找到spring依赖注入的源码

最新推荐文章于 2025-12-09 15:16:31 发布

原创最新推荐文章于 2025-12-09 15:16:31 发布 · 221 阅读

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本文深入探讨了Spring框架中依赖注入的实现机制，详细解析了AutowiredAnnotationBeanPostProcessor类中的关键方法，包括postProcessProperties、inject及resolveFieldValue等，并介绍了类型转换器在依赖注入过程中的作用。

首先定位到AutowiredAnnotationBeanPostProcessor类下的postProcessProperties方法

public PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) {
    InjectionMetadata metadata = this.findAutowiringMetadata(beanName, bean.getClass(), pvs);
    try {
        //在这里依赖注入
        metadata.inject(bean, beanName, pvs);
        return pvs;
    } catch (BeanCreationException var6) {
        throw var6;
    } catch (Throwable var7) {
        throw new BeanCreationException(beanName, "Injection of autowired dependencies failed", var7);
    }
}

InjectionMetadata的inject方法

public void inject(Object target, @Nullable String beanName, @Nullable PropertyValues pvs) throws Throwable {
    Collection<InjectionMetadata.InjectedElement> checkedElements = this.checkedElements;
    Collection<InjectionMetadata.InjectedElement> elementsToIterate = checkedElements != null ? checkedElements : this.injectedElements;
    if (!((Collection)elementsToIterate).isEmpty()) {
        Iterator var6 = ((Collection)elementsToIterate).iterator();

        while(var6.hasNext()) {
            InjectionMetadata.InjectedElement element = (InjectionMetadata.InjectedElement)var6.next();
            //这里注入一个属性
            element.inject(target, beanName, pvs);
        }
    }

}

然后是AutowiredAnnotationBeanPostProcessor类下的inject方法

protected void inject(Object bean, @Nullable String beanName, @Nullable PropertyValues pvs) throws Throwable {
    Field field = (Field)this.member;
    Object value;
    if (this.cached) {
        try {
            value = AutowiredAnnotationBeanPostProcessor.this.resolvedCachedArgument(beanName, this.cachedFieldValue);
        } catch (NoSuchBeanDefinitionException var7) {
            value = this.resolveFieldValue(field, bean, beanName);
        }
    } else {
        value = this.resolveFieldValue(field, bean, beanName);
    }

    if (value != null) {
        ReflectionUtils.makeAccessible(field);
        field.set(bean, value);
    }

}

然后是AutowiredAnnotationBeanPostProcessor类下的resolveFieldValue方法，就是这里涉及到类型转换器

@Nullable
private Object resolveFieldValue(Field field, Object bean, @Nullable String beanName) {
    DependencyDescriptor desc = new DependencyDescriptor(field, this.required);
    desc.setContainingClass(bean.getClass());
    Set<String> autowiredBeanNames = new LinkedHashSet(1);
    Assert.state(AutowiredAnnotationBeanPostProcessor.this.beanFactory != null, "No BeanFactory available");
    //这里得到一个类型转换器
    TypeConverter typeConverter = AutowiredAnnotationBeanPostProcessor.this.beanFactory.getTypeConverter();

    Object value;
    try {
        //利用类型转换器解析得到值
        value = AutowiredAnnotationBeanPostProcessor.this.beanFactory.resolveDependency(desc, beanName, autowiredBeanNames, typeConverter);
    } catch (BeansException var12) {
        throw new UnsatisfiedDependencyException((String)null, beanName, new InjectionPoint(field), var12);
    }

    synchronized(this) {
        if (!this.cached) {
            Object cachedFieldValue = null;
            if (value != null || this.required) {
                cachedFieldValue = desc;
                AutowiredAnnotationBeanPostProcessor.this.registerDependentBeans(beanName, autowiredBeanNames);
                if (autowiredBeanNames.size() == 1) {
                    String autowiredBeanName = (String)autowiredBeanNames.iterator().next();
                    if (AutowiredAnnotationBeanPostProcessor.this.beanFactory.containsBean(autowiredBeanName) && AutowiredAnnotationBeanPostProcessor.this.beanFactory.isTypeMatch(autowiredBeanName, field.getType())) {
                        cachedFieldValue = new AutowiredAnnotationBeanPostProcessor.ShortcutDependencyDescriptor(desc, autowiredBeanName, field.getType());
                    }
                }
            }

            this.cachedFieldValue = cachedFieldValue;
            this.cached = true;
        }

        return value;
    }
}

在这里插入图片描述
可以看到有53个类型转换器