Spring MVC

Posted 2021-10-24 zhuqiwei-blog

spring 的 hello world

新建并配置 web.xml，web.xml提供路径与servlet的映射关系

    <servlet>
        <servlet-name>springmvc</servlet-name>
        <servlet-class>
            org.springframework.web.servlet.DispatcherServlet
        </servlet-class>
    </servlet>
    <servlet-mapping>    <!--这里将 / 即任意路径映射到 DispatcherServlet -->
        <servlet-name>springmvc</servlet-name>    <!--这里的name要和上面的springmvc保持一致-->
        <url-pattern>/</url-pattern>    <!-- 这里表示映射的路径，/表示任意路径-->
    </servlet-mapping>

创建springmvc-servlet.xml并配置，这是Spring MVC的 映射配置文件，表示访问路径/index会交给id=indexController的bean处理；id=indexController的bean配置为类：dexController

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
    <bean id="simpleUrlHandlerMapping"
        class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
        <property name="mappings">
            <props>
                <prop key="/index">indexController</prop>
            </props>
        </property>
    </bean>
    <bean id="indexController" class="controller.IndexController"></bean>
</beans>

控制类要实现接口controller，并提供方法handleRequest处理请求

package controller;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller;
 
public class IndexController implements Controller {
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
        ModelAndView mav = new ModelAndView("index.jsp");    //ModelAndView 将视图层和模型层联系在一起，new ModelAndView("index.jsp")表示视图是index.jsp
        mav.addObject("message", "Hello Spring MVC");    //向视图层传递数据，数据的名字是message，内容是 Hello Spring MVC
   　　　return mav; 
    } 
}

准备index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8" isELIgnored="false"%>
 
<h1>${message}</h1>  //这里的message与controller中的message相对应，是变量名

原理图：

跳转

package controller;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;
 
@Controller    //注解，表示该类是一个控制器，这样不用再实现controller接口
public class IndexController {
    @RequestMapping("/index")    //再handleRequest方法前加注解，表示 /index 路径慧映射到该函数上
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
        ModelAndView mav = new ModelAndView("index");
        mav.addObject("message", "Hello Spring MVC");
        return mav;
    }
     
    @RequestMapping("/jump")    //同理将 /jump路径映射到该函数
    public ModelAndView jump() {
        ModelAndView mav = new ModelAndView("redirect:/index");    // redirect:/index 表示服务端跳转，跳转到index
        return mav;
    }    
}

使用session

    @RequestMapping("/check")
    public ModelAndView check(HttpSession session) {
        Integer i = (Integer) session.getAttribute("count");
        if (i == null)
            i = 0;
        i++;
        session.setAttribute("count", i);
        ModelAndView mav = new ModelAndView("check");
        return mav;
    }