springboot情操陶冶-web配置(二)
2019-08-14

承接前文springboot情操陶冶-web配置(一),本文将在前文的基础上分析下mvc的相关应用

MVC简单例子

直接编写一个Controller层的代码,返回格式为json

package com.example.demo.web.controller;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;import org.springframework.web.bind.annotation.ResponseBody;import java.util.HashMap;import java.util.Map;/** * @author nanco * ------------- * ------------- * @create 2018/9/4 **/@Controller@RequestMapping("/boot")@ResponseBodypublic class DemoController { @RequestMapping(value = "/hello", method = RequestMethod.GET) public Map<String, String> helloWorld() { Map<String, String> result = new HashMap<>(); result.put("springboot", "hello world"); return result; }}

运行之后,客户端工具HTTP访问链接http://127.0.0.1:9001/demoWeb/boot/hello便可得到以下的简单结果

{"springboot":"hello world"}

源码剖析

我们都知道springmvc最核心的组件便是DispatcherServlet,其本质是个Servlet组件,也包含了处理前端请求的逻辑,具体的可参照SpringMVC源码情操陶冶-DispatcherServlet。本文则讲解Springboot创建DispatcherServlet以及MVC配置的过程

DispatcherServletAutoConfiguration

首先需要配置DispatcherServlet组件,分为几个步骤来看


No.1 脑头注解了解下

@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)@Configuration@ConditionalOnWebApplication(type = Type.SERVLET)@ConditionalOnClass(DispatcherServlet.class)@AutoConfigureAfter(ServletWebServerFactoryAutoConfiguration.class)@EnableConfigurationProperties(ServerProperties.class)public class DispatcherServletAutoConfiguration {}

由以上的注解可得知,其需要在ServletWebServerFactoryAutoConfiguration类注入至bean工厂后方可继续,这就和前文关联起来了。


No.2 DispatcherServletConfiguration内部类

@Configuration @Conditional(DefaultDispatcherServletCondition.class) @ConditionalOnClass(ServletRegistration.class) @EnableConfigurationProperties(WebMvcProperties.class) protected static class DispatcherServletConfiguration { // 引入了spring.mvc为开头的配置 private final WebMvcProperties webMvcProperties; private final ServerProperties serverProperties; public DispatcherServletConfiguration(WebMvcProperties webMvcProperties, ServerProperties serverProperties) { this.webMvcProperties = webMvcProperties; this.serverProperties = serverProperties; } // 直接创建DispatcherServlet并注入至bean工厂 @Bean(name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME) public DispatcherServlet dispatcherServlet() { DispatcherServlet dispatcherServlet = new DispatcherServlet(); // 对应spring.mvc.dispatch-options-request dispatcherServlet.setDispatchOptionsRequest( this.webMvcProperties.isDispatchOptionsRequest()); // 对应spring.mvc.dispatch-trace-request dispatcherServlet.setDispatchTraceRequest( this.webMvcProperties.isDispatchTraceRequest()); // 对应spring.mvc.throw-exception-if-no-handler-found dispatcherServlet.setThrowExceptionIfNoHandlerFound( this.webMvcProperties.isThrowExceptionIfNoHandlerFound()); return dispatcherServlet; } // 创建名为multipartResolver的用于文件请求 @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; } // 获取server.servlet.path表明DispatcherServlet的拦截路径 @Bean public DispatcherServletPathProvider mainDispatcherServletPathProvider() { return () -> DispatcherServletConfiguration.this.serverProperties.getServlet() .getPath(); } }

很简单,就是创建了DispatcherServlet,那么如何被注入至tomcat的servlet集合中呢


No.3 DispatcherServletRegistrationConfiguration内部类

@Configuration @Conditional(DispatcherServletRegistrationCondition.class) @ConditionalOnClass(ServletRegistration.class) @EnableConfigurationProperties(WebMvcProperties.class) @Import(DispatcherServletConfiguration.class) protected static class DispatcherServletRegistrationConfiguration { private final ServerProperties serverProperties; private final WebMvcProperties webMvcProperties; private final MultipartConfigElement multipartConfig; public DispatcherServletRegistrationConfiguration( ServerProperties serverProperties, WebMvcProperties webMvcProperties, ObjectProvider<MultipartConfigElement> multipartConfigProvider) { this.serverProperties = serverProperties; this.webMvcProperties = webMvcProperties; this.multipartConfig = multipartConfigProvider.getIfAvailable(); } // 对DispatcherServlet注入至tomcat等容器中 @Bean(name = DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME) @ConditionalOnBean(value = DispatcherServlet.class, name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME) public ServletRegistrationBean<DispatcherServlet> dispatcherServletRegistration( DispatcherServlet dispatcherServlet) { // 同server.servlet.path,默认为/ ServletRegistrationBean<DispatcherServlet> registration = new ServletRegistrationBean<>( dispatcherServlet, this.serverProperties.getServlet().getServletMapping()); registration.setName(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME); // 读取spring.mvc.servlet.load-on-startup,默认为-1 registration.setLoadOnStartup( this.webMvcProperties.getServlet().getLoadOnStartup()); if (this.multipartConfig != null) { registration.setMultipartConfig(this.multipartConfig); } return registration; } }

由上述代码得知,将servlet注入至tomcat容器是通过ServletContextInitializer接口的实现类ServletRegistrationBean来实现的,具体的本文不展开,不过如果用户想把Servlet或者Filter注入至tomcat,则常用此Bean来操作即可

WebMvcAutoConfiguration

DispatcherServlet组件创建并注入至web容器后,接下来便是对mvc的相关配置,笔者也按几个步骤来分析


No.1 脑壳注解看一下

@Configuration@ConditionalOnWebApplication(type = Type.SERVLET)@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class, ValidationAutoConfiguration.class })public class WebMvcAutoConfiguration {}

此配置也是根据上文中的DispatcherServletAutoConfiguration注入至bean工厂后再生效。


No.2 Filter集合

1.HiddenHttpMethodFilter-隐性传播PUT/DELETE/PATCH请求

@Bean @ConditionalOnMissingBean(HiddenHttpMethodFilter.class) public OrderedHiddenHttpMethodFilter hiddenHttpMethodFilter() { // 默认对post请求的包读取_method参数指定的方法,然后再作转换 return new OrderedHiddenHttpMethodFilter(); }

隐性的通过methodParam参数来传播PUT/DELETE/PATCH请求,默认参数名为_method,也可用户自行配置

2.HttpPutFormContentFilter-显性响应PUT/DELETE/PATCH请求

// spring.mvc.formcontent.putfilter.enabled不指定或者值不为false则生效 @Bean @ConditionalOnMissingBean(HttpPutFormContentFilter.class) @ConditionalOnProperty(prefix = "spring.mvc.formcontent.putfilter", name = "enabled", matchIfMissing = true) public OrderedHttpPutFormContentFilter httpPutFormContentFilter() { // 直接对PUT/DELETE/PATCH请求进行响应,其order值大于OrderedHiddenHttpMethodFilter return new OrderedHttpPutFormContentFilter(); }

其一般与上述的OrderedHiddenHttpMethodFilter搭配使用,其order值大于前者所以排在后面响应PUT等请求。温馨提示:此处只是注册了filter到bean工厂,并没有被注入至tomcat等web容器中,用户如果想支持上述的请求方法,可以考虑通过ServletRegistrationBean/FilterRegistrationBean来进行注入


No.3 EnableWebMvcConfiguration内部类,其类同@EnableWebMvc注解,类同我们常用spring配置的mvc:annotation-driven。由于代码过多,就挑选几个来看

@Configuration public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration { // 注册RequestMappingHandlerAdapter组件 @Bean @Override public RequestMappingHandlerAdapter requestMappingHandlerAdapter() { RequestMappingHandlerAdapter adapter = super.requestMappingHandlerAdapter(); adapter.setIgnoreDefaultModelOnRedirect(this.mvcProperties == null || this.mvcProperties.isIgnoreDefaultModelOnRedirect()); return adapter; } // 注册RequestMappingHanlderMapping组件 @Bean @Primary @Override public RequestMappingHandlerMapping requestMappingHandlerMapping() { // Must be @Primary for MvcUriComponentsBuilder to work return super.requestMappingHandlerMapping(); } // 校验器组件 @Bean @Override public Validator mvcValidator() { if (!ClassUtils.isPresent("javax.validation.Validator", getClass().getClassLoader())) { return super.mvcValidator(); } return ValidatorAdapter.get(getApplicationContext(), getValidator()); } // 异常处理组件 @Override protected ExceptionHandlerExceptionResolver createExceptionHandlerExceptionResolver() { if (this.mvcRegistrations != null && this.mvcRegistrations .getExceptionHandlerExceptionResolver() != null) { return this.mvcRegistrations.getExceptionHandlerExceptionResolver(); } return super.createExceptionHandlerExceptionResolver(); } }

主要是用来注册响应前端请求的插件集合,具体的怎么整合可见笔者置顶的spring文章,里面有提,就不在此处展开了温馨提示:笔者此处提醒下此类是DelegatingWebMvcConfiguration的实现类,其本身也被注解@Configuration修饰,其内部的setConfigurers()方法有助于集结所有实现了WebMvcConfigurer接口的集合,所以用户可通过实现此接口来扩展mvc的相关配置

private final WebMvcConfigurerComposite configurers = new WebMvcConfigurerComposite(); @Autowired(required = false) public void setConfigurers(List<WebMvcConfigurer> configurers) { if (!CollectionUtils.isEmpty(configurers)) { this.configurers.addWebMvcConfigurers(configurers); } }


No.4 WebMvcAutoConfigurationAdapter内部类(WebMvcConfigurer接口实现类)-在上述的MVC组件的基础上新增其他的组件,包含视图组件、消息处理器组件等。限于代码过长,笔者此处也挑选几个来看

// 消息处理器集合配置 @Override public void configureMessageConverters(List<HttpMessageConverter<?>> converters) { converters.addAll(this.messageConverters.getConverters()); } // 对路径请求的配置 @Override public void configurePathMatch(PathMatchConfigurer configurer) { // 对应spring.mvc.pathmatch.use-suffix-pattern,默认为false configurer.setUseSuffixPatternMatch( this.mvcProperties.getPathmatch().isUseSuffixPattern()); // 对应spring.mvc.patchmatch.use-registered-suffix-pattern,默认为false configurer.setUseRegisteredSuffixPatternMatch( this.mvcProperties.getPathmatch().isUseRegisteredSuffixPattern()); } // 创建jsp视图解析器 @Bean @ConditionalOnMissingBean public InternalResourceViewResolver defaultViewResolver() { InternalResourceViewResolver resolver = new InternalResourceViewResolver(); // 对应spring.mvc.view.prefix,默认为空 resolver.setPrefix(this.mvcProperties.getView().getPrefix()); // 对应spring.mvc.view.suffix,默认为空 resolver.setSuffix(this.mvcProperties.getView().getSuffix()); return resolver; } // 静态文件访问配置 @Override public void addResourceHandlers(ResourceHandlerRegistry registry) { // 对应spring.resource.add-mappings,默认为true if (!this.resourceProperties.isAddMappings()) { logger.debug("Default resource handling disabled"); return; } Duration cachePeriod = this.resourceProperties.getCache().getPeriod(); CacheControl cacheControl = this.resourceProperties.getCache() .getCachecontrol().toHttpCacheControl(); if (!registry.hasMappingForPattern("/webjars/**")) { customizeResourceHandlerRegistration(registry .addResourceHandler("/webjars/**") .addResourceLocations("classpath:/META-INF/resources/webjars/") .setCachePeriod(getSeconds(cachePeriod)) .setCacheControl(cacheControl)); } // 对应spring.mvc.static-path-pattern,默认为/** String staticPathPattern = this.mvcProperties.getStaticPathPattern(); if (!registry.hasMappingForPattern(staticPathPattern)) { customizeResourceHandlerRegistration( registry.addResourceHandler(staticPathPattern) // 对应spring.resources.static-locations .addResourceLocations(getResourceLocations( this.resourceProperties.getStaticLocations())) .setCachePeriod(getSeconds(cachePeriod)) .setCacheControl(cacheControl)); } } // 欢迎界面配置,一般可在static或者项目根目录下配置index.html界面即可 @Bean public WelcomePageHandlerMapping welcomePageHandlerMapping( ApplicationContext applicationContext) { return new WelcomePageHandlerMapping( new TemplateAvailabilityProviders(applicationContext), applicationContext, getWelcomePage(), this.mvcProperties.getStaticPathPattern()); }

小结

本文主要讲解了mvc的springboot自动配置过程,读者主要关注DispatcherServlet组件和消息处理等组件的bean工厂配置即可。如果用户也想自定义去扩展mvc的相关配置,可自行去实现WebMvcConfigurer接口即可,样例如下

package com.example.demo.web.config;import org.springframework.http.converter.HttpMessageConverter;import org.springframework.web.servlet.HandlerExceptionResolver;import org.springframework.web.servlet.config.annotation.InterceptorRegistry;import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;import java.util.List;/** * @author nanco * ------------- * ------------- * @create 2018/9/5 **/public class BootWebMvcConfigurer implements WebMvcConfigurer { @Override public void addInterceptors(InterceptorRegistry registry) { } @Override public void configureMessageConverters(List<HttpMessageConverter<?>> converters) { } @Override public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) { }}

本文也讲述了如果用户想扩展相应的Filter或者Servlet,可使用FilterRegistrationBean/ServletRegistrationBean,样例如下

package com.example.demo.web.config;import org.springframework.boot.web.servlet.FilterRegistrationBean;import org.springframework.boot.web.servlet.ServletRegistrationBean;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.web.filter.OncePerRequestFilter;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.Servlet;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.IOException;/** * @author nanco * ------------- * ------------- * @create 2018/9/5 **/@Configurationpublic class ServletFilterBeans { // only intercept /simple/ @Bean("simpleServlet") public ServletRegistrationBean<Servlet> simpleServlet() { return new ServletRegistrationBean<>(new SimpleServlet(), "/simple/"); } // intercept /simple、/simple/、/simple/ha etc. @Bean("simpleFilter") public FilterRegistrationBean<Filter> simpleFilter() { FilterRegistrationBean bean = new FilterRegistrationBean<>(); bean.setFilter(new SimpleFilter()); bean.addUrlPatterns("/simple/*"); return bean; } private static class SimpleServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { System.out.println("doService path: " + req.getRequestURI()); super.doGet(req, resp); } } private static class SimpleFilter extends OncePerRequestFilter { @Override protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException { System.out.println("filter path: " + request.getRequestURI()); filterChain.doFilter(request, response); } }}