What is the Spring MVC life cycle?

## Today is the first time to contact Spring mvc. First, let’s start with Spring mvc its life cycle to understand it.

Recommended course:

Java Tutorial.

First, the browser will send a request, and our project receives the request through a servlet named dispatcherServlet in spring.

This Servlet receives After the request, it will be verified whether it is the first time to load this Servlet. If this is the first time to load this Servlet, dispatcherServlet will do some initialization operations at this time.

dispatcherServlet will initialize HandlerMapping (note: it handles the mapping of client requests to each Controller processor)

dispatcherServlet will initialize HandlerAdapter (note: HandlerMapping will be called based on it) Methods that need to be executed in the Controller)

dispatcherServlet will initialize handlerExceptionResolver (Note: In the spring mvc processing process, if an exception is thrown, it will be handed over to it for exception handling)

dispatcherServlet will initialize ViewResolver (Note: HandlerAdapter will eventually wrap the return value from the call in Controller into

ModelAndView. ViewResolver will check the view. If the view is a string, it is responsible for processing this character. Concatenate and return a real View if If the view is a real View, it will not be handed over to it for processing)

After the above is initialized, the dispatcherServlet will start querying one or more handlerMaprrings to map the request to a controller object

If a controller object is not found at this time, an exception will be thrown.

If a controller object is found, the request will be processed by the preHandle of an interceptor chain and matched to the controller through the handlerAdapter. The specific method of the object

Then this method will process the request according to our business logic. After completing the processing of the business logic, the controller will get a ModelAndView object (Note: vie

in this class

This property is of type Object, it can be a view name or an actual View) After getting this ModelAndView, spring will determine whether the viewName of ModelAndView is of type String

If it is a String type, directly call the getView method of ModelAndView, then find the corresponding page and return the information to the DispatcherServlet

If it is not a string type, then it will find the name in the ViewResolver based on the viewName and then determine its correspondence. The page then returns the page to dispatcherserlvet

Finally, dispatcherSerlvet will return the obtained page to the browser.

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