SpringMVC 工作原理？

SpimgMVC工作原理

第1步：浏览器发送指定的请求都会交给DispatcherServlet,他会委托其他模块进行真正的业务和数据处理
第2步：DispatcherServlet会查找到HandleMapping,根据浏览器的请求找到对应的Controller，并将请求交给目标Controller
第3步：目标Controller处理完业务后，返回一个ModelAndView给DispatcherServlet
第4步：DispatcherServlet通过ViewResolver视图解析器找到对应的视图对象View
第5步：视图对象View负责渲染，并返回到浏览器

案例分析

下面通过案例图解的方式理解下上面的工作原理

第1步-浏览器请求

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第2、3步-找到对应Controller

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第4、5步-解析视图对象，返回浏览器

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浏览器结果

源码

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类

实体类

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页面

<%@ 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>