在前一篇我们一起分析了 getBean Spring 中对象创建的过程，今天我们继续分析 AbstractAutowireCapableBeanFactory#populateBean 方法 Spring 对 Bean 对象进行属性填充（其实也是我们说的自动注入的过程）
获取字段信息
获取 Bean 的字段信息
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
查找 Bean 的模式
通常查找 Bean 的模式有两种 AUTOWIRE_BY_NAME 或者 AUTOWIRE_BY_NAME
if (resolvedAutowireMode == AUTOWIRE_BY_NAME || resolvedAutowireMode == AUTOWIRE_BY_TYPE) { MutablePropertyValues newPvs = new MutablePropertyValues(pvs); // Add property values based on autowire by name if applicable. if (resolvedAutowireMode == AUTOWIRE_BY_NAME) { autowireByName(beanName, mbd, bw, newPvs); } // Add property values based on autowire by type if applicable. if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) { autowireByType(beanName, mbd, bw, newPvs); } pvs = newPvs; }
1. 通过 Bean 名称查找
通过 BeanName 进行 Bean 的查询然后添加到 pvs 中。
protected void autowireByName( String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) { // 获取非基础类型的属性 String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw); for (String propertyName : propertyNames) { // 是否存在这个 beanName if (containsBean(propertyName)) { // 获取 bean Object bean = getBean(propertyName); pvs.add(propertyName, bean); registerDependentBean(propertyName, beanName); if (logger.isTraceEnabled()) { logger.trace("Added autowiring by name from bean name '" + beanName + "' via property '" + propertyName + "' to bean named '" + propertyName + "'"); } } else { if (logger.isTraceEnabled()) { logger.trace("Not autowiring property '" + propertyName + "' of bean '" + beanName + "' by name: no matching bean found"); } } } }
2. 通过 Bean 类型查找
protected void autowireByType( String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) { TypeConverter converter = getCustomTypeConverter(); if (converter == null) { converter = bw; } Set<String> autowiredBeanNames = new LinkedHashSet<>(4); String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw); for (String propertyName : propertyNames) { try { // 获取需要注入属性的 PropertyDescriptor PropertyDescriptor pd = bw.getPropertyDescriptor(propertyName); // Don't try autowiring by type for type Object: never makes sense, // even if it technically is a unsatisfied, non-simple property. // 排除 Object 类型 if (Object.class != pd.getPropertyType()) { // 获取 geng 方法 MethodParameter methodParam = BeanUtils.getWriteMethodParameter(pd); // Do not allow eager init for type matching in case of a prioritized post-processor. boolean eager = !(bw.getWrappedInstance() instanceof PriorityOrdered); DependencyDescriptor desc = new AutowireByTypeDependencyDescriptor(methodParam, eager); // 解析指定 beanName 的属性所匹配的值，并把解析到的属性名称存储在 autowiredBeanNames 中 // 当属性存在过个封装 bean 时将会找到所有匹配的 bean 并将其注入 Object autowiredArgument = resolveDependency(desc, beanName, autowiredBeanNames, converter); if (autowiredArgument != null) { pvs.add(propertyName, autowiredArgument); } // 循环 autowiredBeanNames for (String autowiredBeanName : autowiredBeanNames) { registerDependentBean(autowiredBeanName, beanName); if (logger.isTraceEnabled()) { logger.trace("Autowiring by type from bean name '" + beanName + "' via property '" + propertyName + "' to bean named '" + autowiredBeanName + "'"); } } autowiredBeanNames.clear(); } } catch (BeansException ex) { throw new UnsatisfiedDependencyException(mbd.getResourceDescription(), beanName, propertyName, ex); } } }
3. 几个重要的方法
- unsatisfiedNonSimpleProperties
就是类型为对象类型的属性，但是这里并不是将所有的对象类型都都会找到，比如 8 个原始类型，String 类型 ，Number类型、Date类型、URL类型、URI类型等都会被忽略
protected String[] unsatisfiedNonSimpleProperties(AbstractBeanDefinition mbd, BeanWrapper bw) { Set<String> result = new TreeSet<>(); PropertyValues pvs = mbd.getPropertyValues(); PropertyDescriptor[] pds = bw.getPropertyDescriptors(); for (PropertyDescriptor pd : pds) { if (pd.getWriteMethod() != null && !isExcludedFromDependencyCheck(pd) && !pvs.contains(pd.getName()) && !BeanUtils.isSimpleProperty(pd.getPropertyType())) { result.add(pd.getName()); } } return StringUtils.toStringArray(result); }
- registerDependentBean
保存属性注入的映射关系
public void registerDependentBean(String beanName, String dependentBeanName) { String canonicalName = canonicalName(beanName); synchronized (this.dependentBeanMap) { Set<String> dependentBeans = this.dependentBeanMap.computeIfAbsent(canonicalName, k -> new LinkedHashSet<>(8)); if (!dependentBeans.add(dependentBeanName)) { return; } } synchronized (this.dependenciesForBeanMap) { Set<String> dependenciesForBean = this.dependenciesForBeanMap.computeIfAbsent(dependentBeanName, k -> new LinkedHashSet<>(8)); dependenciesForBean.add(canonicalName); } }
