深入浅出Spring的IOC容器,对Spring的IOC容器源码进行深入理解

文章目录

  • 1.关于web.xml加载问题
    • 1.1.ServletContext 初始化
    • 1.2.ContextLoaderListener.contextInitialized(ServletContextEvent)
    • 1.3.ContextLoader.initWebApplicationContext
    • 1.4.servlet的初始化
    • 1.5.WebApplicationContext的主要实现类
      • 1.5.1.XmlWebApplicationContext
      • 1.5.2.AnnotationConfigWebApplicationContext
    • 1.6.总结
  • 2.DispatcherServlet
    • 2.1.整体继承图
    • 2.2.入口:DispatcherServlet.init()
    • 2.3.HttpServletBean.init()
    • 2.4.FrameworkServlet.initServletBean()

1.关于web.xml加载问题

1.1.ServletContext 初始化

1.Tomcat在进行启动的时候,会将context-param等相关参数全部初始化到ServletContext对象上
2.同时,会通知listener-class对应的类ContextLoaderListener(当然,也可以进行自定义)

web.xml 配置样例

<context-param>
   <param-name>name</param-name>
   <param-value>gaoxinfu</param-value>
</context-param>
<listener> 
   <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

1.2.ContextLoaderListener.contextInitialized(ServletContextEvent)

深入浅出Spring的IOC容器,对Spring的IOC容器源码进行深入理解_第1张图片

1.3.ContextLoader.initWebApplicationContext

/**
	 * Initialize Spring's web application context for the given servlet context,
	 * using the application context provided at construction time, or creating a new one
	 * according to the "{@link #CONTEXT_CLASS_PARAM contextClass}" and
	 * "{@link #CONFIG_LOCATION_PARAM contextConfigLocation}" context-params.
	 * @param servletContext current servlet context
	 * @return the new WebApplicationContext
	 * @see #ContextLoader(WebApplicationContext)
	 * @see #CONTEXT_CLASS_PARAM
	 * @see #CONFIG_LOCATION_PARAM
	 */
	public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {
     
		if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null) {
     
			throw new IllegalStateException(
					"Cannot initialize context because there is already a root application context present - " +
					"check whether you have multiple ContextLoader* definitions in your web.xml!");
		}

		Log logger = LogFactory.getLog(ContextLoader.class);
		servletContext.log("Initializing Spring root WebApplicationContext");
		if (logger.isInfoEnabled()) {
     
			logger.info("Root WebApplicationContext: initialization started");
		}
		long startTime = System.currentTimeMillis();

		try {
     
			// Store context in local instance variable, to guarantee that
			// it is available on ServletContext shutdown.
			if (this.context == null) {
     
				this.context = createWebApplicationContext(servletContext);
			}
			if (this.context instanceof ConfigurableWebApplicationContext) {
     
				ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) this.context;
				if (!cwac.isActive()) {
     
					// The context has not yet been refreshed -> provide services such as
					// setting the parent context, setting the application context id, etc
					if (cwac.getParent() == null) {
     
						// The context instance was injected without an explicit parent ->
						// determine parent for root web application context, if any.
						ApplicationContext parent = loadParentContext(servletContext);
						cwac.setParent(parent);
					}
					configureAndRefreshWebApplicationContext(cwac, servletContext);
				}
			}
			servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);

			ClassLoader ccl = Thread.currentThread().getContextClassLoader();
			if (ccl == ContextLoader.class.getClassLoader()) {
     
				currentContext = this.context;
			}
			else if (ccl != null) {
     
				currentContextPerThread.put(ccl, this.context);
			}

			if (logger.isDebugEnabled()) {
     
				logger.debug("Published root WebApplicationContext as ServletContext attribute with name [" +
						WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE + "]");
			}
			if (logger.isInfoEnabled()) {
     
				long elapsedTime = System.currentTimeMillis() - startTime;
				logger.info("Root WebApplicationContext: initialization completed in " + elapsedTime + " ms");
			}

			return this.context;
		}
		catch (RuntimeException ex) {
     
			logger.error("Context initialization failed", ex);
			servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex);
			throw ex;
		}
		catch (Error err) {
     
			logger.error("Context initialization failed", err);
			servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, err);
			throw err;
		}
	}

最终实现了下面的赋值
深入浅出Spring的IOC容器,对Spring的IOC容器源码进行深入理解_第2张图片
这里进行XMLWebApplicationContext的存储
深入浅出Spring的IOC容器,对Spring的IOC容器源码进行深入理解_第3张图片

1.4.servlet的初始化

上面listener的初始化parent context初始化完成之后,会进行初始化各个web.xml文件中的servlet
如下:servlet :DispatcherServlet的初始化,DispatcherServlet的初始化见下面章节

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
		 xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:javaee="http://java.sun.com/xml/ns/javaee"
		 xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
		 xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
		 version="2.4">
	<display-name>Gupao Web Application</display-name>

	<context-param>
		<param-name>name</param-name>
		<param-value>gaoxinfu</param-value>
	</context-param>
	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>
	
	<servlet>
		<servlet-name>myservlet</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
		<init-param>
			<param-name>contextConfigLocation</param-name>
			<param-value>application.properties</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>myservlet</servlet-name>
		<url-pattern>/*
	


1.5.WebApplicationContext的主要实现类

1.5.1.XmlWebApplicationContext

1.采用xml配置,则Spring将使用XmlWebApplicationContext启动Spring容器,即通过XML文件为Spring容器提供Bean的配置信息;

配置样例

	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>classpath:/config/applicationContext.xml</param-value>
	</context-param>
	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>

1.5.2.AnnotationConfigWebApplicationContext

如果使用@Configure的java类提供配置信息,则需要在xml中进行相关配置,
设置contextClass参数值为AnnotationConfigWebApplicationContext类,contextConfigLocation参数值则为使用了@Configure注解的类。

使用案例

@Configuration
@ServletComponentScan 
@ImportResource(locations = {
      "classpath:/config/applicationContext.xml" })
@SpringBootApplication
public class ThirdApplication {
     

	public static void main(String[] args) {
     
		System.setProperty("org.apache.cxf.stax.allowInsecureParser","1");
		 SpringApplication.run(ThirdApplication.class, args);
	}

深入浅出Spring的IOC容器,对Spring的IOC容器源码进行深入理解_第4张图片

1.6.总结

1.这里大家可以认为父parent context:WebApplicationContext的初始化;

首先大家,去看Spring的源码入口,第一个就是DispatcherServlet

2.DispatcherServlet

2.1.整体继承图

深入浅出Spring的IOC容器,对Spring的IOC容器源码进行深入理解_第5张图片

2.2.入口:DispatcherServlet.init()

可以看到入口在HttpServletBean.init()中

2.3.HttpServletBean.init()

@Override
	public final void init() throws ServletException {
     
		if (logger.isDebugEnabled()) {
     
			logger.debug("Initializing servlet '" + getServletName() + "'");
		}

		// Set bean properties from init parameters.
		PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
		if (!pvs.isEmpty()) {
     
			try {
     
				//定位资源
				BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
				//加载配置信息
				ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
				bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
				initBeanWrapper(bw);
				bw.setPropertyValues(pvs, true);
			}
			catch (BeansException ex) {
     
				if (logger.isErrorEnabled()) {
     
					logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
				}
				throw ex;
			}
		}

		// Let subclasses do whatever initialization they like.
		initServletBean();

		if (logger.isDebugEnabled()) {
     
			logger.debug("Servlet '" + getServletName() + "' configured successfully");
		}
	}

深入浅出Spring的IOC容器,对Spring的IOC容器源码进行深入理解_第6张图片

2.4.FrameworkServlet.initServletBean()

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