if (instanceCandidate instanceof Class) {
instanceCandidate = descriptor.resolveCandidate(autowiredBeanName, type, this);
}
Object result = instanceCandidate;
if (result instanceof NullBean) {
if (isRequired(descriptor)) {
raiseNoMatchingBeanFound(type, descriptor.getResolvableType(), descriptor);
}
result = null;
}
if (!ClassUtils.isAssignableValue(type, result)) {
throw new BeanNotOfRequiredTypeException(autowiredBeanName, type, instanceCandidate.getClass());
}
return result;
}
finally {
ConstructorResolver.setCurrentInjectionPoint(previousInjectionPoint);
}
}
原文: https://rumenz.com/rumenbiji/Spring-dependency-processing.html
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