@ngx-utils/cache

Service for transfer cached data from server
Example in @ngx-utils/universal-starter shows the way in which CacheService is used to cache all requests performed on server side and get cached data on client side.

Table of contents:

• Prerequisites
• Getting started

Installation browser.module.ts server.module.ts Application cache key

• API
• Example of usage
• License

Prerequisites

This package depends on @angular v5.
For @angular v4 use 2.0.1 version.

Getting started

Installation

Install @ngx-utils/cache from npm:

npm install @ngx-utils/cache --save

browser.module.ts

Add BrowserCacheModule to your browser module:

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { BrowserCacheModule } from '@ngx-utils/cache/browser';
...
import { AppModule } from './app/app.module';
import { AppComponent } from './app/app.component';
...
@NgModule({
  imports: [
    BrowserModule.withServerTransition({appId: 'your-app-id'}),
    BrowserCacheModule.forRoot(),
    AppModule
    ...
  ],
  bootstrap: [AppComponent]
})
export class BrowserAppModule { }

server.module.ts

Add ServerCacheModule to your server module:

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { ServerModule } from '@angular/platform-server';
import { ServerCacheModule } from '@ngx-utils/cache/server';
...
import { AppModule } from './app/app.module';
import { AppComponent } from './app/app.component';
...
@NgModule({
  imports: [
    BrowserModule.withServerTransition({ appId: 'your-app-id' }),
    ServerModule,
    ServerCacheModule.forRoot(),
    AppModule
    ...
  ],
  bootstrap: [AppComponent]
})
export class ServerAppModule { }

Application cache key

You can also specify application cache key:

BrowserCacheModule.forRoot({ appCacheKey: 'YOUR_CACHE_KEY' })
...
ServerCacheModule.forRoot({ appCacheKey: 'YOUR_CACHE_KEY' })

By default this key is __APP_CACHE__ and it used for create global variable (property in window object)

API

CacheService has following methods:

• has(key: string): boolean check if key exist in cache;
• set(key: string, value: any): void put some value to cache;
• get(key: string): any get value from cache by key;
• clear(key: string): void remove value from cache by key;
• clearAll(): void clear cache;
• dehydrate(): { [key: string]: any } convert data from cache to JSON;
• toJSON(): { [key: string]: any } convert data from cache to JSON;
• rehydrate(json: { [key: string]: any }): void set data from JSON to cache;

Example of usage

Following example shows how to cache all GET requests, performed on server side, and get cached data in browser (and don't send requests second time).
First of all we need create interceptor:

import { isPlatformBrowser, isPlatformServer } from '@angular/common';
import {
  HttpEvent,
  HttpHandler,
  HttpInterceptor,
  HttpRequest,
  HttpResponse
} from '@angular/common/http';
import { Inject, Injectable, PLATFORM_ID } from '@angular/core';
import { CacheService } from '@ngx-utils/cache';
import { Observable } from 'rxjs/Observable';
import { of } from 'rxjs/observable/of';
import { tap } from 'rxjs/operators/tap';

@Injectable()
export class CacheInterceptor implements HttpInterceptor {
  constructor(
    private cache: CacheService,
    @Inject(PLATFORM_ID) private platformId: Object
  ) {}

  intercept(
    request: HttpRequest<any>,
    next: HttpHandler
  ): Observable<HttpEvent<any>> {
    if (request.method !== 'GET') {
      return next.handle(request);
    }

    if (
      isPlatformBrowser(this.platformId) &&
      this.cache.has(request.urlWithParams)
    ) {
      const response = new HttpResponse({
        body: this.cache.get(request.urlWithParams),
        status: 200
      });
      return of(response).pipe(
        tap(() => this.cache.clear(request.urlWithParams))
      );
    }

    return next.handle(request).pipe(
      tap((response: any) => {
        if (isPlatformServer(this.platformId)) {
          this.cache.set(request.urlWithParams, response.body);
        }
      })
    );
  }
}

Than import it to app's main module:

import { HTTP_INTERCEPTORS, HttpClientModule } from '@angular/common/http';
import { NgModule } from '@angular/core';
import { BrowserModule  } from '@angular/platform-browser';

import { AppComponent } from './app.component';
import { AppRoutingModule } from './app-routing.module';
import { CacheInterceptor } from './cache.interceptor';

@NgModule({
 imports: [
  BrowserModule,
  HttpModule,
  AppRoutingModule
  ...
 ],
 declarations: [AppComponent],
 providers: [
   {
      provide: HTTP_INTERCEPTORS,
      multi: true,
      useClass: CacheInterceptor
    }
 ]
})
export class AppModule { }

License

The MIT License (MIT)