怀玉:点个关注,必回关
一、什么是MVC
MVC英文是Model View
Controller,是模型(model)-视图(view)-控制器(controller)的缩写,一种软件设计规范。本质上也是一种解耦
·Model
(模型)是应用程序中用于处理应用程序数据逻辑的部分。通常模型对象负责在数据库中存取数据。
·View
(视图)是应用程序中处理数据显示的部分。通常视图是依据模型数据创建的。
·Controller
(控制器)是应用程序中处理用户交互的部分。通常控制器负责从视图读取数据,控制用户输入,并向模型发送数据。
二、什么是spring mvc
简单而言,Spring MVC是Spring在Spring Container Core和AOP等技术基础上,遵循上述Web
MVC的规范推出的web开发框架,目的是为了简化Java栈的web开发
1、spring web mvc 请求流程
首先用户发送请求——>DispatcherServlet
,前端控制器收到请求后自己不进行处理,而是委托给其他的解析器进行 处理,作为统一访问点,进行全局的流程控制;
DispatcherServlet——>HandlerMapping
, HandlerMapping
将会把请求映射为 HandlerExecutionChain
对象(包含一 个Handler 处理器(页面控制器)对象、多个HandlerInterceptor
拦截器)对象,通过这种策略模式,很容易添加新 的映射策略;
DispatcherServlet——>HandlerAdapter
,HandlerAdapter
将会把处理器包装为适配器,从而支持多种类型的处理器, 即适配器设计模式的应用,从而很容易支持很多类型的处理器;
HandlerAdapter——>处理器功能处理方法的调用,HandlerAdapter
将会根据适配的结果调用真正的处理器的功能处 理方法,完成功能处理;并返回一个ModelAndView
对象(包含模型数据、逻辑视图名);
ModelAndView 的逻辑视图名——> ViewResolver
,ViewResolver
将把逻辑视图名解析为具体的View
,通过这种策 略模式,很容易更换其他视图技术;
View——>渲染,View
会根据传进来的Model 模型数据进行渲染,此处的Model
实际是一个Map
数据结构,因此 很容易支持其他视图技术;
返回控制权给DispatcherServlet,由DispatcherServlet
返回响应给用户,到此一个流程结束
三、spring mvc 案例
1、项目结构:
2、maven
包引入
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>tech-pdai-spring-demos</artifactId>
<groupId>tech.pdai</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>011-spring-framework-demo-springmvc</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging>
<properties>
<maven.compiler.source>8</maven.compiler.source>
<maven.compiler.target>8</maven.compiler.target>
<spring.version>5.3.9</spring.version>
<servlet.version>4.0.1</servlet.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>${servlet.version}</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>taglibs</groupId>
<artifactId>standard</artifactId>
<version>1.1.2</version>
</dependency>
</dependencies>
</project>
3、业务代码
User实体
package tech.pdai.springframework.springmvc.entity;
/**
* @author pdai
*/
public class User {
/**
* user's name.
*/
private String name;
/**
* user's age.
*/
private int age;
/**
* init.
*
* @param name name
* @param age age
*/
public User(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
Dao
package tech.pdai.springframework.springmvc.dao;
import org.springframework.stereotype.Repository;
import tech.pdai.springframework.springmvc.entity.User;
import java.util.Collections;
import java.util.List;
/**
* @author pdai
*/
@Repository
public class UserDaoImpl {
/**
* mocked to find user list.
*
* @return user list
*/
public List<User> findUserList() {
return Collections.singletonList(new User("pdai", 18));
}
}
service
package tech.pdai.springframework.springmvc.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import tech.pdai.springframework.springmvc.dao.UserDaoImpl;
import tech.pdai.springframework.springmvc.entity.User;
import java.util.List;
/**
* @author pdai
*/
@Service
public class UserServiceImpl {
/**
* user dao impl.
*/
@Autowired
private UserDaoImpl userDao;
/**
* find user list.
*
* @return user list
*/
public List<User> findUserList() {
return userDao.findUserList();
}
}
Controller
package tech.pdai.springframework.springmvc.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;
import tech.pdai.springframework.springmvc.service.UserServiceImpl;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Date;
/**
* User Controller.
*
* @author pdai
*/
@Controller
public class UserController {
@Autowired
private UserServiceImpl userService;
/**
* find user list.
*
* @param request request
* @param response response
* @return model and view
*/
@RequestMapping("/user")
public ModelAndView list(HttpServletRequest request, HttpServletResponse response) {
ModelAndView modelAndView = new ModelAndView();
modelAndView.addObject("dateTime", new Date());
modelAndView.addObject("userList", userService.findUserList());
modelAndView.setViewName("userList"); // views目录下userList.jsp
return modelAndView;
}
}
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
version="3.1">
<display-name>SpringFramework - SpringMVC Demo @pdai</display-name>
<servlet>
<servlet-name>springmvc-demo</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<!-- 通过初始化参数指定SpringMVC配置文件的位置和名称 -->
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:springmvc.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>springmvc-demo</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<filter>
<filter-name>encodingFilter</filter-name>
<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
<init-param>
<param-name>forceEncoding</param-name>
<param-value>true</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>encodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>
springmvc.xml
<?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"
xmlns:jpa="http://www.springframework.org/schema/data/jpa"
xmlns:tx="http://www.springframework.org/schema/tx"
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
http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd">
<!-- 扫描注解 -->
<context:component-scan base-package="tech.pdai.springframework.springmvc"/>
<!-- 静态资源处理 -->
<mvc:default-servlet-handler/>
<!-- 开启注解 -->
<mvc:annotation-driven/>
<!-- 视图解析器 -->
<bean id="jspViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
<property name="prefix" value="/WEB-INF/views/"/>
<property name="suffix" value=".jsp"/>
</bean>
</beans>
userlist.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>User List</title>
<!-- Bootstrap -->
<link rel="stylesheet" href="//cdn.bootcss.com/bootstrap/3.3.5/css/bootstrap.min.css">
</head>
<body>
<div class="container">
<c:if test="${!empty userList}">
<table class="table table-bordered table-striped">
<tr>
<th>Name</th>
<th>Age</th>
</tr>
<c:forEach items="${userList}" var="user">
<tr>
<td>${user.name}</td>
<td>${user.age}</td>
</tr>
</c:forEach>
</table>
</c:if>
</div>
</body>
</html>