6-Spring-IoC容器初始化

概述

• 步骤
  • Resource定位
  • Document载入
  • BeanDefinition注册

XmlBeanFactory

• Deprecated

ClassPathResource resource = new ClassPathResource("spring-test.xml");
DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(factory);
reader.loadBeanDefinitions(resource);
System.out.println(factory.getBean("bean1"));

ClassPathXmlApplicationContext

入口

• ClassPathXmlApplicationContext构造方法
  • super(parent)
    • CPXAC.resourcePatternResolver.resourceLoader = CPXAC
    • CPXAC.parentApplicationContext = parent
  • CPXAC.setConfigLocations(configLocations)
  • CPXAC.refresh()

Resource定位

ClassPathXmlApplicationContext context1 = new ClassPathXmlApplicationContext("classpath:spring-test.xml");
ClassPathResource("spring-test.xml", Launcher$AppClassLoader)

ClassPathXmlApplicationContext context2 = new ClassPathXmlApplicationContext("spring-test.xml");
ClassPathContextResource("spring-test.xml", Launcher$AppClassLoader)

FileSystemXmlApplicationContext context3 = new FileSystemXmlApplicationContext("spring-test.xml");
FileSystemResource("spring-test.xml") -> FileNotFoundException
需要"D:/spring-test.xml"
或者"classpath:spring-test.xml" -> ClassPathResource("spring-test.xml", Launcher$AppClassLoader)

ClassPathXmlApplicationContext context1 = new ClassPathXmlApplicationContext("classpath*:spring-test.xml");
UrlResource("file:/D:/work/code/jvtest/target/classes/spring-test.xml")
UrlResource("file:/D:/work/code/jvtest/target/test-classes/spring-test.xml")
多个

Document载入

InputStream inputStream = encodedResource.getResource().getInputStream()
InputSource inputSource = new InputSource(inputStream)
doLoadBeanDefinitions(inputSource, encodedResource.getResource());
// 载入 - 得到Document对象,用的org.w3c.dom
Document doc = doLoadDocument(inputSource, resource)

BeanDefinition注册

registerBeanDefinitions(doc, resource)

preProcessXml(root); // 自定义，默认空实现
parseBeanDefinitions(root, this.delegate)
postProcessXml(root); // 自定义，默认空实现

spring-003.jpg

parseBeanDefinitions(root, this.delegate)

• xml举例

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans 
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context.xsd">

    <context:property-placeholder location="classpath:envDev/config-dev.properties"/>

    <!--<context:annotation-config/>-->

    <context:component-scan base-package="com.fjh"/>

    <bean id="bean1" class="com.fjh.bean.Bean1" name="bean11" />
    
    <alias name="bean11" alias="bean111" />

    <import resource="classpath*:ds.xml"/>

</beans>

• beans
  • namespaceURI="http://www.springframework.org/schema/beans"
  • name="beans"
  • localName="beans"
• context:property-placeholder
  • namespaceURI="http://www.springframework.org/schema/context"
  • name="context:property-placeholder"
  • localName="property-placeholder"

beans:root
data:"\n\n    "
context:property-placeholder
data:"\n\n    "
data:<context:annotation-config/>
data:"\n\n    "
context:component-scan
...

parseDefaultElement - beans

• bean
  • 得到BeanDefinitionHolder
    • GenericBeanDefinition beanDefinition
      • beanClass
    • String beanName：id（不存在时用aliases首元素）
    • String[] aliases：name
  • 塞入DLBF.Map<beanName, BeanDefinition>
  • 塞入DLBF.Map<alias, beanName>
• beans
  • 递归调用doRegisterBeanDefinitions
• import
  • 递归加载xml
• alias
  • 塞入DLBF.Map<alias, name>

parseCustomElement

• 拿到节点的名空间，比如context
  • String namespaceUri = getNamespaceURI(ele)
• 找hander，怎么找呢
  • 加载所有META-INF/spring.handlers形成一个map
  • DefaultNamespaceHandlerResolver.resolve(namespaceUri)
• META-INF/spring.handlers

http\://www.springframework.org/schema/context=org.springframework.context.config.ContextNamespaceHandler
http\://www.springframework.org/schema/jee=org.springframework.ejb.config.JeeNamespaceHandler
http\://www.springframework.org/schema/lang=org.springframework.scripting.config.LangNamespaceHandler
http\://www.springframework.org/schema/task=org.springframework.scheduling.config.TaskNamespaceHandler
http\://www.springframework.org/schema/cache=org.springframework.cache.config.CacheNamespaceHandler

• ContextNamespaceHandler.init()
• 找到parser

registerBeanDefinitionParser("property-placeholder", new PropertyPlaceholderBeanDefinitionParser());
registerBeanDefinitionParser("property-override", new PropertyOverrideBeanDefinitionParser());
registerBeanDefinitionParser("annotation-config", new AnnotationConfigBeanDefinitionParser());
registerBeanDefinitionParser("component-scan", new ComponentScanBeanDefinitionParser());
registerBeanDefinitionParser("load-time-weaver", new LoadTimeWeaverBeanDefinitionParser());
registerBeanDefinitionParser("spring-configured", new SpringConfiguredBeanDefinitionParser());
registerBeanDefinitionParser("mbean-export", new MBeanExportBeanDefinitionParser());
registerBeanDefinitionParser("mbean-server", new MBeanServerBeanDefinitionParser());

AnnotationConfigBeanDefinitionParser

• 注册6个BeanPostProcessor，功能被component-scan包含

ComponentScanBeanDefinitionParser

• doScan(basePackages)得到Set<ScannedGenericBeanDefinition>
• 默认属性：lazyInit，initMethod，destroyMethod
• 注解属性：Lazy，Primary，DependsOn，Role，Description
• 塞到DLBF的map
• BeanPostProcessor的role=2
• 注册6个BeanPostProcessor

问答

classpath*:与classpath:区别

• resource1.jar的'com.test.rs'包有一个'jarAppContext.xml'文件

<bean id="processorImplA" class="com.test.spring.di.ProcessorImplA" />

• resource2.jar的 'com.test.rs'包也有一个'jarAppcontext.xml'文件

<bean id="processorImplB" class="com.test.spring.di.ProcessorImplB" />

// 可以把两个xml都加载进来
ApplicationContext context = new ClassPathXmlApplicationContext( "classpath*:com/test/rs/jarAppcontext.xml");
// 只会加载第一个xml
ApplicationContext context = new ClassPathXmlApplicationContext( "classpath:com/test/rs/jarAppcontext.xml");

base-package属性中的包在多个jar中出现

• 根据类加载器规则，同名类只会加载第一次

对于Bean依赖链，有没有做优化？

• 粗看下，并没有，不会特意优先加载没有需注入属性的bean