【SpringMVC源码】执行源码分析

刺骨的言语ヽ痛彻心扉 2023-02-18 11:55 89阅读 0赞

# 前言 #

Github：[https://github.com/yihonglei/thinking-in-springmvc][https_github.com_yihonglei_thinking-in-springmvc]（文章基于springmvc-xml工程说明）

Spring MVC启动流程：[https://jpeony.blog.csdn.net/article/details/106793070][https_jpeony.blog.csdn.net_article_details_106793070]

# 一 SpringMVC概述 #

Spring MVC封装servlet的MVC Web开发框架，减轻直接操作Servlet的繁琐，提高开发效率。

# 二 Spring MVC执行流程源码 #

## 1、时序图 ##

先上一个简易版本的。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70][]

DispatcherServlet负责请求的转发 ------>  HandlerMapping基于url查找Handler

\------> HandlerAdapter基于Handler查找处理器 ------> 对应url的Handler执行业务

\------> 处理结果交给ViewResolver视图解析器尽心处理 ------> 数据返回给端上进行渲染展示，请求响应完成！

## 2、执行流程详细 ##

web.xml配置如下：

<?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>springMVCDispatcherServlet</servlet-name>
            <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
            
            <init-param>
                <param-name>contextConfigLocation</param-name>
                <param-value>classpath:spring-mvc.xml</param-value>
            </init-param>
            <load-on-startup>1</load-on-startup>
        </servlet>
    
        
        <servlet-mapping>
            <servlet-name>springMVCDispatcherServlet</servlet-name>
            <url-pattern>*.do</url-pattern>
        </servlet-mapping>
    
        <display-name></display-name>
        <welcome-file-list>
            <welcome-file>index.jsp</welcome-file>
        </welcome-file-list>
    </web-app>

spring-mvc.xml配置如下：

<?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:tx="http://www.springframework.org/schema/tx"
           xsi:schemaLocation="
                http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
                http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
                http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">
        
        <bean id="urlMapping"
              class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
            <property name="mappings">
                <props>
                    <prop key="helloWorld.do">helloWorldController</prop>
                </props>
            </property>
        </bean>
    
        
        <bean id="viewResolver"
              class="org.springframework.web.servlet.view.InternalResourceViewResolver">
            <property name="viewClass">
                <value>org.springframework.web.servlet.view.InternalResourceView</value>
            </property>
        </bean>
    
        
        <bean id="helloWorldController"
              class="com.jpeony.springmvc.controller.HelloWorldController">
            <property name="helloWorld">
                <value>HelloWorld</value>
            </property>
            <property name="viewPage">
                <value>/WEB-INF/jsp/index.jsp</value>
            </property>
        </bean>
    </beans>

上面通过简易时序图了解了大概流程，下面详细搞下请求从哪个代码进来的，在哪个代码处理，从哪个代码出去的。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 1][]

假设用Tomcat容器，SpringMVC包装Servlet，应用靠web容器Tomcat启动。

应用请求过来先到Tomcat，Tomcat 默认使用NIO模型，请求最后访问到Servlet的service()方法。

Spring MVC请求故事从Servlet的service()方法开始。

先看下DispatcherServlet的结构关系图。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 2][]

每一次的请求，根据Servlet标准，都会访问Servlet的service()方法，根据Servlet继承实现关系，SpringMVC的FrameworkServlet

重写了service()方法。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 3][]

调用父类HttpServlet的service()方法。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 4][]

假设使用的是Post请求，doPost()在FrameworkServlet中实现。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 5][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 6][]

调用FrameworkServlet\#doService()方法，DispatcherServlet重写doService()。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 7][]

请求具体处理在DispatcherServlet\#doDispatch()方法中，代码有点长，分开截图。

获取执行责任链。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 8][]

获取执行适配器SimpleControllerHandlerAdapter，通过handle()调用实际处理器。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 9][]

继续往下走。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 10][]

这里调用我们自己的Controller的handleRequest()方法。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 11][]

久违已久的Controller，终于进来了。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 12][] 在doDispatch()的下面部分代码，对返回结果进行处理，对ModelAndView进行处理。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 13][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 14][]

render对结果进行处理，解析视图名称，以及将结果塞在response返回。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 15][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 16][]

终于，进到了spring-mvc.xml里面配置的InternalResourceViewResolver视图解析器中。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lobF9qeHk_size_16_color_FFFFFF_t_70 17][]

返回视图地址、内容、然后端上解析、展现。

[https_github.com_yihonglei_thinking-in-springmvc]: https://github.com/yihonglei/thinking-in-springmvc
[https_jpeony.blog.csdn.net_article_details_106793070]: https://jpeony.blog.csdn.net/article/details/106793070
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