SpringBoot | SpringBoot Web开发

public void addResourceHandlers(ResourceHandlerRegistry registry) {
    if (!this.resourceProperties.isAddMappings()) {
        // 已禁用默认资源处理
        logger.debug("Default resource handling disabled");
    } else {
        // 缓存处理
        Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
        CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();
        // webjars配置
        if (!registry.hasMappingForPattern("/webjars/**")) {
            this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]{"/webjars/**"}).addResourceLocations(new String[]{"classpath:/META-INF/resources/webjars/"}).setCachePeriod(this.getSeconds(cachePeriod)).setCacheControl(cacheControl));
        }

        // 静态资源配置
        String staticPathPattern = this.mvcProperties.getStaticPathPattern();
        if (!registry.hasMappingForPattern(staticPathPattern)) {
            this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]{staticPathPattern}).addResourceLocations(WebMvcAutoConfiguration.getResourceLocations(this.resourceProperties.getStaticLocations())).setCachePeriod(this.getSeconds(cachePeriod)).setCacheControl(cacheControl));
        }

    }
}

<dependency>
    <groupId>org.webjars</groupId>
    <artifactId>jquery</artifactId>
    <version>3.4.1</version>
</dependency>

public class ResourceProperties {
    // 找到对应路径
    private static final String[] CLASSPATH_RESOURCE_LOCATIONS = new String[]{"classpath:/META-INF/resources/", "classpath:/resources/", "classpath:/static/", "classpath:/public/"};
    private String[] staticLocations;
    private boolean addMappings;
    private final ResourceProperties.Chain chain;
    private final ResourceProperties.Cache cache;

    public ResourceProperties() {
        // 找到对应的值
        this.staticLocations = CLASSPATH_RESOURCE_LOCATIONS;
        this.addMappings = true;
        this.chain = new ResourceProperties.Chain();
        this.cache = new ResourceProperties.Cache();
    }

    // 进入方法
    public String[] getStaticLocations() {
        return this.staticLocations;
    }
    
    ......
}

  this.resourceProperties = webProperties.getResources();

"classpath:/META-INF/resources/"
"classpath:/resources/"
"classpath:/static/"
"classpath:/public/"

spring.web.resources.static-locations=classpath:/BoBooY/,classpath:/BoBooY2/

@Bean
public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext, FormattingConversionService mvcConversionService, ResourceUrlProvider mvcResourceUrlProvider) {
    // getWelcomePage 获得欢迎页
    WelcomePageHandlerMapping welcomePageHandlerMapping = new WelcomePageHandlerMapping(new TemplateAvailabilityProviders(applicationContext), applicationContext, this.getWelcomePage(), this.mvcProperties.getStaticPathPattern());
    welcomePageHandlerMapping.setInterceptors(this.getInterceptors(mvcConversionService, mvcResourceUrlProvider));
    welcomePageHandlerMapping.setCorsConfigurations(this.getCorsConfigurations());
    return welcomePageHandlerMapping;
}

private Optional<Resource> getWelcomePage() {
    String[] locations = WebMvcAutoConfiguration.getResourceLocations(this.resourceProperties.getStaticLocations());
    // ::是java8 中新引入的运算符
	// Class::function的时候function是属于Class的，应该是静态方法。
	// this::function的funtion是属于这个对象的。
	// 简而言之，就是一种语法糖而已，是一种简写
    return Arrays.stream(locations).map(this::getIndexHtml).filter(this::isReadable).findFirst();
}

// 欢迎页就是一个location下的的 index.html 而已
private Resource getIndexHtml(String location) {
    return this.resourceLoader.getResource(location + "index.html");
}

"classpath:/resources/"
"classpath:/static/"
"classpath:/public/"

# 关闭默认图标
spring.mvc.favicon.enabled=false

<!--thymeleaf-->
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>

@ConfigurationProperties(
    prefix = "spring.thymeleaf"
)
public class ThymeleafProperties {
    private static final Charset DEFAULT_ENCODING;
    public static final String DEFAULT_PREFIX = "classpath:/templates/";
    public static final String DEFAULT_SUFFIX = ".html";
    private boolean checkTemplate = true;
    private boolean checkTemplateLocation = true;
    private String prefix = "classpath:/templates/";
    private String suffix = ".html";
    private String mode = "HTML";
    private Charset encoding;
    private boolean cache;
    private Integer templateResolverOrder;
    private String[] viewNames;
    private String[] excludedViewNames;
    private boolean enableSpringElCompiler;
    private boolean renderHiddenMarkersBeforeCheckboxes;
    private boolean enabled;
    private final ThymeleafProperties.Servlet servlet;
    private final ThymeleafProperties.Reactive reactive;
}

@Controller
public class HelloController {
    @RequestMapping("/hello")
    public String hello(Model model) {
        return "hello";
    }
}

<!DOCTYPE html>
<html lang="en" >
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <p>hello world!</p>
</body>
</html>

@Controller
public class HelloController {
    @RequestMapping("/hello")
    public String hello(Model model) {
        model.addAttribute("msg","这是一个测试");
        return "hello";
    }
}

<html xmlns:th="http://www.thymeleaf.org">

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>测试</title>
</head>
<body>

  <h1>测试页</h1>
  <!-- 所有的html元素都可以被thymeleaf替换接管： th:元素名
  th:text就是将div中的内容设置为它指定的值 -->
  <div th:text="${msg}"></div>

</body>
</html>

Simple expressions:（表达式语法）
Variable Expressions: ${...}：获取变量值；OGNL；
  1）、获取对象的属性、调用方法
  2）、使用内置的基本对象： #18
      #ctx : the context object.
      #vars: the context variables.
      #locale : the context locale.
      #request : (only in Web Contexts) the HttpServletRequest object.
      #response : (only in Web Contexts) the HttpServletResponse object.
      #session : (only in Web Contexts) the HttpSession object.
      #servletContext : (only in Web Contexts) the ServletContext object.
  3）、内置的一些工具对象：
      #execInfo : information about the template being processed.
      #uris : methods for escaping parts of URLs/URIs
      #conversions : methods for executing the configured conversion
  service (if any).
  	  #dates : methods for java.util.Date objects: formatting, component
  extraction, etc.
  	  #calendars : analogous to #dates , but for java.util.Calendar
  objects.
      #numbers : methods for formatting numeric objects.
      #strings : methods for String objects: contains, startsWith,
  prepending/appending, etc.
      #objects : methods for objects in general.
      #bools : methods for boolean evaluation.
      #arrays : methods for arrays.
      #lists : methods for lists.
      #sets : methods for sets.
      #maps : methods for maps.
      #aggregates : methods for creating aggregates on arrays or
  collections.
  ============================================================================
  ======
          
      Selection Variable Expressions: *{...}：选择表达式：和${}在功能上是一样；
      Message Expressions: #{...}：获取国际化内容
      Link URL Expressions: @{...}：定义URL；
      Fragment Expressions: ~{...}：片段引用表达式
  Literals（字面量）
      Text literals: 'one text' , 'Another one!' ,…
      Number literals: 0 , 34 , 3.0 , 12.3 ,…
      Boolean literals: true , false
      Null literal: null
      Literal tokens: one , sometext , main ,…
  Text operations:（文本操作）
      String concatenation: +
      Literal substitutions: |The name is ${name}|
  Arithmetic operations:（数学运算）
      Binary operators: + , - , * , / , %
      Minus sign (unary operator): -
  Boolean operations:（布尔运算）
      Binary operators: and , or
      Boolean negation (unary operator): ! , not
  Comparisons and equality:（比较运算）
      Comparators: > , < , >= , <= ( gt , lt , ge , le )
	  Equality operators: == , != ( eq , ne )
  Conditional operators:条件运算（三元运算符）
      If-then: (if) ? (then)
      If-then-else: (if) ? (then) : (else)
      Default: (value) ?: (defaultvalue)
  Special tokens:
  	  No-Operation: _

@Controller
public class TestController {
    @RequestMapping("/test")
    public String test(Model model, Map<String,Object> map) {
        model.addAttribute("msg", "<h1>BoBooY</h1>");
        map.put("users", Arrays.asList("BoBooY","test"));
        return "test";
    }
}

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <!-- 所有的html元素都可以被thymeleaf替换接管： th:元素名
 th:text就是将div中的内容设置为它指定的值 -->
    <div th:text="${msg}"></div>
    <!--  不转义  -->
    <div th:utext="${msg}"></div>
    <!--遍历数据-->
    <!--th:each每次遍历都会生成当前这个标签：官网#9-->
    <ul>
        <li th:each="user:${users}" th:text="${user}"></li>
    </ul>
</body>
</html>

Spring MVC Auto-configuration
// Spring Boot为Spring MVC提供了自动配置，它可以很好地与大多数应用程序一起工作。
Spring Boot provides auto-configuration for Spring MVC that works well with most applications.
// 自动配置在Spring默认设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:
// 包含视图解析器
Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.
// 支持静态资源文件夹的路径，以及webjars
Support for serving static resources, including support for WebJars 
// 自动注册了Converter：
// 转换器，这就是我们网页提交数据到后台自动封装成为对象的东西，比如把"1"字符串自动转换为int类型
// Formatter：【格式化器，比如页面给我们了一个2019-8-10，它会给我们自动格式化为Date对象】
Automatic registration of Converter, GenericConverter, and Formatter beans.
// HttpMessageConverters
// SpringMVC用来转换Http请求和响应的的，比如我们要把一个User对象转换为JSON字符串，可以去看官网文档解释；
Support for HttpMessageConverters (covered later in this document).
// 定义错误代码生成规则的
Automatic registration of MessageCodesResolver (covered later in this document).
// 首页定制
Static index.html support.
// 图标定制
Custom Favicon support (covered later in this document).
// 初始化数据绑定器：帮我们把请求数据绑定到JavaBean中！
Automatic use of a ConfigurableWebBindingInitializer bean (covered later in this document).

/*
如果您希望保留Spring Boot MVC功能，并且希望添加其他MVC配置（拦截器、格式化程序、视图控制器和其他功能），则可以添加自己
的@configuration类，类型为webmvcconfiguer，但不添加@EnableWebMvc。如果希望提供
RequestMappingHandlerMapping、RequestMappingHandlerAdapter或ExceptionHandlerExceptionResolver的自定义
实例，则可以声明WebMVCregistrationAdapter实例来提供此类组件。
*/
If you want to keep Spring Boot MVC features and you want to add additional MVC configuration 
(interceptors, formatters, view controllers, and other features), you can add your own 
@Configuration class of type WebMvcConfigurer but without @EnableWebMvc. If you wish to provide 
custom instances of RequestMappingHandlerMapping, RequestMappingHandlerAdapter, or 
ExceptionHandlerExceptionResolver, you can declare a WebMvcRegistrationsAdapter instance to provide such components.

// 如果您想完全控制Spring MVC，可以添加自己的@Configuration，并用@EnableWebMvc进行注释。
If you want to take complete control of Spring MVC, you can add your own @Configuration annotated with @EnableWebMvc.

@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使用所有其他视图解析器来定位视图，因此它应该具有较高的优先级
    resolver.setOrder(Ordered.HIGHEST_PRECEDENCE);
    return resolver;
}

@Nullable // 注解说明：@Nullable 即参数可为null
public View resolveViewName(String viewName, Locale locale) throws Exception {
    RequestAttributes attrs = RequestContextHolder.getRequestAttributes();
    Assert.state(attrs instanceof ServletRequestAttributes, "No current ServletRequestAttributes");
    List<MediaType> requestedMediaTypes = this.getMediaTypes(((ServletRequestAttributes)attrs).getRequest());
    if (requestedMediaTypes != null) {
        // 获取候选的视图对象
        List<View> candidateViews = this.getCandidateViews(viewName, locale, requestedMediaTypes);
        // 选择一个最适合的视图对象，然后把这个对象返回
        View bestView = this.getBestView(candidateViews, requestedMediaTypes, attrs);
        if (bestView != null) {
            return bestView;
        }
    }

    String mediaTypeInfo = this.logger.isDebugEnabled() && requestedMediaTypes != null ? " given " + requestedMediaTypes.toString() : "";
    if (this.useNotAcceptableStatusCode) {
        if (this.logger.isDebugEnabled()) {
            this.logger.debug("Using 406 NOT_ACCEPTABLE" + mediaTypeInfo);
        }

        return NOT_ACCEPTABLE_VIEW;
    } else {
        this.logger.debug("View remains unresolved" + mediaTypeInfo);
        return null;
    }
}

Iterator var5 = this.viewResolvers.iterator();

protected void initServletContext(ServletContext servletContext) {
    // 这里它是从beanFactory工具中获取容器中的所有视图解析器
    // ViewRescolver.class 把所有的视图解析器来组合的
    Collection<ViewResolver> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(this.obtainApplicationContext(), ViewResolver.class).values();
    ViewResolver viewResolver;
    if (this.viewResolvers == null) {
        this.viewResolvers = new ArrayList(matchingBeans.size());
    }
    // ...............
}

@Bean // 放到bean中
public ViewResolver myViewResolver(){
    return new MyViewResolver();
}

// 写一个静态内部类，视图解析器就需要实现ViewResolver接口
private static class MyViewResolver implements ViewResolver{
    @Override
    public View resolveViewName(String s, Locale locale) throws Exception {
        return null;
    }
}

@Bean
@Override
public FormattingConversionService mvcConversionService() {
    Format format = this.mvcProperties.getFormat();
    WebConversionService conversionService = new WebConversionService(new DateTimeFormatters().dateFormat(format.getDate()).timeFormat(format.getTime()).dateTimeFormat(format.getDateTime()));
    addFormatters(conversionService);
    return conversionService;
}

public String getDateFormat() {
    return this.dateFormat;
}

public void setDateFormat(String dateFormat) {
    this.dateFormat = dateFormat;
}

// Date format to use. For instance, `dd/MM/yyyy`. 默认的
private String dateFormat;

If you want to keep Spring Boot MVC features and you want to add additional MVC configuration (interceptors, formatters, view controllers, and other features), you can add your own @Configuration class of type WebMvcConfigurer but without @EnableWebMvc. If you wish to provide custom instances of RequestMappingHandlerMapping, RequestMappingHandlerAdapter, or ExceptionHandlerExceptionResolver, you can declare a WebMvcRegistrationsAdapter instance to provide such components.

// 扩展springmvc Dispacherservle
//可以使用自定义类扩展MVC的功能
@Configuration
public class MyMvcConfig implements WebMvcConfigurer {

    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        // 浏览器发送/test ， 就会跳转到test页面；
        registry.addViewController("/test").setViewName("test");
    }
}

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org/">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
这是一个测试MyMvcConfig的页面
</body>
</html>

@Configuration
public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {
    private final WebMvcConfigurerComposite configurers = new WebMvcConfigurerComposite();

    public DelegatingWebMvcConfiguration() {
    }

    // 从容器中获取所有的webmvcConfigurer
    @Autowired(
        required = false
    )
    public void setConfigurers(List<WebMvcConfigurer> configurers) {
        if (!CollectionUtils.isEmpty(configurers)) {
            this.configurers.addWebMvcConfigurers(configurers);
        }

    }
}

public void addWebMvcConfigurers(List<WebMvcConfigurer> configurers) {
    if (!CollectionUtils.isEmpty(configurers)) {
        this.delegates.addAll(configurers);
    }

}

public void addFormatters(FormatterRegistry registry) {
    Iterator var2 = this.delegates.iterator();

    while(var2.hasNext()) {
        // 将所有的WebMvcConfigurer相关配置来一起调用！包括我们自己配置的和Spring给我们配置的
        WebMvcConfigurer delegate = (WebMvcConfigurer)var2.next();
        delegate.addFormatters(registry);
    }

}

If you want to take complete control of Spring MVC
you can add your own @Configuration annotated with @EnableWebMvc.

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

@Configuration
public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {
    private final WebMvcConfigurerComposite configurers = new WebMvcConfigurerComposite();
.......
}

@Configuration
@ConditionalOnWebApplication(
    type = Type.SERVLET
)
@ConditionalOnClass({Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class})
// 容器中没有这个组件的时候，这个自动配置类才生效
@ConditionalOnMissingBean({WebMvcConfigurationSupport.class})
@AutoConfigureOrder(-2147483638)
@AutoConfigureAfter({DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class, ValidationAutoConfiguration.class})
public class WebMvcAutoConfiguration {
    public static final String DEFAULT_PREFIX = "";
    public static final String DEFAULT_SUFFIX = "";
    private static final String[] SERVLET_LOCATIONS = new String[]{"/"};

    public WebMvcAutoConfiguration() {
    }
    ......
}