HttpInterceptor
拦截 HttpRequest 并处理它们。
Intercepts and handles an HttpRequest or HttpResponse.
interface HttpInterceptor {
intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>>
}
参见
说明
大多数拦截器都会在外发的请求由 next.handle(transformedReq) 发给拦截器链中的下一个拦截器之前，对该请求进行转换。 拦截器还可以通过为 next.handle() 返回的流添加额外的 RxJS 操作符，来对响应事件流进行转换。
Most interceptors transform the outgoing request before passing it to the next interceptor in the chain, by calling next.handle(transformedReq). An interceptor may transform the response event stream as well, by applying additional RxJS operators on the stream returned by next.handle().
极少数情况下，拦截器也可以自己完全处理一个请求，并且组合出新的事件流来而不必调用 next.handle()。 这也是允许的，不过要时刻记住，这将会完全跳过所有后继拦截器。
More rarely, an interceptor may handle the request entirely, and compose a new event stream instead of invoking next.handle(). This is an acceptable behavior, but keep in mind that further interceptors will be skipped entirely.
另一种同样罕见但是有用的拦截器，会为单个请求在事件流上给出多个响应对象。
It is also rare but valid for an interceptor to return multiple responses on the event stream for a single request.
Further information available in the Usage Notes...
方法
标识并处理给定的 HTTP 请求。 Identifies and handles a given HTTP request. | ||||||
参数
返回值事件流的可观察值。
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使用说明
要想在整个应用中使用 HttpInterceptors 的同一个实例，就只能在 AppModule 模块中导入 HttpClientModule，并且把拦截器都添加到应用的根注入器中。 如果你在不同的模块中多次导入 HttpClientModule，则每次导入都会创建 HttpClientModule 的一个新复本，它将会覆盖根模块上提供的那些拦截器。
To use the same instance of HttpInterceptors for the entire app, import the HttpClientModule only in your AppModule, and add the interceptors to the root application injector . If you import HttpClientModule multiple times across different modules (for example, in lazy loading modules), each import creates a new copy of the HttpClientModule, which overwrites the interceptors provided in the root module.
