49.SpringMVC简单整理

SpringMVC 本质也是解耦

先提前插一嘴
这里用到的是简单的maven项目：
在添加web应用时报错
Artifacts Web facet resources 爆红
参考：https://blog.csdn.net/weixin_43739266/article/details/122133398 添加web依赖

要为项目添加web项目依赖否则无法tomcat访问

---

为了介绍MVC我打算直接用一个例子来看：、

首先位于WEB-INF下文件夹jsp建一个hello.jsp 用于显示

没用springboot之前我们需要手动编写xml文件：

来看几步死的：

1.web.xml的配置 需要更改的就是 classpath:你的.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_4_0.xsd"
         version="4.0">
 
 
    <!--1.注册DispatcherServlet-->
    <servlet>
        <servlet-name>springmvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <!--关联一个springmvc的配置文件:【servlet-name】-servlet.xml-->
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:springmvc_servlet.xml</param-value>
        </init-param>
        <!--启动级别-1-->
        <load-on-startup>1</load-on-startup>
    </servlet>
 
    <!--/ 匹配所有的请求；（不包括.jsp）-->
    <!--/* 匹配所有的请求；（包括.jsp）-->
    <servlet-mapping>
        <servlet-name>springmvc</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
<!--spring提供解决乱码问题-->
    <filter>
        <filter-name>encoding</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>
    </filter>
    <filter-mapping>
        <filter-name>encoding</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

2.你对应路径下的 Springmvc.xml

classpath 下即resource下创建的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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd">
 
    <bean class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping"/>
    <bean class="org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter"/>
 
    <!--视图解析器:DispatcherServlet给他的ModelAndView-->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" id="InternalResourceViewResolver">
        <!--前缀-->
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <!--后缀-->
        <property name="suffix" value=".jsp"/>
    </bean>
 
<!--    bean注册controller跳转-->
    <bean id="/hello" class="controller.hello"/>
</beans>

3.controller层编写

package controller;
 
 
import org.springframework.web.servlet.mvc.Controller;
import org.springframework.web.servlet.ModelAndView;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
 
//一个继承的controller
//不使用注解
public class hello implements Controller {
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
        //ModelAndView 模型和视图
        ModelAndView mv = new ModelAndView();
        //封装对象，放在ModelAndView中。Model
        mv.addObject("msg","HelloSpringMVC!");
        //封装要跳转的视图，放在ModelAndView中
        mv.setViewName("hello"); //: /WEB-INF/jsp/hello.jsp
        return mv;
    }
}

是的你咋看咋不顺眼 改为注解形式：

package controller;
 
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
 
@Controller
@RequestMapping("/gao")
public class hello {
    @RequestMapping("/hello")
    public String hello(Model model) {
        model.addAttribute("msg", "高低远近");
        return "hello";
    }
}

最终体的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: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
       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，让指定包下的注解生效,由IOC容器统一管理 -->
    <context:component-scan base-package="controller"/>
    <!-- 让Spring MVC不处理静态资源 -->
    <mvc:default-servlet-handler />
    <!--
    支持mvc注解驱动
        在spring中一般采用@RequestMapping注解来完成映射关系
        要想使@RequestMapping注解生效
        必须向上下文中注册DefaultAnnotationHandlerMapping
        和一个AnnotationMethodHandlerAdapter实例
        这两个实例分别在类级别和方法级别处理。
        而annotation-driven配置帮助我们自动完成上述两个实例的注入。
     -->
    <mvc:annotation-driven />
 
    <!-- 视图解析器 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"
          id="internalResourceViewResolver">
        <!-- 前缀 -->
        <property name="prefix" value="/WEB-INF/jsp/" />
        <!-- 后缀 -->
        <property name="suffix" value=".jsp" />
    </bean>
 
</beans>

等会总结 这里还有个蛋疼的问题就是关于jdk编译改码的问题还有lib包问题
参考：https://blog.csdn.net/qq_46906413/article/details/131815212

正常web下项目要有lib文件所有资源识别在此：

是的感觉不是框架阶段 还是javaweb阶段 还得手动导包！
然后tomcat启动测试就行

---

那来看下过程：

来看看之前的：那两个省略的：

    <bean class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping"/>
    <bean class="org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter"/>

两个的作用呢：

1. HandlerMapping
   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
2. 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）
   当然还有其他组件 这就是Springmvc的强大之处例如：
   filter过滤器拦截器
   locale resolve国际化
   multipartresolver文件上传
   ......

@Controller 被spring接管 返回值若为string 则进行跳转
@RequestMapping("") 是一个总的

参考：https://blog.csdn.net/weixin_61034310/article/details/135324203

---

ResultFul

package controller;
 
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;
 
@Controller
public class ResultFulController {
    //    @RequestMapping(value = "/haha/{a}/{b}",method = RequestMethod.DELETE)
    //    等同下面
    //    @DeleteMapping("/haha/{a}/{b}")
 
//    @PostMapping(path = "/haha/{a}/{b}")
//    @PostMapping(value = "/haha/{a}/{b}")
//传参的方式为get 请求post会报405错误
    @PostMapping("/haha/{a}/{b}")
    //@PathVariable 对应ResultFul传参
    public String hello(@PathVariable int a,@PathVariable int b, Model model){
        int res=a+b;
        model.addAttribute("msg",res);
        return "hello";
    }
    @GetMapping("/hahaha/{a}/{b}")
    public String hello2(@PathVariable int a,@PathVariable int b, Model model){
        int res=a+b;
        model.addAttribute("msg",res);
        return "hello";
    }
}

package controller;
 
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import pojo.User;
 
@Controller
@RequestMapping("/user")
public class Usercontroller {
 
 
    @RequestMapping("/one")
    //传参数必须为 user=
    public String haha(@RequestParam("user") String name, Model model) {
        model.addAttribute("msg", name);
        return "hello";
    }
 
    @RequestMapping("/two")
    //传参数必须对应实体类User的字段 name=
    public String haha(User user, Model model) {
        model.addAttribute("msg", user.getName());
        return "hello";
    }
}

---

再来看一个拦截功能 即登录实现

<%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2024/5/21
  Time: 10:24
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
 
<h1>登录页面</h1>
<hr>
 
<body>
<form action="${pageContext.request.contextPath}/user/login">
    用户名：<input type="text" name="username"> <br>
    密码：<input type="password" name="pwd"> <br>
    <input type="submit" value="提交">
</form>
</body>
</html>
 

<%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2024/5/21
  Time: 10:24
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
 
<h1>登录成功页面</h1>
<hr>
 
${user}
<a href="${pageContext.request.contextPath}/user/logout">注销</a>
</body>
</html>
 

<%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2024/5/24
  Time: 15:43
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  <h1>首页</h1>
  <hr>
  <%--登录--%>
  <a href="${pageContext.request.contextPath}/user/jumplogin">登录</a>
  <a href="${pageContext.request.contextPath}/user/jumpSuccess">成功页面</a>
  </body>
</html>
 

package controller;
 
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
 
import javax.servlet.http.HttpSession;
 
@Controller
@RequestMapping("/user")
public class Usercontroller {
 
    //跳转到登陆页面
    @RequestMapping("/jumplogin")
    public String jumpLogin() throws Exception {
        return "login";
    }
 
    //跳转到成功页面
    @RequestMapping("/jumpSuccess")
    public String jumpSuccess() throws Exception {
        return "success";
    }
 
    //登陆提交
    @RequestMapping("/login")
    public String login(HttpSession session, String username, String pwd) throws Exception {
        // 向session记录用户身份信息
        System.out.println("接收前端==="+username);
        session.setAttribute("user", username);
        return "success";
    }
 
    //退出登陆
    @RequestMapping("logout")
    public String logout(HttpSession session) throws Exception {
        // session 过期
        session.invalidate();
        return "login";
    }
}
 

package config;
 
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
 
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
 
public class loginconfig implements HandlerInterceptor {
 
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws ServletException, IOException {
        // 如果是登陆页面则放行
        System.out.println("uri: " + request.getRequestURI());
        if (request.getRequestURI().contains("login")) {
            return true;
        }
 
        HttpSession session = request.getSession();
 
        // 如果用户已登陆也放行
        if(session.getAttribute("user") != null) {
            return true;
        }
 
        // 用户没有登陆跳转到登陆页面
        request.getRequestDispatcher("/WEB-INF/jsp/login.jsp").forward(request, response);
        return false;
    }
 
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
 
    }
 
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
 
    }
}

    <!--关于拦截器的配置-->
    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/**"/>
            <bean id="loginInterceptor" class="config.loginconfig"/>
        </mvc:interceptor>
    </mvc:interceptors>

还有就是文件上传下载 也是死东西可以直接运用：
参考：https://cloud.tencent.com/developer/article/1594124
文章更详细参考：https://pdai.tech/md/spring/spring-x-framework-springmvc.html