Spring MVC 关键点 理解

学习 Spring MVC 源码 理解

1.工作流程了解

跟踪了一下dispatch servlet的源码，结合这张图以及这篇博客分析了一下

http://www.cnblogs.com/davidwang456/p/4096530.html



了解了 springMVC的整个工作流程

2.参数传递

还有一点就是记不住 关于springMVC 的返回值类型，String，ModelAndView；

跟踪了一下源码

2.1 dispatch servlet类的 doDispatch 方法里面，调用适配器进行处理后，一定会返回一个 modelandview，跟踪进去

mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

2.2 org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter这个类里面进行handle处理，即返回这个modelandview，继续跟踪；

return invokeHandlerMethod(request, response, handler);

2.3 org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter这个类里面最关键的地方，创建了一个 modelandview，也就是说，返回的东西在这里一定会被包装，同样，modelMap也会被 塞进去参数

protected ModelAndView invokeHandlerMethod(HttpServletRequest request, HttpServletResponse response, Object handler)
throws Exception {

ServletHandlerMethodResolver methodResolver = getMethodResolver(handler);
Method handlerMethod = methodResolver.resolveHandlerMethod(request);
ServletHandlerMethodInvoker methodInvoker = new ServletHandlerMethodInvoker(methodResolver);
ServletWebRequest webRequest = new ServletWebRequest(request, response);
ExtendedModelMap implicitModel = new BindingAwareModelMap();

Object result = methodInvoker.invokeHandlerMethod(handlerMethod, handler, webRequest, implicitModel);
ModelAndView mav =
methodInvoker.getModelAndView(handlerMethod, handler.getClass(), result, implicitModel, webRequest);
methodInvoker.updateModelAttributes(handler, (mav != null ? mav.getModel() : null), implicitModel, webRequest);
return mav;
}

2.4换句话说，返回前台的参数都在 modelMap 里面，返回的 ModelAndView一定要携带modelMap，所以就有以下三种方式来传递参数回去,恩这样就理解了吧

@RequestMapping("/testIn")
public String testIn( ModelMap model,@RequestParam(value = "templateId") Long templateId){
System.out.println("---------------testIn");
model.addAttribute("para01","para01");
return "test";
}

@RequestMapping("/testIn2")
public ModelAndView testIn2(@RequestParam(value = "templateId") Long templateId){
System.out.println("---------------testIn2");
ModelAndView mv = new ModelAndView("/test");
mv.addObject("para01","para002");
return mv;
}
@RequestMapping("/testIn3")
public ModelAndView testIn3(@RequestParam(value = "templateId") Long templateId){
System.out.println("---------------testIn3");
ModelMap map = new ModelMap();
map.put("para01","para003");
ModelAndView mv = new ModelAndView("/test");
mv.addObject(map);
return mv;
}