1.什么是MVC
-
MVC : 模型、视图、控制器 , 是一种软件设计规范,说明不是设计模式;
-
本质:将业务逻辑 , 数据 , 显示 分离的方式来编写代码; 前后端分离;
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Model:数据模型,提供要展示的数据,一般我们都会把这两个分离开来 , 数据Dao,服务层Service。
-
View :负责进行数据的渲染和展示;客户端想要看到的东西
-
Controller:接收用户请求,交给Model处理,从Model更新后的数据或者结果,返回给前端。调度员
面向接口编程
最典型的案例就是:JSP:View+Servlet:Controller+JavaBean:Model;
Model1
在早期的Web开发中,就是用的Model1模式
只有两层:视图层和模型层;
优点:架构简单,适合小型项目开发;
缺点:JSP职责不单一 , 承受它不该承受的压力,不便于维护;
Model2
将项目分为三个模块:M:模型 V:视图 C:控制器
职责分析:
controller:
- 取得表单的数据
- 调用业务的逻辑方法
- 转向指定的页面
Model:
- Dao:操作数据库
- Service:业务逻辑
- 保存数据的更新状态
View:
- 显示页面
Model2优化了Model1时代的缺点,让所有层职责更加分明;降低了维护难度,
2.SpringMVC
SpringMVC 是 Spring的一部分,是基于Java实现的MVC的轻量级Web框架
实例
我们利用Maven创建一个web项目;
1.创建依赖,解决资源导出问题
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<!--SpringMVC及Spring系列包-->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>4.3.24.RELEASE</version>
</dependency>
<!--Servlet核心-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
</dependency>
<!--JSTL-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
</dependencies>
<build>
<!--解决资源导出问题-->
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
</resources>
注册SpringMVC核心Servlet
<?xml version="1.0" encoding="UTF-8"?>
<web-app
version="3.0"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<servlet>
<servlet-name>SpringMVC</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<!--关联SpringMVC配置文件-->
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:springmvc-servlet.xml</param-value>
</init-param>
<!--这个东西要和服务器一起启动;
load-on-startup。启动级别,数字越小级别越高
-->
<load-on-startup>1</load-on-startup>
</servlet>
<!--所有请求都会经过这个DispatcherServlet请求分发器-->
<!--
/和/*的区别:
< url-pattern > / </ url-pattern > 不会匹配到.jsp, 只针对我们编写的请求;
即:.jsp不会进入spring的 DispatcherServlet类 。
< url-pattern > /* </ url-pattern > 会匹配*.jsp,
会出现返回jsp视图时再次进入spring的DispatcherServlet 类,导致找不到对应的controller所以报404错。
-->
<servlet-mapping>
<servlet-name>SpringMVC</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
注意:映射路径位 / (不要用/*,会404)
编写SpringMVC的配置文件
- 让IOC的注解生效
- 静态资源过滤 :HTML . JS . CSS . 图片 , 视频 …
- MVC的注解驱动 :
- 配置视图解析器
<?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:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
https://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/mvc
https://www.springframework.org/schema/mvc/spring-mvc.xsd">
<!--扫描指定包下的注解,让指定的类能够被IOC容器管理-->
<context:component-scan base-package="com.wang.controller"/>
<!--静态资源过滤-->
<mvc:default-servlet-handler/>
<!--支持MVC注解驱动-->
<mvc:annotation-driven/>
<!--视图解析器
作用;方便统一管理-->
<bean id="InternalResourceViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/jsp/"/>
<property name="suffix" value=".jsp"/>
</bean>
</beans>
编写Controller类
- 需要给类加注解 :@Controller , 可以让IOC容器管理 , 等价于Bean
- 请求映射的路径 :@RequestMapping (“路径”),如果类上有就先写类的,在写方法的;
- Model :模型传递参数
- return “hello”; 它会去视图解析中拼接前缀和后缀来找到对应的视图
@Controller
@RequestMapping("/hello")
public class HelloWorldController {
//请求映射("路径")
@RequestMapping("/hello")
public String hi(Model model){
model.addAttribute("msg","Hello,SpringMVC");
System.out.println("进入HELLO");
return "hello"; //WEB-INF/jsp/hello.jsp
}
}
视图层
- 注意视图的位置,要和视图解析器对应 web-inf / jsp , 为什么需要在web-inf路径下 , 因为这个路径下的东西用户无法直接访问 , 更加安全;
- 可以通过EL表示取出Model中存放的值,或者对象
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>SpringMVC</title>
</head>
<body>
${msg}
</body>
</html>
启动Tomcat进行测试,测试结果
Controller配置
使用SpringMVC必须配置三大文件:
处理器映射器,处理器适配器 (一般加上)
配置web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="WebApp_ID" version="3.0">
<!--注册Servlet中心分发器-->
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:springmvc-servlet.xml</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
编写springmvc-servlet.xml文件
<?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:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
https://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/mvc
https://www.springframework.org/schema/mvc/spring-mvc.xsd">
<!--自动扫描包-->
<context:component-scan base-package="com.wang.controller"/>
<bean id="InternalResourceViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<!--前缀-->
<property name="prefix" value="/WEB-INF/jsp/"/>
<!--后缀-->
<property name="suffix" value=".jsp"/>
</bean>
</beans>
编写controller类
@Controller
public class HelloController {
@RequestMapping("/h1")
public ModelAndView hello(HttpServletRequest req, HttpServletResponse resp){
ModelAndView mv = new ModelAndView();
mv.addObject("msg","大圣归来");
mv.setViewName("hello");
return mv;
}
@RequestMapping("/h2")
public ModelAndView hello2(HttpServletRequest req, HttpServletResponse resp){
ModelAndView mv = new ModelAndView();
mv.addObject("msg","猴哥,师傅不见了");
mv.setViewName("hello");
return mv;
}
}
@Controller
@RequestMapping("/admin")
public class AnnoController {
@RequestMapping("/anno")
public ModelAndView hello(HttpServletRequest req, HttpServletResponse resp){
ModelAndView mv = new ModelAndView();
mv.addObject("msg","哪吒闹海");
mv.setViewName("hello");
return mv;
}
@RequestMapping("/anno2")
public ModelAndView hello2(HttpServletRequest req, HttpServletResponse resp){
ModelAndView mv = new ModelAndView();
mv.addObject("msg","中国梦!");
mv.setViewName("hello");
return mv;
}
}
@org.springframework.stereotype.Controller
public class ThreeController implements Controller {
@RequestMapping("hand")
@Override
public ModelAndView handleRequest(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws Exception {
ModelAndView mv = new ModelAndView();
mv.addObject("msg","你好");
mv.setViewName("hello");
return mv;
}
}
视图层,接收会话
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
${msg}
</body>
</html>
测试结果: