上一节介绍了Spring创建过程中的两个重要的接口，那么它们在创建Bean的过程中起到了什么作用呢？接下来请看：

Spring有三种方式寻找 xml 配置文件，根据 xml 文件内容来构建 ApplicationContext，分别为ClassPathXmlApplicationContext，FileSystemXmlApplicationContext ，AnnotationConfigApplicationContext 和 AnnotationConfigServletWebApplicationContext。

动手创建Bean

创建接口实现类

public class beanImpl implements bean{@Overridepublic void print() {System.out.println("bean");}
}

创建xml文件

<?xml version="1.0" encoding="UTF-8" ?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns="http://www.springframework.org/schema/beans"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd" default-autowire="byName"><bean id="bean" class="com.beanImpl"/>
</beans>

运行

public class A01Application {public static void main(String[] args) {ApplicationContext context = new ClassPathXmlApplicationContext("classpath:bean.xml");context.getBean(bean.class).print();}
}D:\jdk8\bin\java.exe "-javaagent:F:\idea\IntelliJ IDEA 
22:49:09.159 [main] DEBUG org.springframework.context.s
22:49:09.261 [main] DEBUG org.springframework.beans.fac
22:49:09.282 [main] DEBUG org.springframework.beans.fac
bean进程已结束,退出代码0

那么，读取xml的时候发生了什么事呢

内部实现

public static void main(String[] args) {DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();XmlBeanDefinitionReader xmlBeanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);xmlBeanDefinitionReader.loadBeanDefinitions(new ClassPathResource("bean.xml"));for (String name : beanFactory.getBeanDefinitionNames()){System.out.println(name);}}D:\jdk8\bin\java.exe "-javaagent:F:\idea\In
23:05:26.396 [main] DEBUG org.springframewo
bean进程已结束,退出代码0

注解创建Bean

public class A03Application {public static void main(String[] args) {AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(beanConfig.class);context.getBean(bean.class).print();for (String name : context.getBeanDefinitionNames()){System.out.println(name);}}
}bean
org.springframework.context.annotation.internalConfigurationAnnotationProcessor
org.springframework.context.annotation.internalAutowiredAnnotationProcessor
org.springframework.context.annotation.internalCommonAnnotationProcessor
org.springframework.context.event.internalEventListenerProcessor
org.springframework.context.event.internalEventListenerFactory
beanConfig
bean
与目标 VM 断开连接, 地址为: ''127.0.0.1:64717'，传输: '套接字''进程已结束,退出代码0

注解创建Bean会把配置类也作为Bean注入进来，同时还会添加5个后处理器，来进行对beanConfig的解析处理。

支持WEB的注解创建Bean

创建支持web的配置类

@Configuration
public class WebConfig {//创建Servlet的web服务器@Beanpublic ServletWebServerFactory servletWebServerFactory(){return new TomcatServletWebServerFactory();}//创建前处理器，用来接收各种请求@Beanpublic DispatcherServlet dispatcherServlet(){return new DispatcherServlet();}//将dispatcherServlet注册在web服务器上@Beanpublic DispatcherServletRegistrationBean dispatcherServletRegistrationBean(DispatcherServlet dispatcherServlet){return new DispatcherServletRegistrationBean(dispatcherServlet,"/");}//Controller控制器@Bean("/bean")public Controller controller(){return new Controller() {@Overridepublic ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {System.out.println("bean");return null;}};}
}

再运行一下主类吧

public class A04Application {public static void main(String[] args) {AnnotationConfigServletWebServerApplicationContext context = new AnnotationConfigServletWebServerApplicationContext(WebConfig.class);for (String name : context.getBeanDefinitionNames()){System.out.println(name);}}
}org.springframework.context.annotation.internalConfigurationAnnotationProcessor
org.springframework.context.annotation.internalAutowiredAnnotationProcessor
org.springframework.context.annotation.internalCommonAnnotationProcessor
org.springframework.context.event.internalEventListenerProcessor
org.springframework.context.event.internalEventListenerFactory
webConfig
servletWebServerFactory
dispatcherServlet
dispatcherServletRegistrationBean
/bean

 这样就能发现创建了所有的Bean，而且，还可以通过内置服务器运行接收请求。

                                                                                                                             to be continue······