原理概述
Springboot向外界提供web服務，底層依賴了springframework中的web模塊（包含但不限于spring mvc核心類DispatcherServlet）來實現
那么springboot在什么時機向容器注入DispatcherServlet這個核心類的呢
注入的流程還是遵循了自動裝配流程，在springboot框架里默認提供了該自動裝配的支持
在jar包里的spring.factories文件里有個 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";
// ... 省略代碼
}在DispatcherServletAutoConfiguration中有兩個內部類（配置類） DispatcherServletConfiguration、DispatcherServletRegistrationConfiguration和兩個對應的Condition類DefaultDispatcherServletCondition、DispatcherServletRegistrationCondition
DispatcherServletConfiguration
DispatcherServletConfiguration是DispatcherServletAutoConfiguration 的一個內部類，并被 @Configuration標注，會被容器自動掃描到；其有兩個方法： 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)：配置類采用Lite模式
- @Conditional(DefaultDispatcherServletCondition.class)：根據DefaultDispatcherServletCondition類返回值計算是否要注入，主要邏輯是檢驗Spring容器中是否已經存在一個名字為"dispatcherServlet"的DispatcherServlet
- @ConditionalOnClass(ServletRegistration.class)：容器中必須要有ServletRegistration類
- @EnableConfigurationProperties({ HttpProperties.class, WebMvcProperties.class })：加載HttpProperties和WebMvcProperties
@B：注入 MultipartResolver 解析類
DispatcherServletRegistrationConfiguration
該類注入的邏輯與DispatcherServletConfiguration 相同，只不過在類上注解了 @Import(DispatcherServletConfiguration.class)那么這兩個類定義就有了先后順序
@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<MultipartConfigElement> multipartConfig) {
DispatcherServletRegistrationBean registration = new DispatcherServletRegistrationBean(dispatcherServlet,
webMvcProperties.getServlet().getPath());
// 設置名稱
registration.setName(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME);
registration.setLoadOnStartup(webMvcProperties.getServlet().getLoadOnStartup());
multipartConfig.ifAvailable(registration::setMultipartConfig);
return registration;
}
}其中，DispatcherServletRegistrationBean繼承自ServletRegistrationBean，主要為DispatcherServlet提供服務。DispatcherServletRegistrationBean和DispatcherServlet都提供了注冊Servlet并公開DispatcherServletPath信息的功能
面試點
spring mvc和spring boot的關系，相信讀了上面的文章會說出一兩點；
到此這篇關于Springboot自動裝配之注入DispatcherServlet的文章就介紹到這了,更多相關Springboot注入DispatcherServlet內容請搜索html5模板網以前的文章希望大家以后多多支持html5模板網！