Spring5.0源码学习系列之浅谈BeanFactory创建
Spring5.0源码学习系列之浅谈BeanFactory创建过程
系列文章目录
提示:Spring源码学习专栏链接
@TOC
博客前言介绍
提示:在上一章的学习中,我们简单了解了Spring IoC容器启动初始化的主流程,不过并没有详细解释,因为代码比较复杂,没有做长篇大论,所以本文接着学习BenFactory的创建过程,学习源码建议带着疑问去学,一点点跟,时间积累之后就可以串起来
提示:以下是本篇文章正文内容,下面案例可供参考
一、获取BeanFactory主流程
在前面的学习中,#refresh是IoC容器创建很关键的主线,在代码里,可以找到obtainFreshBeanFactory
这个比较关键的方法,这个方法就是BeanFactory的创建过程方法,本文ClassPathXmlApplicationContext
为准,进行源码的学习,上篇博客是以AnnotationApplicationContext
为准进行简单的分析,本文继续比较详细的讲述
实验环境:
maven项目,需要加上pom配置:
5.0.9.RELEASE
如果是gradle环境,可以直接在Spring框架project里新增一个module,具体可以参考教程:加上对应的配置
文章图片
在这里插入图片描述
SpringBean.java:
package com.example.bean;
import org.springframework.beans.factory.InitializingBean;
/**
*
*SpringBean
*
*
*
* @author mazq
* 修改记录
*修改后版本:修改人:修改日期: 2020/11/05 10:50修改内容:
*
*/
public class SpringBean implements InitializingBean {public SpringBean(){
System.out.println("SpringBean构造函数");
}@Override
public void afterPropertiesSet() throws Exception {
System.out.println("SpringBean afterPropertiesSet");
}
}
applicationContext.xml:
测试类,使用ClassPathXmlApplicationContext
package com.example;
import com.example.bean.SpringBean;
import org.springframework.context.support.ClassPathXmlApplicationContext;
/**
*
*TestController
*
*
*
* @author mazq
* 修改记录
*修改后版本:修改人:修改日期: 2020/11/05 10:22修改内容:
*
*/
public class TestApplication {
public static void testClassPathXmlApplicationContext() {
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:applicationContext.xml");
SpringBeanspringBean = context.getBean(SpringBean.class);
System.out.println(springBean);
}public static void main(String[] args) {
// 测试ClassPathXmlApplicationContext
testClassPathXmlApplicationContext();
}
}
在SpringBean 打断点,debug进行调试:找到#refresh方法
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在这里插入图片描述
obtainFreshBeanFactory示例:
/**
* Tell the subclass to refresh the internal bean factory.
* @return the fresh BeanFactory instance
* @see #refreshBeanFactory()
* @see #getBeanFactory()
*/
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
// 创建BeanFactory
refreshBeanFactory();
// 返回refreshBeanFactory方法创建好的BeanFactory
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
然后refreshBeanFactory
是由哪个基类实现的?我们找来一张uml类图:
文章图片
在这里插入图片描述
从图可以知道
ClassPathXmlApplicationContext
通过
AbstractRefreshableApplicationContext
实现
AbstractApplicationContext
,所以
refreshBeanFactory
是
AbstractRefreshableApplicationContext#refreshBeanFactory
ok,所以主体的路线,就可以熟悉,用uml时序图表示:
文章图片
在这里插入图片描述 二、refreshBeanFactory创建过程
refreshBeanFactory
方法是BeanFactory的创建过程,接着跟
org.springframework.context.support.AbstractRefreshableApplicationContext#refreshBeanFactory
代码如下(示例):
/**
* This implementation performs an actual refresh of this context's underlying
* bean factory, shutting down the previous bean factory (if any) and
* initializing a fresh bean factory for the next phase of the context's lifecycle.
*/
@Override
protected final void refreshBeanFactory() throws BeansException {
// 先判断是否有BeanFactory
if (hasBeanFactory()) {
// destroy Beans
destroyBeans();
// 关闭BeanFactory
closeBeanFactory();
}
try {
// 实例化DefaultListableBeanFactory
DefaultListableBeanFactory beanFactory = createBeanFactory();
// 设置序列化id
beanFactory.setSerializationId(getId());
// 定义BeanFactory的一些属性(是否允许Bean覆盖,是否允许循环依赖)
customizeBeanFactory(beanFactory);
// 加载应用中的BeanDefinition
loadBeanDefinitions(beanFactory);
this.beanFactory = beanFactory;
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
{@link org.springframework.context.support.AbstractXmlApplicationContext#loadBeanDefinitions}
/**
* Loads the bean definitions via an XmlBeanDefinitionReader.
* @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
* @see #initBeanDefinitionReader
* @see #loadBeanDefinitions
*/
@Override
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// Create a new XmlBeanDefinitionReader for the given BeanFactory.
// 给BeanFactory实例化一个XmlBeanDefinitionReader实例
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// Configure the bean definition reader with this context's
// resource loading environment.
beanDefinitionReader.setEnvironment(this.getEnvironment());
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
// Allow a subclass to provide custom initialization of the reader,
// then proceed with actually loading the bean definitions.
// 给子类提供初始化XmlBeanDefinitionReader的模板方法
initBeanDefinitionReader(beanDefinitionReader);
// 重点在这,继续跟
loadBeanDefinitions(beanDefinitionReader);
}// org.springframework.context.support.AbstractXmlApplicationContext#loadBeanDefinitions(org.springframework.beans.factory.support.DefaultListableBeanFactory)
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
Resource[] configResources = getConfigResources();
if (configResources != null) {
// 继续跟
reader.loadBeanDefinitions(configResources);
}
String[] configLocations = getConfigLocations();
if (configLocations != null) {
reader.loadBeanDefinitions(configLocations);
}
}
{@link org.springframework.beans.factory.support.AbstractBeanDefinitionReader#loadBeanDefinitions}
@Override
public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {
Assert.notNull(resources, "Resource array must not be null");
int counter = 0;
// 变量资源对象,加载BeanDefinition
for (Resource resource : resources) {
// 在这里,经过debug,调到XmlBeanDefinitionReader.loadBeanDefinitions(resource)
counter += loadBeanDefinitions(resource);
}
// 返回统计数量,表示总共有多少个BeanDefinition
return counter;
}
XmlBeanDefinitionReader
类
{@link org.springframework.beans.factory.xml.XmlBeanDefinitionReader#loadBeanDefinitions}
@Override
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
return loadBeanDefinitions(new EncodedResource(resource));
}// 省略.../**
* Load bean definitions from the specified XML file.
* @param encodedResource the resource descriptor for the XML file,
* allowing to specify an encoding to use for parsing the file
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of loading or parsing errors
*/
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (logger.isInfoEnabled()) {
logger.info("Loading XML bean definitions from " + encodedResource);
}
// 用ThreadLocal存放资源对象,目的是保证线程安全
Set
{@link org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader#registerBeanDefinitions}
/**
* This implementation parses bean definitions according to the "spring-beans" XSD
* (or DTD, historically).
* Opens a DOM Document;
then initializes the default settings
* specified at the {@code
bean元素处理,本文挑beana元素的处理进行讲述:
/**
* Process the given bean element, parsing the bean definition
* and registering it with the registry.
*/
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//解析Bean元素为BeanDefinition,再通过BeanDefinitionHolder封装成BeanDefinitionHolder对象
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
// 有自定义属性会进行相应的解析
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// Register the final decorated instance.
// BeanDefinition的注册过程
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
}
catch (BeanDefinitionStoreException ex) {
getReaderContext().error("Failed to register bean definition with name '" +
bdHolder.getBeanName() + "'", ele, ex);
}
// Send registration event.
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}
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