【小家Spring】Spring MVC好用工具介绍：UrlPathHelper、WebUtils、RequestContextUtils、WebApplicationContextUtils...(下)

  @Nullable
  public static WebApplicationContext getWebApplicationContext(ServletContext sc) {
    return getWebApplicationContext(sc, WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
  }
  //Required这个方法和上面唯一的区别是：它如果返回null 就直接抛出异常了，上面是返回null
  public static WebApplicationContext getRequiredWebApplicationContext(ServletContext sc) throws IllegalStateException {
    WebApplicationContext wac = getWebApplicationContext(sc);
    if (wac == null) {
      throw new IllegalStateException("No WebApplicationContext found: no ContextLoaderListener registered?");
    }
    return wac;
  }
  // 我在讲解源码的时候：创建容器失败的时候，也会吧异常放进来（我们调用者一般较少使用）
  public static WebApplicationContext getWebApplicationContext(ServletContext sc, String attrName) { ... }
  // 这个可以说是上面的加强版。当getWebApplicationContext(sc)没找到时，还会试从ServletContext的属性中查找唯一的一个WebApplicationContext
  // 如果找到的WebApplicationContext不唯一，则抛出异常声明该情况
  public static WebApplicationContext findWebApplicationContext(ServletContext sc) { ... }
  //向WebApplicationContext使用的BeanFactory注册web有关作用域对象 :
  public static void registerWebApplicationScopes(ConfigurableListableBeanFactory beanFactory,
      @Nullable ServletContext sc) {
    beanFactory.registerScope(WebApplicationContext.SCOPE_REQUEST, new RequestScope());
    beanFactory.registerScope(WebApplicationContext.SCOPE_SESSION, new SessionScope());
    if (sc != null) {
      ServletContextScope appScope = new ServletContextScope(sc);
      beanFactory.registerScope(WebApplicationContext.SCOPE_APPLICATION, appScope);
      // Register as ServletContext attribute, for ContextCleanupListener to detect it.
      // 此处，还吧ServletContext上下文的Scope，注册到上下文里，方便ContextCleanupListener 进行获取
      sc.setAttribute(ServletContextScope.class.getName(), appScope);
    }
    // 定义注入规则。当开发人员依赖注入ServletRequest对象时，注入的bean其实是这里的RequestObjectFactory工厂bean
    beanFactory.registerResolvableDependency(ServletRequest.class, new RequestObjectFactory());
    beanFactory.registerResolvableDependency(ServletResponse.class, new ResponseObjectFactory());
    beanFactory.registerResolvableDependency(HttpSession.class, new SessionObjectFactory());
    // ServletWebRequest 里面既有request，也有response
    beanFactory.registerResolvableDependency(WebRequest.class, new WebRequestObjectFactory());
    if (jsfPresent) {
      FacesDependencyRegistrar.registerFacesDependencies(beanFactory);
    }
  }

  public static void registerEnvironmentBeans(ConfigurableListableBeanFactory bf,
      @Nullable ServletContext servletContext, @Nullable ServletConfig servletConfig) {
    // 把servletContext和servletConfig以Bean的形式，注册到容器里面，这样我们就可以@Autowired了  如下面例子
    if (servletContext != null && !bf.containsBean(WebApplicationContext.SERVLET_CONTEXT_BEAN_NAME)) {
      bf.registerSingleton(WebApplicationContext.SERVLET_CONTEXT_BEAN_NAME, servletContext);
    }
        if (servletConfig != null && !bf.containsBean(ConfigurableWebApplicationContext.SERVLET_CONFIG_BEAN_NAME)) {
      bf.registerSingleton(ConfigurableWebApplicationContext.SERVLET_CONFIG_BEAN_NAME, servletConfig);
    }
    //这个特别特别重要：我们可以看到Spring在启动的时候，把ServletContext里面所有所有的InitParameter都拿出来了，存到一个Map里面
    // 最后把这个Bean注册到容器里面了，Bean名称为：contextParameters
    // 这就是为什么，后面我们可以非常非常方便拿到initParam的原因~~~
    if (!bf.containsBean(WebApplicationContext.CONTEXT_PARAMETERS_BEAN_NAME)) {
      Map<String, String> parameterMap = new HashMap<>();
      if (servletContext != null) {
        Enumeration<?> paramNameEnum = servletContext.getInitParameterNames();
        while (paramNameEnum.hasMoreElements()) {
          String paramName = (String) paramNameEnum.nextElement();
          parameterMap.put(paramName, servletContext.getInitParameter(paramName));
        }
      }
      if (servletConfig != null) {
        Enumeration<?> paramNameEnum = servletConfig.getInitParameterNames();
        while (paramNameEnum.hasMoreElements()) {
          String paramName = (String) paramNameEnum.nextElement();
          parameterMap.put(paramName, servletConfig.getInitParameter(paramName));
        }
      }
      bf.registerSingleton(WebApplicationContext.CONTEXT_PARAMETERS_BEAN_NAME,
          Collections.unmodifiableMap(parameterMap));
    }
    // 原理同上，这里吧ServletContext里面的contextAttributes，都以Bean的形式放进Bean容器里了
    if (!bf.containsBean(WebApplicationContext.CONTEXT_ATTRIBUTES_BEAN_NAME)) {
      Map<String, Object> attributeMap = new HashMap<>();
      if (servletContext != null) {
        Enumeration<?> attrNameEnum = servletContext.getAttributeNames();
        while (attrNameEnum.hasMoreElements()) {
          String attrName = (String) attrNameEnum.nextElement();
          attributeMap.put(attrName, servletContext.getAttribute(attrName));
        }
      }
      bf.registerSingleton(WebApplicationContext.CONTEXT_ATTRIBUTES_BEAN_NAME,
          Collections.unmodifiableMap(attributeMap));
    }
  }

    @Autowired
    private ServletContext servletContext;
    @Autowired
    private ServletConfig servletConfig;
    @ResponseBody
    @GetMapping("/hello")
    public String helloGet() {
        System.out.println(servletContext); //org.apache.catalina.core.StandardWrapperFacade@1f3768f6
        System.out.println(servletConfig); //org.apache.catalina.core.StandardContext$NoPluggabilityServletContext@73ced3c2
        return "hello...Get";
    }

  //将 servletContext、servletConfig 添加到 propertySources
  public static void initServletPropertySources(MutablePropertySources sources,
      @Nullable ServletContext servletContext, @Nullable ServletConfig servletConfig) { ... }

public class UrlPathHelper {
  // 是否总是按照全路径 默认是false（一般不改~） 
  private boolean alwaysUseFullPath = false;
  // 是否对url进行解码（默认都是需要解码的）  解码可以是request.getCharacterEncoding()。若没指定就是下面的defaultEncoding 
  private boolean urlDecode = true;
  // 设置是否应从请求URI中删除“；”（分号）
  private boolean removeSemicolonContent = true;
  // 默认编码是它：ISO-8859-1
  private String defaultEncoding = WebUtils.DEFAULT_CHARACTER_ENCODING;
  ...
}

    @ResponseBody
    @GetMapping("/hello")
    public String helloGet(HttpServletRequest request) throws Exception {
        UrlPathHelper urlPathHelper = new UrlPathHelper();
        System.out.println(urlPathHelper.getLookupPathForRequest(request)); // /api/v1/hello
        System.out.println(urlPathHelper.getOriginatingContextPath(request)); // /demo_war_war
        System.out.println(urlPathHelper.getContextPath(request)); // /demo_war_war
        System.out.println(urlPathHelper.getServletPath(request)); // /api/v1/hello
        System.out.println(urlPathHelper.getRequestUri(request)); // /demo_war_war/api/v1/hello
        return "hello...Get";
    }