ssm framework day 8: Spring MVC
1. Basic concepts of spring MVC
1. Strictly follow the framework of web layer designed by mvc design model
2. It is a follow-up product of spring framework
Spring MVC is a request driven lightweight web framework based on Java to implement MVC design model. It is a follow-up product of Spring FrameWork and has been integrated into Spring Web Flow. The Spring FrameWork provides a fully functional MVC module for building web applications. Using the spring pluggable MVC architecture, when using spring for web development, you can choose to use spring MVC framework or integrate other MVC development frameworks, such as struts 1 (generally not used now), struts 2, etc.
Spring MVC has become one of the most popular MVC frameworks, and with spring 3 0, comprehensively surpassing struts 2 and becoming the best MVC framework.
Through a set of annotations, it makes a simple Java class a controller for processing requests without implementing any interface. meanwhile
It also supports RESTful programming style requests
2. Getting started with spring MVC
2.1 environment construction
1. Import dependency
<dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.11</version> <scope>test</scope> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>5.0.2.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-web</artifactId> <version>5.0.2.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>5.0.2.RELEASE</version> </dependency> <dependency> <groupId>javax.servlet</groupId> <artifactId>servlet-api</artifactId> <version>2.5</version> <scope>provided</scope> </dependency> <dependency> <groupId>javax.servlet</groupId> <artifactId>jsp-api</artifactId> <version>2.0</version> <scope>provided</scope> </dependency>
2.web.xml configuration
<!--to configure Springmvc DispatcherServlet(Springmvc Core front end controller)--> <servlet> <servlet-name>dispatcherServlet</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <!--Is let spring The front-end controller is loaded when it is created springmvc.xml Create various profiles controller object--> <init-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:springmvc.xml</param-value> </init-param> <!--Can let Servlet Created when the server starts--> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>dispatcherServlet</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping>
3. Spring MVC configuration file
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns:mvc="http://www.springframework.org/schema/mvc" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd"> <!--Configure package scanning Create all Controller object --> <context:component-scan base-package="com.bianyiit.web"></context:component-scan> <!--Configure view parser--> <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <!--Specifies the prefix for logical to physical view conversion --> <property name="prefix" value="/WEB-INF/views/"></property> <!--Specifies the suffix for logical to physical view conversion --> <property name="suffix" value=".jsp"></property> </bean> <!--Automatic loading SpringMVC Two other component processor mapper processor adapters --> <mvc:annotation-driven></mvc:annotation-driven> </beans>
4.controller class and jsp page
<%-- Created by IntelliJ IDEA. User: zengl Date: 2019/10/25 Time: 11:21 To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %> <html> <head> <title>springmvc introduction</title> </head> <body> <a href="${pageContext.request.contextPath}/user/helloWorld">springmvc Entry test</a> </body> </html>
package com.bianyiit.web; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; @Controller /** Defines the path prefix for method access in the class */ @RequestMapping("/user") public class UserController { /** * Complete the mapping relationship between request path and method * * A module uses a UserController */ //(path ={"/helloWorld"}, // method ={RequestMethod.GET,RequestMethod.POST}, //Request mode for qualified method access // params={"username"}, //Qualified parameter. If the request parameter name is specified, the request must carry the parameter // headers = {"Accept"}//Qualified request header @RequestMapping("/hello") public String helloWorld(){ System.out.println("UserController Medium helloWorld Yes"); return "hello"; } }
Spring MVC projects: (they are created and loaded when the project starts)
1. When the project is started (as soon as it is started), web.xml will be loaded and the front-end controller configured in the XML file will be created.
2. The configuration file of spring MVC will be loaded
3. All controller layer objects will be created
4. The three components of spring MVC will be created
Request process:
The user sends a request in the browser, which is received by the dispatchServlet, then distributes the request, finds the corresponding mapping path of the controller layer, processes the request, returns the logical view, converts it into a physical view through the configured view parser, returns it to the front-end jsp page, and then sends the data to be displayed to the browser on the jsp page.
3. Operating principle of spring MVC
As shown in the figure:
Personal understanding of operation process:
1. The user sends a request on the front page
2. The request first passes through the front-end controller (DispatchServlet), which will control the global
3. The front-end controller will find the processor mapper. The processor will take the front-end path to the corresponding controller layer, find the corresponding mapping, compare, find the processor, and then return to the DIspatchServlet
4.DispatchServlet will find the processor adapter, find the corresponding processor, and return the model and view to dispatchservlet
5.DispatchServlet will go to the view parser to convert the logical view into a physical view, and then return to DispatchServlet
6.DispatchServlet returns the corresponding data to the browser through the front-end view
4. Receipt of request parameters
The code is as follows:
package com.bianyiit.web; import com.bianyiit.domian.User; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; @Controller @RequestMapping("/param") public class ParamController { /** * Controller Methods can accept Servlet related API s * @param request * @param response * @return */ @RequestMapping("/hello") public String hello(HttpServletRequest request, HttpServletResponse response){ //1. Get request parameters System.out.println(request.getParameter("username")); System.out.println(request.getParameter("password")); return "hello"; } @RequestMapping("/hello1") public String hello1(String username,String password){ //1. Get request parameters System.out.println(username+ " :: " + password); return "hello"; } @RequestMapping("/hello2") public String hello2(User user){ //1. Get request parameters System.out.println(user.getUsername()+ " :: " + user.getPassword()); return "hello"; } }
Note: the parameter name (name) requested by the front end should be consistent with the attribute name of the back end (one-to-one correspondence)
Today's learning experience: learning is not only a part of life, but also a very important part. The above is only personal understanding. If there is any improper understanding, I hope you can correct me. Thank you! Last sentence: I hope you become the person you want to be!