SpringMVC源码解析（一）
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
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.0.RELEASE</version>
</parent>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>application.properties
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=falsetest.html
<!DOCTYPE HTML>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org">
<head>
<meta content="text/html;charset=UTF-8"/>
</head>
<body>
<span th:text="'用户名：'+${name}+',年龄：'+${age}">
</span>
</body>
</html>Controller
@Controller
public class MVCDemoController {
@RequestMapping(value = "/testMVC",method = RequestMethod.GET )
public String testMVC(Model model){
model.addAttribute("name","张三");
model.addAttribute("age","18");
return "test";
}
}启动demo
@SpringBootApplication(scanBasePackages="cn.shiyujun.controller")
public class MVCDemo {
public static void main (String args[]){
SpringApplication.run(MVCDemo.class, args);
}
}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
@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<ContentNegotiationStrategy> strategies = manager.getStrategies();
ListIterator<ContentNegotiationStrategy> 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();
}
}
}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
public final void init() throws ServletException {
if (logger.isDebugEnabled()) {
logger.debug("Initializing servlet '" + getServletName() + "'");
}
//处理init-param参数，但是SpringBoot中默认是没有的
PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
if (!pvs.isEmpty()) {
try {
BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
initBeanWrapper(bw);
bw.setPropertyValues(pvs, true);
}
catch (BeansException ex) {
if (logger.isErrorEnabled()) {
logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
}
throw ex;
}
}
// 初始化Servlet，往下看
initServletBean();
if (logger.isDebugEnabled()) {
logger.debug("Servlet '" + getServletName() + "' configured successfully");
}
}
protected final void initServletBean() throws ServletException {
getServletContext().log("Initializing Spring FrameworkServlet '" + getServletName() + "'");
if (this.logger.isInfoEnabled()) {
this.logger.info("FrameworkServlet '" + getServletName() + "': initialization started");
}
long startTime = System.currentTimeMillis();
try {
//初始化web容器
this.webApplicationContext = initWebApplicationContext();
//扩展点
initFrameworkServlet();
}
catch (ServletException ex) {
this.logger.error("Context initialization failed", ex);
throw ex;
}
catch (RuntimeException ex) {
this.logger.error("Context initialization failed", ex);
throw ex;
}
if (this.logger.isInfoEnabled()) {
long elapsedTime = System.currentTimeMillis() - startTime;
this.logger.info("FrameworkServlet '" + getServletName() + "': initialization completed in " +
elapsedTime + " ms");
}
}初始化web容器
protected WebApplicationContext initWebApplicationContext() {
//获取AnnotationConfigServletWebServerApplicationContext类型的web容器
WebApplicationContext rootContext =
WebApplicationContextUtils.getWebApplicationContext(getServletContext());
WebApplicationContext wac = null;
if (this.webApplicationContext != null) {
wac = this.webApplicationContext;
if (wac instanceof ConfigurableWebApplicationContext) {
ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
if (!cwac.isActive()) {
if (cwac.getParent() == null) {
cwac.setParent(rootContext);
}
configureAndRefreshWebApplicationContext(cwac);
}
}
}
if (wac == null) {
wac = findWebApplicationContext();
}
if (wac == null) {
wac = createWebApplicationContext(rootContext);
}
if (!this.refreshEventReceived) {
// 刷新应用上下文，这里是重点，接着往下看
onRefresh(wac);
}
if (this.publishContext) {
// 推送事件通知
String attrName = getServletContextAttributeName();
getServletContext().setAttribute(attrName, wac);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Published WebApplicationContext of servlet '" + getServletName() +
"' as ServletContext attribute with name [" + attrName + "]");
}
}
return wac;
}下面会看到一些熟悉的东西
protected void onRefresh(ApplicationContext context) {
initStrategies(context);
}
protected void initStrategies(ApplicationContext context) {
initMultipartResolver(context);
initLocaleResolver(context);
initThemeResolver(context);
initHandlerMappings(context);
initHandlerAdapters(context);
initHandlerExceptionResolvers(context);
initRequestToViewNameTranslator(context);
initViewResolvers(context);
initFlashMapManager(context);
}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
private void initMultipartResolver(ApplicationContext context) {
try {
this.multipartResolver = context.getBean(MULTIPART_RESOLVER_BEAN_NAME, MultipartResolver.class);
if (logger.isDebugEnabled()) {
logger.debug("Using MultipartResolver [" + this.multipartResolver + "]");
}
}
catch (NoSuchBeanDefinitionException ex) {
// Default is no multipart resolver.
this.multipartResolver = null;
if (logger.isDebugEnabled()) {
logger.debug("Unable to locate MultipartResolver with name '" + MULTIPART_RESOLVER_BEAN_NAME +
"': no multipart request handling provided");
}
}
}
private void initHandlerMappings(ApplicationContext context) {
this.handlerMappings = null;
if (this.detectAllHandlerMappings) {
// 加载所有实现HandlerMapping接口的bean
Map<String, HandlerMapping> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerMappings = new ArrayList<>(matchingBeans.values());
// 排序，Spring处理请求就是根据这个排序的结果进行处理，如果当前handlerMapping不可以处理则抛给下一个
AnnotationAwareOrderComparator.sort(this.handlerMappings);
}
}
else {
try {
HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);
this.handlerMappings = Collections.singletonList(hm);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, we'll add a default HandlerMapping later.
}
}
// Ensure we have at least one HandlerMapping, by registering
// a default HandlerMapping if no other mappings are found.
if (this.handlerMappings == null) {
this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
if (logger.isDebugEnabled()) {
logger.debug("No HandlerMappings found in servlet '" + getServletName() + "': using default");
}
}
}至此，DispatcherServlet的初始化就完成了
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原始发表：2019-09-04，如有侵权请联系 cloudcommunity@tencent.com 删除
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