SpringMVC源码解析（一）

亦凉 2024-04-18 20:39 76阅读 0赞

> 注意，读完本篇文章需要很长很长时间

#### 源码阅读环境搭建 ####

为了简单起见，再一个就是现在这个年代也没有啥项目使用JSP了。所以本次分析使用SpringBoot结合thymeleaf来搞

首先pom文件依赖

application.properties

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 <td><pre>1 2 3 4 5 6 </pre></td> 
 <td><pre>spring.thymeleaf.prefix=classpath:/templates/ spring.thymeleaf.suffix=.html spring.thymeleaf.mode=LEGACYHTML5 spring.thymeleaf.encoding=UTF-8 spring.thymeleaf.content-type=text/html spring.thymeleaf.cache=false </pre></td> 
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test.html

Controller

启动demo

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 <td><pre>1 2 3 4 5 6 7 </pre></td> 
 <td><pre> @SpringBootApplication(scanBasePackages="cn.shiyujun.controller") public class MVCDemo { public static void main (String args[]){
 SpringApplication.run(MVCDemo.class, args); } } </pre></td> 
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至此Deno工程搭建完毕，有需要源码的同学可以从下方地址获取  
https://github.com/shiyujun/spring-framework

#### 源码分析 ####

##### SpringMVC自动配置 #####

我们知道在SpringBoot中使用SpringMVC的时候是不需要像传统Spring中配置web.xml和配置文件等等的。那么大家知道这是为什么吗

答案就在这个类`WebMvcAutoConfiguration`里面

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 <td><pre>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 </pre></td> 
 <td><pre> @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 { 	public static final String DEFAULT_PREFIX = ""; 	public static final String DEFAULT_SUFFIX = ""; 	private static final String[] SERVLET_LOCATIONS = { "/" }; 	@Bean 	@ConditionalOnMissingBean(HiddenHttpMethodFilter.class) 	public OrderedHiddenHttpMethodFilter hiddenHttpMethodFilter() {
 		return new OrderedHiddenHttpMethodFilter(); 	} 	@Bean 	@ConditionalOnMissingBean(HttpPutFormContentFilter.class) 	@ConditionalOnProperty(prefix = "spring.mvc.formcontent.putfilter", name = "enabled", matchIfMissing = true) 	public OrderedHttpPutFormContentFilter httpPutFormContentFilter() {
 		return new OrderedHttpPutFormContentFilter(); 	} 	@Configuration 	@Import(EnableWebMvcConfiguration.class) 	@EnableConfigurationProperties({ WebMvcProperties.class, ResourceProperties.class }) 	public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer, ResourceLoaderAware { 		@Bean 		@ConditionalOnMissingBean 		public InternalResourceViewResolver defaultViewResolver() {
 			InternalResourceViewResolver resolver = new InternalResourceViewResolver(); 			resolver.setPrefix(this.mvcProperties.getView().getPrefix()); 			resolver.setSuffix(this.mvcProperties.getView().getSuffix()); 			return resolver; 		} 		@Bean 		@ConditionalOnBean(View.class) 		@ConditionalOnMissingBean 		public BeanNameViewResolver beanNameViewResolver() {
 			BeanNameViewResolver resolver = new BeanNameViewResolver(); 			resolver.setOrder(Ordered.LOWEST_PRECEDENCE - 10); 			return resolver; 		} 		@Bean 		@ConditionalOnBean(ViewResolver.class) 		@ConditionalOnMissingBean(name = "viewResolver", value = ContentNegotiatingViewResolver.class) 		public ContentNegotiatingViewResolver viewResolver(BeanFactory beanFactory) {
 			ContentNegotiatingViewResolver resolver = new ContentNegotiatingViewResolver(); 			resolver.setContentNegotiationManager( 					beanFactory.getBean(ContentNegotiationManager.class)); 			// ContentNegotiatingViewResolver uses all the other view resolvers to locate 			// a view so it should have a high precedence 			resolver.setOrder(Ordered.HIGHEST_PRECEDENCE); 			return resolver; 		} 		@Bean 		@ConditionalOnMissingBean 		@ConditionalOnProperty(prefix = "spring.mvc", name = "locale") 		public LocaleResolver localeResolver() {
 			if (this.mvcProperties 					.getLocaleResolver() == WebMvcProperties.LocaleResolver.FIXED) {
 				return new FixedLocaleResolver(this.mvcProperties.getLocale()); 			} 			AcceptHeaderLocaleResolver localeResolver = new AcceptHeaderLocaleResolver(); 			localeResolver.setDefaultLocale(this.mvcProperties.getLocale()); 			return localeResolver; 		} 		@Bean 		public WelcomePageHandlerMapping welcomePageHandlerMapping( 				ApplicationContext applicationContext) {
 			return new WelcomePageHandlerMapping( 					new TemplateAvailabilityProviders(applicationContext), 					applicationContext, getWelcomePage(), 					this.mvcProperties.getStaticPathPattern()); 		} 		@Bean 		@ConditionalOnMissingBean({ RequestContextListener.class, 				RequestContextFilter.class }) 		public static RequestContextFilter requestContextFilter() {
 			return new OrderedRequestContextFilter(); 		} 		@Configuration 		@ConditionalOnProperty(value = "spring.mvc.favicon.enabled", matchIfMissing = true) 		public static class FaviconConfiguration implements ResourceLoaderAware { 			@Bean 			public SimpleUrlHandlerMapping faviconHandlerMapping() {
 				SimpleUrlHandlerMapping mapping = new SimpleUrlHandlerMapping(); 				mapping.setOrder(Ordered.HIGHEST_PRECEDENCE + 1); 				mapping.setUrlMap(Collections.singletonMap("**/favicon.ico", 						faviconRequestHandler())); 				return mapping; 			} 			@Bean 			public ResourceHttpRequestHandler faviconRequestHandler() {
 				ResourceHttpRequestHandler requestHandler = new ResourceHttpRequestHandler(); 				requestHandler.setLocations(resolveFaviconLocations()); 				return requestHandler; 			} 		} 	} 	/** * Configuration equivalent to { @code @EnableWebMvc}. */ 	@Configuration 	public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration { 		@Bean 		@Override 		public RequestMappingHandlerAdapter requestMappingHandlerAdapter() {
 			RequestMappingHandlerAdapter adapter = super.requestMappingHandlerAdapter(); 			adapter.setIgnoreDefaultModelOnRedirect(this.mvcProperties == null 					|| this.mvcProperties.isIgnoreDefaultModelOnRedirect()); 			return adapter; 		} 		@Bean 		@Primary 		@Override 		public RequestMappingHandlerMapping requestMappingHandlerMapping() {
 			// Must be @Primary for MvcUriComponentsBuilder to work 			return super.requestMappingHandlerMapping(); 		} 		@Bean 		@Override 		public FormattingConversionService mvcConversionService() {
 			WebConversionService conversionService = new WebConversionService( 					this.mvcProperties.getDateFormat()); 			addFormatters(conversionService); 			return conversionService; 		} 		@Bean 		@Override 		public Validator mvcValidator() {
 			if (!ClassUtils.isPresent("javax.validation.Validator", 					getClass().getClassLoader())) {
 				return super.mvcValidator(); 			} 			return ValidatorAdapter.get(getApplicationContext(), getValidator()); 		} 		@Bean 		@Override 		public ContentNegotiationManager mvcContentNegotiationManager() {
 			ContentNegotiationManager manager = super.mvcContentNegotiationManager(); 			List&lt;ContentNegotiationStrategy&gt; strategies = manager.getStrategies(); 			ListIterator&lt;ContentNegotiationStrategy&gt; iterator = strategies.listIterator(); 			while (iterator.hasNext()) {
 				ContentNegotiationStrategy strategy = iterator.next(); 				if (strategy instanceof PathExtensionContentNegotiationStrategy) {
 					iterator.set(new OptionalPathExtensionContentNegotiationStrategy( 							strategy)); 				} 			} 			return manager; 		} 	} 	@Configuration 	@ConditionalOnEnabledResourceChain 	static class ResourceChainCustomizerConfiguration { 		@Bean 		public ResourceChainResourceHandlerRegistrationCustomizer resourceHandlerRegistrationCustomizer() {
 			return new ResourceChainResourceHandlerRegistrationCustomizer(); 		} 	} } </pre></td> 
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仔细看这个类，你就会发现这些自动注入的一些类都是之前需要我们在xml文件中配置的，只不过是SpringBoot帮我们做了这个操作。只有当我们需要自定义一些东西的才有必要去关心这些配置，平常使用的时候拿来就用即可。这就是大名鼎鼎的约定大于配置

##### 初始化`DispatcherServlet` #####

`DispatcherServlet`是一个实现了`Servlet`接口的类，`Servlet`的初始化阶段会调用它的`init()`方法，而`DispatcherServlet`的方法是继承自父类`HttpServletBean`的

初始化web容器

下面会看到一些熟悉的东西

可以看到上方这一块代码都是一些常用组件的初始化，初始化的逻辑都比较简单，下面随意挑取2个看一下

至此，`DispatcherServlet`的初始化就完成了

![640?wx\_fmt=png][640_wx_fmt_png]

[640_wx_fmt_png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/84878364145b4bc682a911bd6c753233.png