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