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Introduction to Spring MVC

Spring MVC is a lightweight Web framework based on MVC architecture pattern, which aims to modularize Web development and decouple the overall architecture.

Spring MVC has the following advantages:

As part of the Spring framework, have the advantages of Spring (IOC,AOP, etc.)

Support flexible URL-to-page controller mapping

Provide flexible data validation, formatting, and data binding mechanisms

Support RESTful style

Spring MVC request process

The overall request flow of the Spring MVC framework is as follows:

Several functional components of Spring MVC are involved in the figure above:

Front-end controller (DispatcherServlet): receives the user request and returns the result of the request. Its function is equivalent to a transponder or central processing unit, which controls the whole execution flow and schedules each component to reduce the coupling between components.

Processor mapper (HandlerMapping): according to the URL requested by the user, find the corresponding processor Handler through annotations or XML configuration

Processor adaptation (HandlerAdapter): according to the Handler found by the mapper, the method in the processor is called.

Processor (Handler): specific logic for request processing, returning data and view information

View parser (View Resolver): parses a specific view and parses the logical view name into a real view View through the View information in the ModelAndView object

Detailed description of the specific steps of the request process:

1: when a user initiates a request, the request is intercepted by the front-end controller (DispatcherServlet)

2: the front-end controller (DispatcherServlet) requests the processor mapper (HandlerMapping) to find the Handler

3: the processor mapper (HandlerMapping) finds the appropriate Handler according to the configuration (can be more annotated or XML configured), and may contain multiple Interceptor interceptors, which are returned to the front-end controller

4: the front-end controller (DispatcherServlet) requests the processor adapter (HandlerAdapter) to execute the corresponding Handler

5: the adapter is executed by the corresponding Handler processor

6: after the execution of the Handler processor, the ModelAndView object is returned to the processor adapter

7: the processor adapter accepts the result returned by the Handler processor and returns the result to the front-end controller (DispatcherServlet)

8: the front controller (DispatcherServlet) receives the data and view information returned by the processor adapter, requests the view parser, and parses the corresponding view

9: the view parser returns the corresponding view results matched by the View information to the front-end controller

10: the front-end controller receives the specific view, renders the view, populates the Model data into the View view, and generates the final view

11: the front-end controller returns the result to the user

Build demo from scratch

Create a project:

Create a new dynamic Web project under Eclipse

Default directory structure of the project:

Add jar package dependencies

Import the corresponding jar package under the WebContent > WEB-INF > lib folder, where the core jar package is spring-webmvc-5.0.0.RELEASE.jar, and the others are mainly spring for managing context and beande packages, jstl tag libraries, and a log package for printing logs:

Configure the front-end controller in web.xml

The front-end controller is equivalent to the proprietary servlet of Spring MVC, which is used to intercept all eligible requests and leave them to the framework for subsequent processing.

SpringMvcNext org.springframework.web.servlet.DispatcherServlet contextConfigLocation classpath:applicationContext.xml springMvcNext /

Add controller Controller and view View

Add the package com.sl.controller under the Src directory, and add the controller code as follows:

Package com.sl.controller;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.servlet.ModelAndView;@Controllerpublic class HelloWorldController {@ RequestMapping ("/ index") / / processes all requests starting with / index in the URL path: including / index/* and / index.html public ModelAndView helloWorld () {String message = "Hello Spring MVC"; return new ModelAndView ("index", "message", message);}}

Add the view file index.jsp to WEB-INF/view

Spring MVC ${message}

Running result:

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