How does springmvc work?

The working principle of springmvc is: 1. The browser sends a request to DispatcherServlet; 2. Find the corresponding Controller according to the request; 3. Return to ModelAndView; 4. Find the corresponding view object View and render it; 5. Return to browser.

SpringMVC working principle:

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1. The specified request sent by the browser will be handed over to DispatcherServlet, which will entrust other modules to perform real business and data processing;

2. DispatcherServlet will find HandleMapping, find the corresponding Controller according to the browser's request, and The request is handed over to the target Controller;

3. After the target Controller completes the business, it returns a ModelAndView to the DispatcherServlet;

4. The DispatcherServlet finds the corresponding view object View through the ViewResolver view parser;

4. The view object View is responsible for rendering and returning to the browser.

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Let’s take a look at the code example:

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_2_5.xsd"
    version="2.5">
    <display-name>springmvc</display-name>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
    </welcome-file-list>
    <!-- spring入口 -->
    <servlet>
        <servlet-name>springmvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <!-- 项目启动时，就加载并实例化 -->
        <load-on-startup>1</load-on-startup>
    </servlet>

    <!-- 拦截所有不包括jsp的请求 -->
    <servlet-mapping>
        <servlet-name>springmvc</servlet-name>
        <url-pattern>*.do</url-pattern>
    </servlet-mapping>

</web-app>

springmvc-servlet.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:aop="http://www.springframework.org/schema/aop"
    xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"
    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/aop
        http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/tx
        http://www.springframework.org/schema/tx/spring-tx.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd">

        <!-- springmvc注解驱动 -->
        <mvc:annotation-driven></mvc:annotation-driven>

        <!-- 开启注解扫描 -->
        <context:component-scan base-package="cn.itcast.controller"></context:component-scan>

        <!-- 配置试图解析器
            prefix:指定试图所在目录
            suffix:指定视图的后缀名
            例如：prifex="/WEB-INF/jsp/",suffix=".jsp",当viewname="test"时，跳转到/WEB-INF/jsp/test.jsp页面
         -->
        <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
            <property name="prefix" value="/WEB-INF/jsp/"></property>
            <property name="suffix" value=".jsp"></property>
        </bean>
</beans>

UserControll class

@Controller
@RequestMapping("user")
public class UserController {
    @RequestMapping("findAllUsers")
    public ModelAndView findAllUsers() {
        ModelAndView mv = new ModelAndView();
        ArrayList<User> users = new ArrayList<User>();
        for (int i = 0; i < 5; i++) {
            User user = new User();
            user.setUsername("zs" + i);
            user.setAge(20 + i);
            user.setIncome(16000.0+i*100);
            user.setIsMarry(false);
            user.setHobby(new String[] { "篮球"+i, "足球"+i });
            users.add(user);
        }
        mv.addObject("users", users);
        mv.setViewName("users");
        return mv;
    }
}

Entity class

public class User implements Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    private String username;
    private Integer age;
    private Boolean isMarry;
    private Double income;
    private String[] hobby;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Boolean getIsMarry() {
        return isMarry;
    }

    public void setIsMarry(Boolean isMarry) {
        this.isMarry = isMarry;
    }

    public Double getIncome() {
        return income;
    }

    public void setIncome(Double income) {
        this.income = income;
    }

    public String[] getHobby() {
        return hobby;
    }

    public void setHobby(String[] hobby) {
        this.hobby = hobby;
    }

    @Override
    public String toString() {
        return "User [username=" + username + ", age=" + age + ", isMarry=" + isMarry + ", income=" + income
                + ", hobby=" + Arrays.toString(hobby) + "]";
    }

}

jsp page

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<link rel="stylesheet" type="text/css" href="/css/user.css" />
</head>
<body>
    <table id="customers">
        <tr>
            <th>用户名</th>
            <th>年龄</th>
            <th>收入</th>
            <th>婚姻状态</th>
            <th>兴趣爱好</th>
        </tr>
        <!-- 遍历后台传递的集合数据 -->
        <c:forEach items="${users}" var="user">
            <tr>
                <td>${user.username}</td>
                <td>${user.age}</td>
                <td>${user.income}</td>
                <!-- 判婚姻状态 -->
                <td><c:choose>
                        <c:when test="${user.isMarry}">已婚</c:when>
                        <c:otherwise>未婚</c:otherwise>
                    </c:choose>
                </td>

                <td>
                <!-- 再次遍历用户爱好 -->
                <c:forEach items="${user.hobby}" var="hobby" varStatus="status">
                    ${hobby} 
                    <!-- 如果不是最后一个爱好，则加上逗号，否则就不加 -->
                    <c:if test="${!status.last}">,</c:if>
                </c:forEach>
                </td>
            </tr>
        </c:forEach>
    </table>
</body>
</html>

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