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Springboot自动装配之注入DispatcherServlet怎么实现

发表于:2025-01-16 作者:千家信息网编辑
千家信息网最后更新 2025年01月16日,这篇文章主要介绍"Springboot自动装配之注入DispatcherServlet怎么实现",在日常操作中,相信很多人在Springboot自动装配之注入DispatcherServlet怎么实现
千家信息网最后更新 2025年01月16日Springboot自动装配之注入DispatcherServlet怎么实现

这篇文章主要介绍"Springboot自动装配之注入DispatcherServlet怎么实现",在日常操作中,相信很多人在Springboot自动装配之注入DispatcherServlet怎么实现问题上存在疑惑,小编查阅了各式资料,整理出简单好用的操作方法,希望对大家解答"Springboot自动装配之注入DispatcherServlet怎么实现"的疑惑有所帮助!接下来,请跟着小编一起来学习吧!

原理概述

Springboot向外界提供web服务,底层依赖了springframework中的web模块(包含但不限于spring mvc核心类DispatcherServlet)来实现

那么springboot在什么时机向容器注入DispatcherServlet这个核心类的呢
注入的流程还是遵循了自动装配流程,在springboot框架里默认提供了该自动装配的支持

在jar包里的spring.factories文件里有个 org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration配置

@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)@Configuration(proxyBeanMethods = false)@ConditionalOnWebApplication(type = Type.SERVLET)@ConditionalOnClass(DispatcherServlet.class)@AutoConfigureAfter(ServletWebServerFactoryAutoConfiguration.class)public class DispatcherServletAutoConfiguration {        /*         * The bean name for a DispatcherServlet that will be mapped to the root URL "/"         */        public static final String DEFAULT_DISPATCHER_SERVLET_BEAN_NAME = "dispatcherServlet";        /*         * The bean name for a ServletRegistrationBean for the DispatcherServlet "/"         *        public static final String DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME = "dispatcherServletRegistration";        // ... 省略代码        }

在DispatcherServletAutoConfiguration中有两个内部类(配置类) DispatcherServletConfiguration、DispatcherServletRegistrationConfiguration和两个对应的Condition类DefaultDispatcherServletCondition、DispatcherServletRegistrationCondition

DispatcherServletConfiguration

DispatcherServletConfiguration是DispatcherServletAutoConfiguration 的一个内部类,并被 @Configuration标注,会被容器自动扫描到;其有两个方法: 1、dispatcherServlet;2、multipartResolver

    @Configuration(proxyBeanMethods = false)        @Conditional(DefaultDispatcherServletCondition.class)        @ConditionalOnClass(ServletRegistration.class)        @EnableConfigurationProperties({ HttpProperties.class, WebMvcProperties.class })        protected static class DispatcherServletConfiguration {// @A                @Bean(name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)                public DispatcherServlet dispatcherServlet(HttpProperties httpProperties, WebMvcProperties webMvcProperties) {                        DispatcherServlet dispatcherServlet = new DispatcherServlet();                        dispatcherServlet.setDispatchOptionsRequest(webMvcProperties.isDispatchOptionsRequest());                        dispatcherServlet.setDispatchTraceRequest(webMvcProperties.isDispatchTraceRequest());                        dispatcherServlet.setThrowExceptionIfNoHandlerFound(webMvcProperties.isThrowExceptionIfNoHandlerFound());                        dispatcherServlet.setPublishEvents(webMvcProperties.isPublishRequestHandledEvents());                        dispatcherServlet.setEnableLoggingRequestDetails(httpProperties.isLogRequestDetails());                        return dispatcherServlet;                }// @B                @Bean                @ConditionalOnBean(MultipartResolver.class)                @ConditionalOnMissingBean(name = DispatcherServlet.MULTIPART_RESOLVER_BEAN_NAME)                public MultipartResolver multipartResolver(MultipartResolver resolver) {                        // Detect if the user has created a MultipartResolver but named it incorrectly                        return resolver;                }        }

@A:

  • @Configuration(proxyBeanMethods = false):配置类采用Lite模式

  • @Conditional(DefaultDispatcherServletCondition.class):根据DefaultDispatcherServletCondition类返回值计算是否要注入,主要逻辑是检验Spring容器中是否已经存在一个名字为"dispatcherServlet"的DispatcherServlet

  • @ConditionalOnClass(ServletRegistration.class):容器中必须要有ServletRegistration类

  • @EnableConfigurationProperties({ HttpProperties.class, WebMvcProperties.class }):加载HttpProperties和WebMvcProperties

@B:注入 MultipartResolver 解析类

DispatcherServletRegistrationConfiguration

该类注入的逻辑与DispatcherServletConfiguration 相同,只不过在类上注解了 @Import(DispatcherServletConfiguration.class)那么这两个类定义就有了先后顺序

@Configuration(proxyBeanMethods = false)        @Conditional(DispatcherServletRegistrationCondition.class)        @ConditionalOnClass(ServletRegistration.class)        @EnableConfigurationProperties(WebMvcProperties.class)        @Import(DispatcherServletConfiguration.class) //@A        protected static class DispatcherServletRegistrationConfiguration {                @Bean(name = DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME)                @ConditionalOnBean(value = DispatcherServlet.class, name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)                public DispatcherServletRegistrationBean dispatcherServletRegistration(DispatcherServlet dispatcherServlet,                                WebMvcProperties webMvcProperties, ObjectProvider multipartConfig) {                        DispatcherServletRegistrationBean registration = new DispatcherServletRegistrationBean(dispatcherServlet,                                        webMvcProperties.getServlet().getPath());                        // 设置名称                                    registration.setName(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME);                        registration.setLoadOnStartup(webMvcProperties.getServlet().getLoadOnStartup());                        multipartConfig.ifAvailable(registration::setMultipartConfig);                        return registration;                }        }

其中,DispatcherServletRegistrationBean继承自ServletRegistrationBean,主要为DispatcherServlet提供服务。DispatcherServletRegistrationBean和DispatcherServlet都提供了注册Servlet并公开DispatcherServletPath信息的功能

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