这一讲分析spring bean属性注入代码populateBean,源码分析如下

    /**
* Populate the bean instance in the given BeanWrapper with the property values
* from the bean definition.
* 丰富bean实例属性
* @param beanName the name of the bean
* @param mbd the bean definition for the bean
* @param bw BeanWrapper with bean instance
*/
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
PropertyValues pvs = mbd.getPropertyValues(); if (bw == null) {
if (!pvs.isEmpty()) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
}
else {
// Skip property population phase for null instance.
return;
}
} // Give any InstantiationAwareBeanPostProcessors the opportunity to modify the
// state of the bean before properties are set. This can be used, for example,
// to support styles of field injection.
// 属性设置前调用处理器
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;
} if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs); // Add property values based on autowire by name if applicable.
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
autowireByName(beanName, mbd, bw, newPvs);
} // Add property values based on autowire by type if applicable.
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
} pvs = newPvs;
} boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE); // 设置bean属性
if (hasInstAwareBpps || needsDepCheck) {
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);
}
} applyPropertyValues(beanName, mbd, bw, pvs);
}

debug过程中我们知道,总共有7个BeanPostProcessor

对于@Autowired,@Value注解注入的属性值,AutowiredAnnotationBeanPostProcessor会处理。我们进一步分析AutowiredAnnotationBeanPostProcessor注入属性的代码

    /**
* Autowired属性注入
* @author coshaho
* @param pvs
* @param pds 注入属性配置,方法中没有使用
* @param bean bean实例
* @param beanName
* @return
* @throws BeanCreationException
*/
public PropertyValues postProcessPropertyValues(
PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeanCreationException { // 获取注入属性配置信息
InjectionMetadata metadata = findAutowiringMetadata(beanName, bean.getClass(), pvs);
try {
// 属性注入
metadata.inject(bean, beanName, pvs);
}
catch (BeanCreationException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanCreationException(beanName, "Injection of autowired dependencies failed", ex);
}
return pvs;
}
public void inject(Object target, @Nullable String beanName, @Nullable PropertyValues pvs) throws Throwable {
// 获取待注入的属性队列
Collection<InjectedElement> checkedElements = this.checkedElements;
Collection<InjectedElement> elementsToIterate =
(checkedElements != null ? checkedElements : this.injectedElements);
if (!elementsToIterate.isEmpty()) {
boolean debug = logger.isDebugEnabled();
for (InjectedElement element : elementsToIterate) {
if (debug) {
logger.debug("Processing injected element of bean '" + beanName + "': " + element);
}
// 属性注入
element.inject(target, beanName, pvs);
}
}
}

InjectionMetadata是bean注入属性配置,InjectionElement是单个的注入属性配置,InjectionElement.inject则为单个属性注入方法。InjectionElement.inject则调用的DefaultListableBeanFactory.doResolveDependency方法获取属性值

    @Override
protected void inject(Object bean, @Nullable String beanName, @Nullable PropertyValues pvs) throws Throwable {
Field field = (Field) this.member;
Object value;
if (this.cached) {
value = resolvedCachedArgument(beanName, this.cachedFieldValue);
}
else {
// 获取注入属性配置:属性名称,类名称
DependencyDescriptor desc = new DependencyDescriptor(field, this.required);
desc.setContainingClass(bean.getClass());
Set<String> autowiredBeanNames = new LinkedHashSet<>(1);
Assert.state(beanFactory != null, "No BeanFactory available");
TypeConverter typeConverter = beanFactory.getTypeConverter();
try {
// 获取属性值
value = beanFactory.resolveDependency(desc, beanName, autowiredBeanNames, typeConverter);
}
catch (BeansException ex) {
throw new UnsatisfiedDependencyException(null, beanName, new InjectionPoint(field), ex);
}
synchronized (this) {
if (!this.cached) {
if (value != null || this.required) {
this.cachedFieldValue = desc;
registerDependentBeans(beanName, autowiredBeanNames);
if (autowiredBeanNames.size() == 1) {
String autowiredBeanName = autowiredBeanNames.iterator().next();
if (beanFactory.containsBean(autowiredBeanName)) {
if (beanFactory.isTypeMatch(autowiredBeanName, field.getType())) {
this.cachedFieldValue = new ShortcutDependencyDescriptor(
desc, autowiredBeanName, field.getType());
}
}
}
}
else {
this.cachedFieldValue = null;
}
this.cached = true;
}
}
}
if (value != null) {
ReflectionUtils.makeAccessible(field);
// 反射设置属性
field.set(bean, value);
}
} 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) {
// 获取注入值
result = doResolveDependency(descriptor, requestingBeanName, autowiredBeanNames, typeConverter);
}
return result;
}
}
    public Object doResolveDependency(DependencyDescriptor descriptor, @Nullable String beanName,
@Nullable Set<String> autowiredBeanNames, @Nullable TypeConverter typeConverter) throws BeansException { // 注入属性配置
InjectionPoint previousInjectionPoint = ConstructorResolver.setCurrentInjectionPoint(descriptor);
try {
Object shortcut = descriptor.resolveShortcut(this);
if (shortcut != null) {
return shortcut;
} // 注入属性类型
Class<?> type = descriptor.getDependencyType();
// 如果是Value注解,这里可以直接获取注解String值
Object value = getAutowireCandidateResolver().getSuggestedValue(descriptor);
if (value != null) {
if (value instanceof String) {
String strVal = resolveEmbeddedValue((String) value);
BeanDefinition bd = (beanName != null && containsBean(beanName) ? getMergedBeanDefinition(beanName) : null);
// Value可以是一个表达式,表达式需要进行计算
value = evaluateBeanDefinitionString(strVal, bd);
}
TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
// 此处对Value进行类型转换
return (descriptor.getField() != null ?
converter.convertIfNecessary(value, type, descriptor.getField()) :
converter.convertIfNecessary(value, type, descriptor.getMethodParameter()));
} Object multipleBeans = resolveMultipleBeans(descriptor, beanName, autowiredBeanNames, typeConverter);
if (multipleBeans != null) {
return multipleBeans;
} // 获取{bean名称:bean类型} Map,bean名称默认为类名称
Map<String, Object> matchingBeans = findAutowireCandidates(beanName, type, descriptor);
if (matchingBeans.isEmpty()) {
if (isRequired(descriptor)) {
raiseNoMatchingBeanFound(type, descriptor.getResolvableType(), descriptor);
}
return null;
} String autowiredBeanName;
Object instanceCandidate; if (matchingBeans.size() > 1) {
autowiredBeanName = determineAutowireCandidate(matchingBeans, descriptor);
if (autowiredBeanName == null) {
if (isRequired(descriptor) || !indicatesMultipleBeans(type)) {
return descriptor.resolveNotUnique(type, matchingBeans);
}
else {
// In case of an optional Collection/Map, silently ignore a non-unique case:
// possibly it was meant to be an empty collection of multiple regular beans
// (before 4.3 in particular when we didn't even look for collection beans).
return null;
}
}
instanceCandidate = matchingBeans.get(autowiredBeanName);
}
else {
// We have exactly one match.
Map.Entry<String, Object> entry = matchingBeans.entrySet().iterator().next();
autowiredBeanName = entry.getKey();
instanceCandidate = entry.getValue();
} if (autowiredBeanNames != null) {
autowiredBeanNames.add(autowiredBeanName);
}
// 关键方法,bean名称不为空,通过bean名称,bean类型获取注入bean
if (instanceCandidate instanceof Class) {
instanceCandidate = descriptor.resolveCandidate(autowiredBeanName, type, this);
}
Object result = instanceCandidate;
if (result instanceof NullBean) {
if (isRequired(descriptor)) {
raiseNoMatchingBeanFound(type, descriptor.getResolvableType(), descriptor);
}
result = null;
}
if (!ClassUtils.isAssignableValue(type, result)) {
throw new BeanNotOfRequiredTypeException(autowiredBeanName, type, instanceCandidate.getClass());
}
return result;
}
finally {
ConstructorResolver.setCurrentInjectionPoint(previousInjectionPoint);
}
}

这里descriptor.resolveCandidate正好调用了bean创建方法。需要注意的是,autowire注入默认采用bean名称注入,bean名称默认为类名,首字母并不小写

Spring源码阅读(六)的更多相关文章

  1. Bean实例化(Spring源码阅读)-我们到底能走多远系列(33)

    我们到底能走多远系列(33) 扯淡: 各位:    命运就算颠沛流离   命运就算曲折离奇   命运就算恐吓着你做人没趣味   别流泪 心酸 更不应舍弃   ... 主题: Spring源码阅读还在继 ...

  2. 初始化IoC容器(Spring源码阅读)

    初始化IoC容器(Spring源码阅读) 我们到底能走多远系列(31) 扯淡: 有个问题一直想问:各位你们的工资剩下来会怎么处理?已婚的,我知道工资永远都是不够的.未婚的你们,你们是怎么分配工资的? ...

  3. Spring源码阅读-ApplicationContext体系结构分析

    目录 继承层次图概览 ConfigurableApplicationContext分析 AbstractApplicationContext GenericApplicationContext Gen ...

  4. Sping学习笔记(一)----Spring源码阅读环境的搭建

    idea搭建spring源码阅读环境 安装gradle Github下载Spring源码 新建学习spring源码的项目 idea搭建spring源码阅读环境 安装gradle 在官网中下载gradl ...

  5. Spring源码阅读笔记02:IOC基本概念

    上篇文章中我们介绍了准备Spring源码阅读环境的两种姿势,接下来,我们就要开始探寻这个著名框架背后的原理.Spring提供的最基本最底层的功能是bean容器,这其实是对IoC思想的应用,在学习Spr ...

  6. Spring源码阅读 之 配置的读取,解析

    在上文中我们已经知道了Spring如何从我们给定的位置加载到配置文件,并将文件包装成一个Resource对象.这篇文章我们将要探讨的就是,如何从这个Resouce对象中加载到我们的容器?加载到容器后又 ...

  7. 搭建 Spring 源码阅读环境

    前言 有一个Spring源码阅读环境是学习Spring的基础.笔者借鉴了网上很多搭建环境的方法,也尝试了很多,接下来总结两种个人认为比较简便实用的方法.读者可根据自己的需要自行选择. 方法一:搭建基础 ...

  8. Spring源码阅读系列总结

    最近一段时间,粗略的查看了一下Spring源码,对Spring的两大核心和Spring的组件有了更深入的了解.同时在学习Spring源码时,得了解一些设计模式,不然阅读源码还是有一定难度的,所以一些重 ...

  9. Spring源码阅读笔记

    前言 作为一个Java开发者,工作了几年后,越发觉力有点不从心了,技术的世界实在是太过于辽阔了,接触的东西越多,越感到前所未有的恐慌. 每天捣鼓这个捣鼓那个,结果回过头来,才发现这个也不通,那个也不精 ...

  10. idea构建spring源码阅读环境

    注:由于文章不是一次性完成,下文中的test1目录和test目录应为同一个目录. (一)安装git和Gradle Spring项目托管在github之上,基于Gradle来构建项目.所以要想搭建Spr ...

随机推荐

  1. Scala笔记

    定义包 package com.runoob { class HelloWorld } 引用包 import java.awt.Color // 引入Color import java.awt._ / ...

  2. import Vue form 'vue’的意思

    1.import Vue form ‘vue’ 写全的话是import Vue from ‘…/nodemouls/vue/list/vue.js’: 此时在webpack.base.conf.js中 ...

  3. MySQL 5.6 Index Condition Pushdown

    ICP(index condition pushdown)是mysql利用索引(二级索引)元组和筛字段在索引中的where条件从表中提取数据记录的一种优化操作.ICP的思想是:存储引擎在访问索引的时候 ...

  4. 如何代码隐藏email而用户又能看到

    我们有时在网站上留一个邮箱,然后漫天垃圾邮件,非常苦恼,这是因为爬虫通过代码匹配收集网页上的邮箱,那么有没办法代码隐藏email而用户又能看到呢?其实不会很难,如果你的网站是用wordpress搭建, ...

  5. dbdeployer 快速安装MySQL8.0各测试环境

    Linux系统必须安装有Go语言: 下载最新的包:https://github.com/datacharmer/dbdeployer/releases     解压:  tar -xzf dbdepl ...

  6. Python3学习之路~6.8 多态

    多态性(polymorphisn)是允许你将父对象设置成为和一个或更多的他的子对象相等的技术,赋值之后,父对象就可以根据当前赋值给它的子对象的特性以不同的方式运作.简单的说,就是一句话:允许将子类类型 ...

  7. 【剑指offer】部分思路整理

    题目 LL今天心情特别好,因为他去买了一副扑克牌,发现里面居然有2个大王,2个小王(一副牌原本是54张^_^)...他随机从中抽出了5张牌,想测测自己的手气,看看能不能抽到顺子,如果抽到的话,他决定去 ...

  8. vue监听滚动事件 实现某元素吸顶或者固定位置显示

    https://blog.csdn.net/wang1006008051/article/details/78003974 1.监听滚动事件 利用VUE写一个在控制台打印当前的scrollTop, 首 ...

  9. 网络编程——socket编程

    一.客户端/服务端架构 1.硬件C/S架构(打印机) 2.软件C/S架构 互联网企业处处是C/S架构 C/S架构与socket的关系:学习socket就是为了完成C/S架构的开发 二.OSI七层 一个 ...

  10. openvpn-客户端配置文件

    ############################################## # 针对多个客户端的OpenVPN 2.0 的客户端配置文件示例 # # 该配置文件可以被多个客户端使用, ...