MVC运行过程
1. 客户端发送请求,首先进入DispatcherServlet
- 它是一个标准的servlet
- 第一次访问servlet(生命周期)是先走init()方法,再走service方法,最后是des
public class DispatcherServlet extends FrameworkServlet
public abstract class FrameworkServlet extends HttpServletBean implements ApplicationContextAware
在HttpServletBean有final的init方法,不能被重写,可以被继承
public final void init() throws ServletException {
if (logger.isDebugEnabled()) {
logger.debug("Initializing servlet '" + getServletName() + "'");
}
// Set bean properties from init parameters.
try {
PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
initBeanWrapper(bw);
bw.setPropertyValues(pvs, true);
}
catch (BeansException ex) {
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");
}
}
其中initWebApplicationContext方法特别重要
注:rootContext是spring容器,ConfigurableWebApplicationContext是springmvc容器。
如果实例化的是springmvc容器,那么把springmvc容器赋值给一个变量,该变量如果不是活动的,设置父容器为spring容器
protected WebApplicationContext initWebApplicationContext() {
WebApplicationContext rootContext =
WebApplicationContextUtils.getWebApplicationContext(getServletContext());
WebApplicationContext wac = null;
if (this.webApplicationContext != null) {
// A context instance was injected at construction time -> use it
wac = this.webApplicationContext;
if (wac instanceof ConfigurableWebApplicationContext) {
ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
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 -> set
// the root application context (if any; may be null) as the parent
cwac.setParent(rootContext);
}
configureAndRefreshWebApplicationContext(cwac);
}
}
}
if (wac == null) {
// No context instance was injected at construction time -> see if one
// has been registered in the servlet context. If one exists, it is assumed
// that the parent context (if any) has already been set and that the
// user has performed any initialization such as setting the context id
wac = findWebApplicationContext();
}
if (wac == null) {
// No context instance is defined for this servlet -> create a local one
wac = createWebApplicationContext(rootContext);
}
if (!this.refreshEventReceived) {
// Either the context is not a ConfigurableApplicationContext with refresh
// support or the context injected at construction time had already been
// refreshed -> trigger initial onRefresh manually here.
onRefresh(wac);
}
if (this.publishContext) {
// Publish the context as a servlet context attribute.
String attrName = getServletContextAttributeName();
getServletContext().setAttribute(attrName, wac);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Published WebApplicationContext of servlet '" + getServletName() +
"' as ServletContext attribute with name [" + attrName + "]");
}
}
return wac;
}
Spring 容器和 SpringMVC 容器的关系
从上述代码中可以看出来,Spring 容器和 SpringMVC 容器是父子容器
SpringMVC 容器中能够调用 Spring 容器的所有内容
结论:spring容器包含了springmvc容器,可以进行子类调用父类容器
到此,init方法主要是创建子容器,下来该进行service。
2.service
DispatcherServlet中没有service方法,存在doService方法,进入它的父类FrameworkServlet,有service方法。而service方法中获取请求方法,如果不区分大小写,获取方法名,放行请求到doService
- 对所有参数名进行循环遍历,把所有参数名转换成字符串,放入map集合中,进入doDispatch方法,进行转发