Http context stores arbitrary user defined values and ensures type safety without actually knowing the types. It is backed by a Map and guarantees that keys do not clash.

See more...

class HttpContext {
  set<T>(token: HttpContextToken<T>, value: T): HttpContext
  get<T>(token: HttpContextToken<T>): T
  delete(token: HttpContextToken<unknown>): HttpContext
  has(token: HttpContextToken<unknown>): boolean
  keys(): IterableIterator<HttpContextToken<unknown>>
}

Description

This context is mutable and is shared between cloned requests unless explicitly specified.

Further information is available in the Usage Notes...

Methods

set()
Store a value in the context. If a value is already present it will be overwritten.
set<T>(token: HttpContextToken<T>, value: T): HttpContext Parameters token HttpContextToken<T> The reference to an instance of HttpContextToken. value T The value to store. Returns HttpContext: A reference to itself for easy chaining.

get()
Retrieve the value associated with the given token.
get<T>(token: HttpContextToken<T>): T Parameters token HttpContextToken<T> The reference to an instance of HttpContextToken. Returns T: The stored value or default if one is defined.

delete()
Delete the value associated with the given token.
delete(token: HttpContextToken<unknown>): HttpContext Parameters token HttpContextToken<unknown> The reference to an instance of HttpContextToken. Returns HttpContext: A reference to itself for easy chaining.

has()
Checks for existence of a given token.
has(token: HttpContextToken<unknown>): boolean Parameters token HttpContextToken<unknown> The reference to an instance of HttpContextToken. Returns boolean: True if the token exists, false otherwise.

keys()
keys(): IterableIterator<HttpContextToken<unknown>> Parameters There are no parameters. Returns IterableIterator<HttpContextToken<unknown>>: a list of tokens currently stored in the context.

Usage notes

Usage Example

// inside cache.interceptors.ts
export const IS_CACHE_ENABLED = new HttpContextToken<boolean>(() => false);

export class CacheInterceptor implements HttpInterceptor {

  intercept(req: HttpRequest<any>, delegate: HttpHandler): Observable<HttpEvent<any>> {
    if (req.context.get(IS_CACHE_ENABLED) === true) {
      return ...;
    }
    return delegate.handle(req);
  }
}

// inside a service

this.httpClient.get('/api/weather', {
  context: new HttpContext().set(IS_CACHE_ENABLED, true)
}).subscribe(...);