Spring DI源码分析5

本文主要是介绍Spring DI源码分析5，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

本篇主要是创建Bean后的属性注入

给bean设置属性

	protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
		if (bw == null) {
			if (mbd.hasPropertyValues()) {
				throw new BeanCreationException(
						mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
			}
			else {
				// Skip property population phase for null instance.
				return;
			}
		}

		//属性注入
		boolean continueWithPropertyPopulation = true;

		if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
			for (BeanPostProcessor bp : getBeanPostProcessors()) {
				if (bp instanceof InstantiationAwareBeanPostProcessor) {
					InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
					if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
						continueWithPropertyPopulation = false;
						break;
					}
				}
			}
		}

		if (!continueWithPropertyPopulation) {
			return;
		}
		//获取要为bean设置的属性值
		PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);

		//对依赖注入处理，处理autowiring自动装配的依赖注入	通过名称 或者 通过类型
		if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
				mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
			MutablePropertyValues newPvs = new MutablePropertyValues(pvs);

			//根据Bean名称进行autowiring自动装配处理
			if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
				autowireByName(beanName, mbd, bw, newPvs);
			}

			//根据Bean类型进行autowiring自动装配处理
			if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
				autowireByType(beanName, mbd, bw, newPvs);
			}

			pvs = newPvs;
		}

		//对非autowiring的属性进行依赖注入处理
		boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
		boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);

		if (hasInstAwareBpps || needsDepCheck) {
			if (pvs == null) {
				pvs = mbd.getPropertyValues();
			}
			PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
			if (hasInstAwareBpps) {
				for (BeanPostProcessor bp : getBeanPostProcessors()) {
					if (bp instanceof InstantiationAwareBeanPostProcessor) {
						InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
						pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
						if (pvs == null) {
							return;
						}
					}
				}
			}
			if (needsDepCheck) {
				checkDependencies(beanName, mbd, filteredPds, pvs);
			}
		}

		if (pvs != null) {
			//对属性进行注入，和上面的自动注入不冲突，上面的判断会将两个操作互斥
			applyPropertyValues(beanName, mbd, bw, pvs);
		}
	}

通过名字依赖注入

	protected void autowireByName(
			String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) {

		//获取非简单类型的属性，
		String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw);
		for (String propertyName : propertyNames) {
			//如果Spring IOC容器中包含指定名称的Bean
			if (containsBean(propertyName)) {
				//调用getBean方法向IOC容器索取指定名称的Bean实例，进行属性的初始化和依赖注入
				Object bean = getBean(propertyName);
				//为指定名称的属性赋予属性值
				pvs.add(propertyName, bean);
				//指定名称属性注册依赖Bean名称，进行属性依赖注入
				registerDependentBean(propertyName, beanName);
				if (logger.isDebugEnabled()) {
					logger.debug("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");
				}
			}
		}
	}

获得所有的非简单属性

	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);
	}

简单属性

	public static boolean isSimpleProperty(Class<?> clazz) {
		Assert.notNull(clazz, "Class must not be null");
		return isSimpleValueType(clazz) || (clazz.isArray() && isSimpleValueType(clazz.getComponentType()));
	}

	
	//简单属性
	public static boolean isSimpleValueType(Class<?> clazz) {
		return (ClassUtils.isPrimitiveOrWrapper(clazz) || clazz.isEnum() ||
				CharSequence.class.isAssignableFrom(clazz) ||
				Number.class.isAssignableFrom(clazz) ||
				Date.class.isAssignableFrom(clazz) ||
				URI.class == clazz || URL.class == clazz ||
				Locale.class == clazz || Class.class == clazz);
	}

通过类型依赖注入

protected void autowireByType(
			String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) {

		//获取用户定义的类型转换器
		TypeConverter converter = getCustomTypeConverter();
		if (converter == null) {
			converter = bw;
		}

		//存放解析的要注入的属性
		Set<String> autowiredBeanNames = new LinkedHashSet<>(4);
		String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw);
		for (String propertyName : propertyNames) {
			try {
				//获取属性名称的属性描述器
				PropertyDescriptor pd = bw.getPropertyDescriptor(propertyName);
				//不对Object类型的属性进行autowiring自动依赖注入
				if (Object.class != pd.getPropertyType()) {
					//获取属性的写方法(setter方法)
					MethodParameter methodParam = BeanUtils.getWriteMethodParameter(pd);
					//优先处理postProcessor，不允许bean初始化
					boolean eager = !PriorityOrdered.class.isInstance(bw.getWrappedInstance());
					//创建一个要被注入的依赖描述
					DependencyDescriptor desc = new AutowireByTypeDependencyDescriptor(methodParam, eager);
					//解析依赖，返回所有要被注入的Bean对象
					Object autowiredArgument = resolveDependency(desc, beanName, autowiredBeanNames, converter);
					if (autowiredArgument != null) {
						//为属性赋值所引用的对象
						pvs.add(propertyName, autowiredArgument);
					}
					for (String autowiredBeanName : autowiredBeanNames) {
						//指定名称属性注册依赖Bean名称，进行属性依赖注入
						registerDependentBean(autowiredBeanName, beanName);
						if (logger.isDebugEnabled()) {
							logger.debug("Autowiring by type from bean name '" + beanName + "' via property '" +
									propertyName + "' to bean named '" + autowiredBeanName + "'");
						}
					}
					//释放已自动注入的属性
					autowiredBeanNames.clear();
				}
			}
			catch (BeansException ex) {
				throw new UnsatisfiedDependencyException(mbd.getResourceDescription(), beanName, propertyName, ex);
			}
		}
	}

解析依赖

public Object resolveDependency(DependencyDescriptor descriptor, @Nullable String requestingBeanName,
			@Nullable Set<String> autowiredBeanNames, @Nullable TypeConverter typeConverter) throws BeansException {

		descriptor.initParameterNameDiscovery(getParameterNameDiscoverer());
		if (Optional.class == descriptor.getDependencyType()) {
			return createOptionalDependency(descriptor, requestingBeanName);
		}
		else if (ObjectFactory.class == descriptor.getDependencyType() ||
				ObjectProvider.class == descriptor.getDependencyType()) {
			return new DependencyObjectProvider(descriptor, requestingBeanName);
		}
		else if (javaxInjectProviderClass == descriptor.getDependencyType()) {
			return new Jsr330ProviderFactory().createDependencyProvider(descriptor, requestingBeanName);
		}
		else {
			Object result = getAutowireCandidateResolver().getLazyResolutionProxyIfNecessary(
					descriptor, requestingBeanName);
			if (result == null) {
				result = doResolveDependency(descriptor, requestingBeanName, autowiredBeanNames, typeConverter);
			}
			return result;
		}
	}

设置属性

protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
		if (pvs.isEmpty()) {
			return;
		}

		//封装属性值
		MutablePropertyValues mpvs = null;
		List<PropertyValue> original;

		if (System.getSecurityManager() != null) {
			if (bw instanceof BeanWrapperImpl) {
				//设置安全上下文，JDK安全机制
				((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext());
			}
		}

		if (pvs instanceof MutablePropertyValues) {
			mpvs = (MutablePropertyValues) pvs;
			//属性值已经转换
			if (mpvs.isConverted()) {
				try {
					//为实例化对象设置属性值
					bw.setPropertyValues(mpvs);
					return;
				}
				catch (BeansException ex) {
					throw new BeanCreationException(
							mbd.getResourceDescription(), beanName, "Error setting property values", ex);
				}
			}
			//获取属性值对象的原始类型值
			original = mpvs.getPropertyValueList();
		}
		else {
			original = Arrays.asList(pvs.getPropertyValues());
		}

		//获取用户自定义的类型转换
		TypeConverter converter = getCustomTypeConverter();
		if (converter == null) {
			converter = bw;
		}
		//创建一个Bean定义属性值解析器，将Bean定义中的属性值解析为Bean实例对象的实际值
		BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);

		//为属性的解析值创建一个深拷贝，将拷贝的数据注入到实例对象中
		List<PropertyValue> deepCopy = new ArrayList<>(original.size());
		boolean resolveNecessary = false;
		for (PropertyValue pv : original) {
			//属性值不需要转换
			if (pv.isConverted()) {
				deepCopy.add(pv);
			}
			//属性值需要转换
			else {
				String propertyName = pv.getName();
				//原始的属性值，即转换之前的属性值
				Object originalValue = pv.getValue();
				//转换属性值
				Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
				//转换之后的属性值
				Object convertedValue = resolvedValue;
				//属性值是否可以转换
				boolean convertible = bw.isWritableProperty(propertyName) &&
						!PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
				if (convertible) {
					//使用用户自定义的类型转换器转换属性值
					convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter);
				}
				//存储转换后的属性值，避免每次属性注入时的转换工作
				if (resolvedValue == originalValue) {
					if (convertible) {
						//设置属性转换之后的值
						pv.setConvertedValue(convertedValue);
					}
					deepCopy.add(pv);
				}
				//属性是可转换的，且属性原始值是字符串类型，且属性的原始类型值不是
				//动态生成的字符串，且属性的原始值不是集合或者数组类型
				else if (convertible && originalValue instanceof TypedStringValue &&
						!((TypedStringValue) originalValue).isDynamic() &&
						!(convertedValue instanceof Collection || ObjectUtils.isArray(convertedValue))) {
					pv.setConvertedValue(convertedValue);
					//重新封装属性的值
					deepCopy.add(pv);
				}
				else {
					resolveNecessary = true;
					deepCopy.add(new PropertyValue(pv, convertedValue));
				}
			}
		}
		if (mpvs != null && !resolveNecessary) {
			//标记属性值已经转换过
			mpvs.setConverted();
		}

		//进行属性依赖注入
		try {
			bw.setPropertyValues(new MutablePropertyValues(deepCopy));
		}
		catch (BeansException ex) {
			throw new BeanCreationException(
					mbd.getResourceDescription(), beanName, "Error setting property values", ex);
		}
	}

调用bean的初始化方法，定义的initmethod

protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
		//JDK的安全机制验证权限
		if (System.getSecurityManager() != null) {
			//实现PrivilegedAction接口的匿名内部类
			AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
				invokeAwareMethods(beanName, bean);
				return null;
			}, getAccessControlContext());
		}
		else {
			//为Bean实例对象包装相关属性，如名称，类加载器，所属容器等信息
			invokeAwareMethods(beanName, bean);
		}

		Object wrappedBean = bean;
		//bean后置处理器，bean初始化前的处理
		if (mbd == null || !mbd.isSynthetic()) {
			wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
		}

		//调用Bean实例对象初始化的方法，类中的initMethod
		try {
			invokeInitMethods(beanName, wrappedBean, mbd);
		}
		catch (Throwable ex) {
			throw new BeanCreationException(
					(mbd != null ? mbd.getResourceDescription() : null),
					beanName, "Invocation of init method failed", ex);
		}
		//bean后置处理器，bean初始化后的操作
		if (mbd == null || !mbd.isSynthetic()) {
			wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
		}

		return wrappedBean;
	}
	//填充包装属性
	private void invokeAwareMethods(final String beanName, final Object bean) {
		if (bean instanceof Aware) {
			if (bean instanceof BeanNameAware) {
				((BeanNameAware) bean).setBeanName(beanName);
			}
			if (bean instanceof BeanClassLoaderAware) {
				ClassLoader bcl = getBeanClassLoader();
				if (bcl != null) {
					((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
				}
			}
			if (bean instanceof BeanFactoryAware) {
				((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
			}
		}
	}
	
	//调用initmethod初始化方法
	protected void invokeInitMethods(String beanName, final Object bean, @Nullable RootBeanDefinition mbd)
			throws Throwable {

		boolean isInitializingBean = (bean instanceof InitializingBean);
		if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
			if (logger.isDebugEnabled()) {
				logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
			}
			if (System.getSecurityManager() != null) {
				try {
					AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {
						((InitializingBean) bean).afterPropertiesSet();
						return null;
					}, getAccessControlContext());
				}
				catch (PrivilegedActionException pae) {
					throw pae.getException();
				}
			}
			else {
				((InitializingBean) bean).afterPropertiesSet();
			}
		}

		if (mbd != null && bean.getClass() != NullBean.class) {
			String initMethodName = mbd.getInitMethodName();
			if (StringUtils.hasLength(initMethodName) &&
					!(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
					!mbd.isExternallyManagedInitMethod(initMethodName)) {
				invokeCustomInitMethod(beanName, bean, mbd);
			}
		}
	}
	
	//调用自定义的initmethod
	protected void invokeCustomInitMethod(String beanName, final Object bean, RootBeanDefinition mbd)
			throws Throwable {

		String initMethodName = mbd.getInitMethodName();
		Assert.state(initMethodName != null, "No init method set");
		final Method initMethod = (mbd.isNonPublicAccessAllowed() ?
				BeanUtils.findMethod(bean.getClass(), initMethodName) :
				ClassUtils.getMethodIfAvailable(bean.getClass(), initMethodName));

		if (initMethod == null) {
			if (mbd.isEnforceInitMethod()) {
				throw new BeanDefinitionValidationException("Couldn't find an init method named '" +
						initMethodName + "' on bean with name '" + beanName + "'");
			}
			else {
				if (logger.isDebugEnabled()) {
					logger.debug("No default init method named '" + initMethodName +
							"' found on bean with name '" + beanName + "'");
				}
				// Ignore non-existent default lifecycle methods.
				return;
			}
		}

		if (logger.isDebugEnabled()) {
			logger.debug("Invoking init method  '" + initMethodName + "' on bean with name '" + beanName + "'");
		}

		if (System.getSecurityManager() != null) {
			AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
				ReflectionUtils.makeAccessible(initMethod);
				return null;
			});
			try {
				AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () ->
					initMethod.invoke(bean), getAccessControlContext());
			}
			catch (PrivilegedActionException pae) {
				InvocationTargetException ex = (InvocationTargetException) pae.getException();
				throw ex.getTargetException();
			}
		}
		else {
			try {
				//反射调用initmethod
				ReflectionUtils.makeAccessible(initMethod);
				initMethod.invoke(bean);
			}
			catch (InvocationTargetException ex) {
				throw ex.getTargetException();
			}
		}
	}

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