Spring中MVC框架的底層實現

Spring中的MVC

Spring MVC的流程

Spring的Sample這裡就不講了，大家自己上網google

Spring 在Web環境下的啟動

按照javaEE標准，Web應用啟動web.xml，之後的啟動root是ServletContextListener。

(問題： ContextListener如何啟動？ 隨著web容器啟動而啟動？是單線程的？線程安全的？)

ContextListener是隨著Tomcat的啟動而啟動，並且只啟動這一次，為整個WebContext的啟動做准備。

Spring在Web環境下啟動的監聽器是：

1. public class ContextLoaderListener extends ContextLoader implements ServletContextListener {
2. /**
3. * Initialize the root web application context.
4. */
5. public void contextInitialized(ServletContextEvent event) {
6. this.contextLoader = createContextLoader();
7. if (this.contextLoader == null) {
8. this.contextLoader = this;
9. }
10. this.contextLoader.initWebApplicationContext(event.getServletContext());
11. }

其中WebApplication的上下文在ContextLoader中初期化

1. /**
2. * Initialize Spring's web application context for the given servlet context,
3. * using the application context provided at construction time, or creating a new one
4. * according to the "{@link #CONTEXT_CLASS_PARAM contextClass}" and
5. * "{@link #CONFIG_LOCATION_PARAM contextConfigLocation}" context-params.
6. * @param servletContext current servlet context
7. * @return the new WebApplicationContext
8. * @see #ContextLoader(WebApplicationContext)
9. * @see #CONTEXT_CLASS_PARAM
10. * @see #CONFIG_LOCATION_PARAM
11. */
12. public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {
13. try {
14. // Store context in local instance variable, to guarantee that
15. // it is available on ServletContext shutdown.
16. if (this.context == null) {
17. this.context = createWebApplicationContext(servletContext);
18. }

最後的啟動委托給XmlWebApplicationContext

這個類中使用了大量的模板設計模式！！

最終的容器啟動和我們編程式啟動Spring類同

1. /**
2. * Loads the bean definitions via an XmlBeanDefinitionReader.
3. * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
4. * @see #initBeanDefinitionReader
5. * @see #loadBeanDefinitions
6. */
7. @Override
8. protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
9. // Create a new XmlBeanDefinitionReader for the given BeanFactory.
10. XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
12. // Configure the bean definition reader with this context's
13. // resource loading environment.
14. beanDefinitionReader.setEnvironment(this.getEnvironment());
15. beanDefinitionReader.setResourceLoader(this);
16. beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
18. // Allow a subclass to provide custom initialization of the reader,
19. // then proceed with actually loading the bean definitions.
20. initBeanDefinitionReader(beanDefinitionReader);
21. loadBeanDefinitions(beanDefinitionReader);
22. }