springMVC框架原理解析

整体工作原理

XML方式

spring-mvc:XXVERsion.jar里的spring.handlers文件里标明解析方式

http\://www.springframework.org/schema/mvc=org.springframework.web.servlet.config.MvcNamespaceHandler

欢迎大家来到IT世界,在知识的湖畔探索吧!

使用RequestMappingHandlerMapping来对mvc的注解进行扫描

欢迎大家来到IT世界,在知识的湖畔探索吧!public class MvcNamespaceHandler extends NamespaceHandlerSupport {
 @Override
 public void init() {
 //这里注册使用RequestMappingHandlerMapping来进行MVC的处理
 registerBeanDefinitionParser("annotation-driven", new AnnotationDrivenBeanDefinitionParser());
 registerBeanDefinitionParser("default-servlet-handler", new DefaultServletHandlerBeanDefinitionParser());
 registerBeanDefinitionParser("interceptors", new InterceptorsBeanDefinitionParser());
 registerBeanDefinitionParser("resources", new ResourcesBeanDefinitionParser());
 registerBeanDefinitionParser("view-controller", new ViewControllerBeanDefinitionParser());
 registerBeanDefinitionParser("redirect-view-controller", new ViewControllerBeanDefinitionParser());
 registerBeanDefinitionParser("status-controller", new ViewControllerBeanDefinitionParser());
 registerBeanDefinitionParser("view-resolvers", new ViewResolversBeanDefinitionParser());
 registerBeanDefinitionParser("tiles-configurer", new TilesConfigurerBeanDefinitionParser());
 registerBeanDefinitionParser("freemarker-configurer", new FreeMarkerConfigurerBeanDefinitionParser());
 registerBeanDefinitionParser("velocity-configurer", new VelocityConfigurerBeanDefinitionParser());
 registerBeanDefinitionParser("groovy-configurer", new GroovyMarkupConfigurerBeanDefinitionParser());
 registerBeanDefinitionParser("script-template-configurer", new ScriptTemplateConfigurerBeanDefinitionParser());
 registerBeanDefinitionParser("cors", new CorsBeanDefinitionParser());
 }
}

注解

注解形式的SpringMvc使用@EnableWebMvc

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(DelegatingWebMvcConfiguration.class)
public @interface EnableWebMvc {
}

DelegatingWebMvcConfiguration是一个Configuration形式的配置，里面以@Bean的方式注册了RequestMappingHandlerMapping

看下源码：

WebMvcConfigurationSupport是DelegatingWebMvcConfiguration的父类

欢迎大家来到IT世界,在知识的湖畔探索吧!public class WebMvcConfigurationSupport implements ApplicationContextAware, ServletContextAware {
 //向容器注入RequestMappingHandlerMapping
 @Bean
 public RequestMappingHandlerMapping requestMappingHandlerMapping() {
 RequestMappingHandlerMapping mapping = createRequestMappingHandlerMapping();
 mapping.setOrder(0);
 mapping.setInterceptors(getInterceptors());
 mapping.setContentNegotiationManager(mvcContentNegotiationManager());
 mapping.setCorsConfigurations(getCorsConfigurations());
 PathMatchConfigurer configurer = getPathMatchConfigurer();
 if (configurer.isUseSuffixPatternMatch() != null) {
 mapping.setUseSuffixPatternMatch(configurer.isUseSuffixPatternMatch());
 }
 if (configurer.isUseRegisteredSuffixPatternMatch() != null) {
 mapping.setUseRegisteredSuffixPatternMatch(configurer.isUseRegisteredSuffixPatternMatch());
 }
 if (configurer.isUseTrailingSlashMatch() != null) {
 mapping.setUseTrailingSlashMatch(configurer.isUseTrailingSlashMatch());
 }
 UrlPathHelper pathHelper = configurer.getUrlPathHelper();
 if (pathHelper != null) {
 mapping.setUrlPathHelper(pathHelper);
 }
 PathMatcher pathMatcher = configurer.getPathMatcher();
 if (pathMatcher != null) {
 mapping.setPathMatcher(pathMatcher);
 }
 return mapping;
 }
}

DispatcherServlet处理请求

public class DispatcherServlet extends FrameworkServlet {
 /** List of HandlerMappings used by this servlet */
 private List<HandlerMapping> handlerMappings;
 /** List of HandlerAdapters used by this servlet */
 private List<HandlerAdapter> handlerAdapters;
 protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
 //获取RequestMappingHandlerMapping，然后再获取HandlerExecutionChain
 HandlerExecutionChain mappedHandler = getHandler(processedRequest);
 //获取RequestMappingHandlerAdapter，真正处理请求的逻辑执行者
 HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
 //执行
 mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
 applyDefaultViewName(processedRequest, mv);
 mappedHandler.applyPostHandle(processedRequest, response, mv);
 }
 }
}

下面再来看几个重要的类

HandlerMapping

AnnotationDrivenBeanDefinitionParser解析xml注解会向BeanFactory里注册内置的HandlerMapping

• SimpleUrlHandlerMapping
• RequestMappingHandlerMapping
• BeanNameUrlHandlerMapping
• WebMvcConfigurationSupport.EmptyHandlerMapping

public BeanDefinition parse(Element element, ParserContext parserContext) {
//...省略其他代码
//注册最终要的RequestMappingHandlerMapping到容器中
parserContext.registerComponent(new BeanComponentDefinition(handlerMappingDef, HANDLER_MAPPING_BEAN_NAME));
 parserContext.registerComponent(new BeanComponentDefinition(handlerAdapterDef, HANDLER_ADAPTER_BEAN_NAME));
//注册默认的HandlerMapping
MvcNamespaceUtils.registerDefaultComponents(parserContext, source);
}
}

• 其中最终要的就是RequestMappingHandlerMapping了。

RequestMappingHandlerMapping

RequestMappingHandlerMapping是用来处理SpringMVC注解（@Controller、@RequestMapping）的核心类

RequestMappingHandlerMapping会扫描所有@Controller和@RequestMapping，将处理请求的方法封装为HandlerMethod，存储在MappingRegistry里。

而MappingRegistry则是维护了一个url和对应处理方法的Map，Map> nameLookup

具体的逻辑可查看 RequestMappingHandlerMapping父类AbstractHandlerMethodMapping的afterPropertiesSet方法，这里会做前面的初始化工作

HandlerExecutionChain

HandlerExecutionChain的结构

• handler:HandlerMethod
• bean 实际的controller
• method url请求对应的method
• parameters 方法对应的参数
• interceptors：HandlerInterceptor[]