Spring DI源码跟踪小记

左手的ㄟ右手 2022-05-21 11:38 146阅读 0赞

*  1、开始 **AbstractBeanFactory.getBean()**

public Object getBean(String name) throws BeansException {
        return this.doGetBean(name, (Class)null, (Object[])null, false);
    }
    
    protected <T> T doGetBean(String name, Class<T> requiredType, final Object[] args, boolean typeCheckOnly) throws BeansException {
        final String beanName = this.transformedBeanName(name);
        Object sharedInstance = this.getSingleton(beanName);
        Object bean;
        if (sharedInstance != null && args == null) {
            // ... ...
        } else {
            // ... ...
            // ... ...
            if (mbd.isSingleton()) {
                sharedInstance = this.getSingleton(beanName, new ObjectFactory<Object>() {
                    public Object getObject() throws BeansException {
                        try {
                            // 创建bean
                            return AbstractBeanFactory.this.createBean(beanName, mbd, args);
                        } catch (BeansException var2) {
                            AbstractBeanFactory.this.destroySingleton(beanName);
                            throw var2;
                        }
                    }
                });
                bean = this.getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
            } else if (mbd.isPrototype()) {
                // ... ...
            } else {
                // ... ...
                } catch (IllegalStateException var20) {
                    throw new BeanCreationException(beanName, "Scope '" + scopeName + "' is not active for the current thread; " + "consider defining a scoped proxy for this bean if you intend to refer to it from a singleton", var20);
                }
            }
        }
    
        if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) {
            // ... ...
        } else {
            return bean;
        }
    }

*  2、**AbstractAutowireCapableBeanFactory\#createBean()**

protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
        // ... ...
    
        Object beanInstance;
        // ... ...
    
        beanInstance = this.doCreateBean(beanName, mbd, args);
        // ... ...
    
        return beanInstance;
    }
    
    protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, Object[] args) {
        BeanWrapper instanceWrapper = null;
        if (mbd.isSingleton()) {
            instanceWrapper = (BeanWrapper)this.factoryBeanInstanceCache.remove(beanName);
        }
    
        if (instanceWrapper == null) {
            // 返回Bean包装器
            instanceWrapper = this.createBeanInstance(beanName, mbd, args);
        }
    
        // ... ...
        Object exposedObject = bean;
    
        try {
            // 根据Bean包装器填充Bean实例
            this.populateBean(beanName, mbd, instanceWrapper);
            if (exposedObject != null) {
                // 初始化bean
                exposedObject = this.initializeBean(beanName, exposedObject, mbd);
            }
        } catch (Throwable var17) {
            // ... ...
        }
    
        // ... ...
        try {
            this.registerDisposableBeanIfNecessary(beanName, bean, mbd);
            return exposedObject;
        } catch (BeanDefinitionValidationException var16) {
            throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Invalid destruction signature", var16);
        }
    }
    
    protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) {
        Class beanClass = this.resolveBeanClass(mbd, beanName, new Class[0]);
        if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
            // ... ...
        } else if (mbd.getFactoryMethodName() != null) {
            return this.instantiateUsingFactoryMethod(beanName, mbd, args);
        } else {
            // 实例化Bean
            if (resolved) {
                return autowireNecessary ? this.autowireConstructor(beanName, mbd, (Constructor[])null, (Object[])null) : this.instantiateBean(beanName, mbd);
            } else {
                Constructor[] ctors = this.determineConstructorsFromBeanPostProcessors(beanClass, beanName);
                return ctors == null && mbd.getResolvedAutowireMode() != 3 && !mbd.hasConstructorArgumentValues() && ObjectUtils.isEmpty(args) ? this.instantiateBean(beanName, mbd) : this.autowireConstructor(beanName, mbd, ctors, args);
            }
        }
    }
    
    protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
        try {
            Object beanInstance;
            // 实例化Bean
            if (System.getSecurityManager() != null) {
                beanInstance = AccessController.doPrivileged(new PrivilegedAction<Object>() {
                    public Object run() {
                        return AbstractAutowireCapableBeanFactory.this.getInstantiationStrategy().instantiate(mbd, beanName, AbstractAutowireCapableBeanFactory.this);
                    }
                }, this.getAccessControlContext());
            } else {
                beanInstance = this.getInstantiationStrategy().instantiate(mbd, beanName, this);
            }
            // 返回Bean包装器
            BeanWrapper bw = new BeanWrapperImpl(beanInstance);
            this.initBeanWrapper(bw);
            return bw;
        } catch (Throwable var6) {
            throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Instantiation of bean failed", var6);
        }
    }

**总结：**  
1、调用 AbstractBeanFactory获取Bean  
2、跳到 AbstractAutowireCapableBeanFactory.createBean()  
3、调用 createBeanInstance 创建Bean包装器 BeanWrapper  
4、再使用BeanWrapper填充Bean  
5、再使用initializeBean 初始化Bean 然后返回