飞天班第10节：SpringBoot开发单体应用（上）

@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
  // 默认规则的配置被禁用，如果你手动添加了资源映射路径的配置，那么这些自动配置就会直接失效
  if (!this.resourceProperties.isAddMappings()) {
    logger.debug("Default resource handling disabled");
    return;
  }
  // 下面是自动配置
  // 缓存控制
  Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
  CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();
  // 分析源代码，需要掌握看对象的方法调用，上面两行代码只是获取对象，我们要看对象怎么用
  
  // 第一种策略 /webjars/**
  // 判断注册器是否存在一个映射路径 /webjars/**，有的话就绑定资源路径，并配置到缓存中
  // addResourceHandler 处理逻辑，如 /webjars/a.js
  // addResourceLocations 处理资源的地址，如 /classpath:/META-INF/resources/webjars/a.js
  if (!registry.hasMappingForPattern("/webjars/**")) {
    customizeResourceHandlerRegistration(registry.addResourceHandler("/webjars/**")
                                         .addResourceLocations("classpath:/META-INF/resources/webjars/")
                                         .setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
  }
  // 第二种策略 /**
  // 获取静态资源路径，进行映射并放入缓存中
  String staticPathPattern = this.mvcProperties.getStaticPathPattern();
  if (!registry.hasMappingForPattern(staticPathPattern)) {
    customizeResourceHandlerRegistration(registry.addResourceHandler(staticPathPattern)
                                         .addResourceLocations(getResourceLocations(this.resourceProperties.getStaticLocations()))
                                         .setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
  }
}

private static final String[] CLASSPATH_RESOURCE_LOCATIONS = 
{ 
  "classpath:/META-INF/resources/", // 优先级最高,在starter 中使用，如swagger-ui，spirng.factories文件
   "classpath:/resources/",   // 文件资源 
  "classpath:/static/",  // 静态资源
  "classpath:/public/"  // 公共的，如图标等
};

/META-INF/resources 优先级最高，依次是 resources,static,public

// 默认规则的配置被禁用，如果你手动添加了资源映射路径的配置，那么这些自动配置就会直接失效
  if (!this.resourceProperties.isAddMappings()) {
    logger.debug("Default resource handling disabled");
    return;
  }

// 首页会被映射到这个处理器下
@Bean
public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext,
                                                           FormattingConversionService mvcConversionService, ResourceUrlProvider mvcResourceUrlProvider) {
  WelcomePageHandlerMapping welcomePageHandlerMapping = new WelcomePageHandlerMapping(
    new TemplateAvailabilityProviders(applicationContext), applicationContext, getWelcomePage(),
    this.mvcProperties.getStaticPathPattern());
  welcomePageHandlerMapping.setInterceptors(getInterceptors(mvcConversionService, mvcResourceUrlProvider));
  return welcomePageHandlerMapping;
}

// 获得欢迎页
private Optional<Resource> getWelcomePage() {
  // 4个静态路径目录
  String[] locations = getResourceLocations(this.resourceProperties.getStaticLocations());
  // stream流
  // map 映射
  // filter 过滤
  // findFirst 找到第一个符号条件的
  // 调用对象方法的语法糖, this 对象:: getIndexHtml 方法名字
  return Arrays.stream(locations).map(this::getIndexHtml).filter(this::isReadable).findFirst();
}

private Resource getIndexHtml(String location) {
  return this.resourceLoader.getResource(location + "index.html");
}

WelcomePageHandlerMapping(TemplateAvailabilityProviders templateAvailabilityProviders,
                          ApplicationContext applicationContext, Optional<Resource> welcomePage, String staticPathPattern) {
  if (welcomePage.isPresent() && "/**".equals(staticPathPattern)) {
    logger.info("Adding welcome page: " + welcomePage.get());
    setRootViewName("forward:index.html");
  }
  else if (welcomeTemplateExists(templateAvailabilityProviders, applicationContext)) {
    logger.info("Adding welcome page template: index");
    setRootViewName("index");
  }
}

private static final String[] CLASSPATH_RESOURCE_LOCATIONS = { "classpath:/META-INF/resources/","classpath:/resources/", "classpath:/static/", "classpath:/public/" };

@ConfigurationProperties(prefix = "spring.thymeleaf")
public class ThymeleafProperties {

	private static final Charset DEFAULT_ENCODING = StandardCharsets.UTF_8;

  // 默认前缀
	public static final String DEFAULT_PREFIX = "classpath:/templates/";
// 默认后缀
	public static final String DEFAULT_SUFFIX = ".html";

	/**
	 * Whether to check that the template exists before rendering it.
	 */
	private boolean checkTemplate = true;

	/**
	 * Whether to check that the templates location exists.
	 */
	private boolean checkTemplateLocation = true;
  ...

@Controller
public class IndexController {
  @GetMapping("test")
  public static test(Model model){
    model.addAttribute("msg","hello,Thymeleaf");
    return "home"; // 看上面的ThymeleafProperties,不修改前缀后缀的话，跳转到
    // classpath:/templates/test.html页面
  }
  
}

@Controller
public class IndexController {
  @GetMapping("test")
  public static test(Model model){
    model.addAttribute("msg","hello,Thymeleaf");
    model.addAttribute("msg2","<h1>hello,Thymeleaf</h1>");
    model.addAttribute("users",Arrays.asList("coding,qinjiang"));
    return "home"; // 看上面的ThymeleafProperties,不修改前缀后缀的话，跳转到
    // classpath:/templates/test.html页面
  }
}

${#messages.msg('msgKey')} 
${#uris.escapePath(uri)} 
${#conversions.convert(object, 'java.util.TimeZone')} 转换
// See javadoc API for class org.thymeleaf.expression.Dates 
${#dates.format(date, 'dd/MMM/yyyy HH:mm')} 日期格式化
${#calendars.format(cal)} calendars对象
${#numbers.formatInteger(num,3)} 
${#strings.toString(obj)} 
${#arrays.toArray(object)}

Spring MVC Auto-configuration
// Springboot 为 spring mvc 提供了自动配置,很好的工作与大多数应用
Spring Boot provides auto-configuration for Spring MVC that works well with most applications.
// 自动配置在Spring默认配置的基础上添加了以下功能
The auto-configuration adds the following features on top of Spring’s defaults:
// 包含了内容导航视图解析器和bean名称视图解析器
Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.
// 支持静态资源文件路径映射，包含webjars的支持 
Support for serving static resources, including support for WebJars (covered later in this document)).
// 自动注册转换器，通用转换器和格式化器
  // 例如网页提交的前端对象，到后台自动封装为具体的对象；字符串 “1” 转换为数字1，都是转换器在工作；时间字符串2020-03-18 到后台能转换为Date类型，则是Formatter bean在工作，Springbooot默认引入jackjson 配置时间格式
Automatic registration of Converter, GenericConverter, and Formatter beans.
// 支持Http消息转换，如request\response 对象自动转换为json对象
Support for HttpMessageConverters (covered later in this document).
// 自动注册消息代码解析
Automatic registration of MessageCodesResolver (covered later in this document).
// 支持静态首页定制
Static index.html support.
// 自定义网站图标
Custom Favicon support (covered later in this document).
// 自动配置web数据绑定
Automatic use of a ConfigurableWebBindingInitializer bean (covered later in this document).

// 如果你想保持Springboot 对MVC的自动配置基础上，做更多的自定义配置，如拦截器、格式化器，视图控制，你可以在自定义配置类（类型为WebMvcConfigurer），并加上注解 @Configuration ，但是不要加@EnableWebMvc注解
If you want to keep those Spring Boot MVC customizations and make more MVC customizations (interceptors, formatters, view controllers, and other features), you can add your own @Configuration class of type WebMvcConfigurer but without @EnableWebMvc.

// 如果您想自定义request请求映射路由，或者自定义异常解析，你可以声明一个WebMvcRegistrations的bean,
If you want to provide custom instances of RequestMappingHandlerMapping, RequestMappingHandlerAdapter, or ExceptionHandlerExceptionResolver, and still keep the Spring Boot MVC customizations, you can declare a bean of type WebMvcRegistrations and use it to provide custom instances of those components.

// 如果你想完全控制Spring MVC,你可以在自定义配置类上加上@EnableWebMvc注解
If you want to take complete control of Spring MVC, you can add your own @Configuration annotated with @EnableWebMvc, or alternatively add your own @Configuration-annotated DelegatingWebMvcConfiguration as described in the Javadoc of @EnableWebMvc.

@Override
@Nullable // 参数可以为空
public View resolveViewName(String viewName, Locale locale) throws Exception {
  RequestAttributes attrs = RequestContextHolder.getRequestAttributes();
  Assert.state(attrs instanceof ServletRequestAttributes, "No current ServletRequestAttributes");
  List<MediaType> requestedMediaTypes = getMediaTypes(((ServletRequestAttributes) attrs).getRequest());
  if (requestedMediaTypes != null) {
    // 获取所有候选的视图，在分析springboot自动配置的源码时看到过getCandidate这个
    List<View> candidateViews = getCandidateViews(viewName, locale, requestedMediaTypes);
    // 获取最好的视图
    View bestView = getBestView(candidateViews, requestedMediaTypes, attrs);
    if (bestView != null) {
      return bestView; // 返回最好的视图，从所有的视图解析器中获取最好的返回
    }
  }

  String mediaTypeInfo = logger.isDebugEnabled() && requestedMediaTypes != null ?
    " given " + requestedMediaTypes.toString() : "";

  if (this.useNotAcceptableStatusCode) {
    if (logger.isDebugEnabled()) {
      logger.debug("Using 406 NOT_ACCEPTABLE" + mediaTypeInfo);
    }
    return NOT_ACCEPTABLE_VIEW; // 如果没有找到的话，就返回406错误
  }
  else {
    logger.debug("View remains unresolved" + mediaTypeInfo);
    return null;
  }
}

@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;
}

@Configuration
public class MyViewResolverConfig {
	@Bean // 生成一个组件实例放入beanFactory
	public MyViewResolver myViewResolver(){
		return new MyViewResolver();
	}

	private static class MyViewResolver implements ViewResolver{
		@Override
		public View resolveViewName(String viewName, Locale locale) throws Exception {
			return null;
		}
	}
}

@Override
public void addFormatters(FormatterRegistry registry) {
  ApplicationConversionService.addBeans(registry, this.beanFactory);
}

@Bean
@Override // 这是一个服务
public FormattingConversionService mvcConversionService() {
  WebConversionService conversionService = new WebConversionService(this.mvcProperties.getDateFormat());
  addFormatters(conversionService);
  return conversionService;
}

/** 默认的时间格式 / 开头
	 * Date format to use. For instance, `dd/MM/yyyy`.
	 */
private String dateFormat;

// 如果你想保持Springboot 对MVC的自动配置基础上，做更多的自定义配置，如拦截器、格式化器，视图控制，你可以在自定义配置类（类型为WebMvcConfigurer），并加上注解 @Configuration ，但是不要加@EnableWebMvc注解
If you want to keep those Spring Boot MVC customizations and make more MVC customizations (interceptors, formatters, view controllers, and other features), you can add your own @Configuration class of type WebMvcConfigurer but without @EnableWebMvc.
  
// 如果你想完全控制Spring MVC,你可以在自定义配置类上加上@EnableWebMvc注解
If you want to take complete control of Spring MVC, you can add your own @Configuration annotated with @EnableWebMvc, or alternatively add your own @Configuration-annotated DelegatingWebMvcConfiguration as described in the Javadoc of @EnableWebMvc.  

// 自己编写一个视图解析、路由，spring mvc底层就是这么做的
@Configuration
//@EnableWebMvc
public class MyMvcConfig implements WebMvcConfigurer {
    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        // 视图跳转的控制！
        registry.addViewController("/index").setViewName("login");
        registry.addViewController("/").setViewName("login");
        registry.addViewController("/index.html").setViewName("login");
      	registry.addViewController("/test").setViewName("login");
    }
}

@Controller
public class IndexController {
  @RequestMapping({"/test"})
  public String test(){
    return "test";
  }
}

// 如果这个bean不存在，才生效
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)

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

@Configuration
public class MyMvcConfig implements WebMvcConfigurer {

}