Ioc容器中的依赖注入-populateBean源码分析
这篇文章主要的就是分析在Bean对象创建完成之后的，怎样设置好Bean对象的依赖关系完成整个依赖注入过程，在完成依赖注入的过程中的依据是对BeanDefinition对象的解析
其实就是为了看到populateBean方法，这个方法是位于AbstractAutowireCapableBeanFactory类中
populateBean方法中的源码：
//这个方法的具体作用等待解析
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
//解析之后的BeanDefiinition如果为空,其结果还有propertyValues值就会抛出异常
if (bw == null) {
if (mbd.hasPropertyValues()) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
}
} else {
//否则就会就会调用bean的后置处理器遍历
boolean continueWithPropertyPopulation = true;
if (!mbd.isSynthetic() && this.hasInstantiationAwareBeanPostProcessors()) {
Iterator var5 = this.getBeanPostProcessors().iterator();
//这段代码主要就是看迭代器中是否有instance对象的值，有的话就会将标识符变为false
while(var5.hasNext()) {
//强制转换为BeanPostProcecssor
BeanPostProcessor bp = (BeanPostProcessor)var5.next();
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor)bp;
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
continueWithPropertyPopulation = false;
break;
}
}
}
}
//这里是对标识符结果进行
if (continueWithPropertyPopulation) {
PropertyValues pvs = mbd.hasPropertyValues() ? mbd.getPropertyValues() : null;
//开始进行依赖注入的过程，处理Autowire的注入
if (mbd.getResolvedAutowireMode() == 1 || mbd.getResolvedAutowireMode() == 2) {
MutablePropertyValues newPvs = new MutablePropertyValues((PropertyValues)pvs);
if (mbd.getResolvedAutowireMode() == 1) {
this.autowireByName(beanName, mbd, bw, newPvs);
}
if (mbd.getResolvedAutowireMode() == 2) {
this.autowireByType(beanName, mbd, bw, newPvs);
}
//这里对变量进行重定义
pvs = newPvs;
}
boolean hasInstAwareBpps = this.hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = mbd.getDependencyCheck() != 0;
PropertyDescriptor[] filteredPds = null;
//如果有bean后置处理器时，并且结果为null值，那么就会直接从BeanDefinition中直接调用方法获取
if (hasInstAwareBpps) {
if (pvs == null) {
pvs = mbd.getPropertyValues();
}
//遍历后置处理器的迭代器代码
Iterator var9 = this.getBeanPostProcessors().iterator();
while(var9.hasNext()) {
BeanPostProcessor bp = (BeanPostProcessor)var9.next();
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor)bp;
//获取到propertyValues中的值
PropertyValues pvsToUse = ibp.postProcessProperties((PropertyValues)pvs, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
if (filteredPds == null) {
//获取到依赖的检查的过滤器
filteredPds = this.filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
pvsToUse = ibp.postProcessPropertyValues((PropertyValues)pvs, filteredPds, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
return;
}
}
pvs = pvsToUse;
}
}
}
if (needsDepCheck) {
if (filteredPds == null) {
filteredPds = this.filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
this.checkDependencies(beanName, mbd, filteredPds, (PropertyValues)pvs);
}
if (pvs != null) {
//对属性进行注入
this.applyPropertyValues(beanName, mbd, bw, (PropertyValues)pvs);
}
}
}
}
下面就是对applyPropertyValues方法的源码解析
applyPropertyValues方法:
//对属性注入的方法分析
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
if (!pvs.isEmpty()) {
if (System.getSecurityManager() != null && bw instanceof BeanWrapperImpl) {
((BeanWrapperImpl)bw).setSecurityContext(this.getAccessControlContext());
}
//mutable--可变的
MutablePropertyValues mpvs = null;
List original;
if (pvs instanceof MutablePropertyValues) {
mpvs = (MutablePropertyValues)pvs;
//converted转变，转化
if (mpvs.isConverted()) {
try {
bw.setPropertyValues(mpvs);
return;
} catch (BeansException var18) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Error setting property values", var18);
}
}
original = mpvs.getPropertyValueList();
} else {
original = Arrays.asList(pvs.getPropertyValues());
}
//获取到类型转换
TypeConverter converter = this.getCustomTypeConverter();
if (converter == null) {
//变量重赋值
converter = bw;
}
//实例化这个BeanDefinitionValueResolver对象
BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, (TypeConverter)converter);
List<PropertyValue> deepCopy = new ArrayList(original.size());
boolean resolveNecessary = false;
Iterator var11 = original.iterator();
while(true) {
while(var11.hasNext()) {
PropertyValue pv = (PropertyValue)var11.next();
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 = this.convertForProperty(resolvedValue, propertyName, bw, (TypeConverter)converter);
}
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();
}
try {
//这里是发生依赖注入的地方，会在BeanWrapperImpl中完成
bw.setPropertyValues(new MutablePropertyValues(deepCopy));
return;
} catch (BeansException var19) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Error setting property values", var19);
}
}
}
}
//总结这个属性注入的方法的代码逻辑有点没有明白过来