Provide a setting to use a different REST url during SSR execution

server.ts

@@ -81,6 +81,9 @@ let anonymousCache: LRU<string, any>;
 // extend environment with app config for server
 extendEnvironmentWithAppConfig(environment, appConfig);
 
+// The REST server base URL
+const REST_BASE_URL = environment.rest.ssrBaseUrl || environment.rest.baseUrl;
+
 // The Express app is exported so that it can be used by serverless Functions.
 export function app() {
 
@@ -156,7 +159,7 @@ export function app() {
    * Proxy the sitemaps
    */
   router.use('/sitemap**', createProxyMiddleware({
-    target: `${environment.rest.baseUrl}/sitemaps`,
+    target: `${REST_BASE_URL}/sitemaps`,
     pathRewrite: path => path.replace(environment.ui.nameSpace, '/'),
     changeOrigin: true,
   }));
@@ -165,7 +168,7 @@ export function app() {
    * Proxy the linksets
    */
   router.use('/signposting**', createProxyMiddleware({
-    target: `${environment.rest.baseUrl}`,
+    target: `${REST_BASE_URL}`,
     pathRewrite: path => path.replace(environment.ui.nameSpace, '/'),
     changeOrigin: true,
   }));
@@ -623,7 +626,7 @@ function start() {
  * The callback function to serve health check requests
  */
 function healthCheck(req, res) {
-  const baseUrl = `${environment.rest.baseUrl}${environment.actuators.endpointPath}`;
+  const baseUrl = `${REST_BASE_URL}${environment.actuators.endpointPath}`;
   axios.get(baseUrl)
     .then((response) => {
       res.status(response.status).send(response.data);

src/app/app.config.ts

@@ -54,6 +54,7 @@ import {
 } from './app-routes';
 import { BROWSE_BY_DECORATOR_MAP } from './browse-by/browse-by-switcher/browse-by-decorator';
 import { AuthInterceptor } from './core/auth/auth.interceptor';
+import { DspaceRestInterceptor } from './core/dspace-rest/dspace-rest.interceptor';
 import { LocaleInterceptor } from './core/locale/locale.interceptor';
 import { LogInterceptor } from './core/log/log.interceptor';
 import {
@@ -148,6 +149,11 @@ export const commonAppConfig: ApplicationConfig = {
       useClass: LogInterceptor,
       multi: true,
     },
+    {
+      provide: HTTP_INTERCEPTORS,
+      useClass: DspaceRestInterceptor,
+      multi: true,
+    },
     // register the dynamic matcher used by form. MUST be provided by the app module
     ...DYNAMIC_MATCHER_PROVIDERS,
     provideCore(),

src/app/core/dspace-rest/dspace-rest.interceptor.spec.ts

@@ -0,0 +1,194 @@
+import {
+  HTTP_INTERCEPTORS,
+  HttpClient,
+} from '@angular/common/http';
+import {
+  HttpClientTestingModule,
+  HttpTestingController,
+} from '@angular/common/http/testing';
+import { PLATFORM_ID } from '@angular/core';
+import { TestBed } from '@angular/core/testing';
+
+import {
+  APP_CONFIG,
+  AppConfig,
+} from '../../../config/app-config.interface';
+import { DspaceRestInterceptor } from './dspace-rest.interceptor';
+import { DspaceRestService } from './dspace-rest.service';
+
+describe('DspaceRestInterceptor', () => {
+  let httpMock: HttpTestingController;
+  let httpClient: HttpClient;
+  const appConfig: Partial<AppConfig> = {
+    rest: {
+      ssl: false,
+      host: 'localhost',
+      port: 8080,
+      nameSpace: '/server',
+      baseUrl: 'http://api.example.com/server',
+    },
+  };
+  const appConfigWithSSR: Partial<AppConfig> = {
+    rest: {
+      ssl: false,
+      host: 'localhost',
+      port: 8080,
+      nameSpace: '/server',
+      baseUrl: 'http://api.example.com/server',
+      ssrBaseUrl: 'http://ssr.example.com/server',
+    },
+  };
+
+  describe('When SSR base URL is not set ', () => {
+    describe('and it\'s in the browser', () => {
+      beforeEach(() => {
+        TestBed.configureTestingModule({
+          imports: [HttpClientTestingModule],
+          providers: [
+            DspaceRestService,
+            {
+              provide: HTTP_INTERCEPTORS,
+              useClass: DspaceRestInterceptor,
+              multi: true,
+            },
+            { provide: APP_CONFIG, useValue: appConfig },
+            { provide: PLATFORM_ID, useValue: 'browser' },
+          ],
+        });
+
+        httpMock = TestBed.inject(HttpTestingController);
+        httpClient = TestBed.inject(HttpClient);
+      });
+
+      it('should not modify the request', () => {
+        const url = 'http://api.example.com/server/items';
+        httpClient.get(url).subscribe((response) => {
+          expect(response).toBeTruthy();
+        });
+
+        const req = httpMock.expectOne(url);
+        expect(req.request.url).toBe(url);
+        req.flush({});
+        httpMock.verify();
+      });
+    });
+
+    describe('and it\'s in SSR mode', () => {
+      beforeEach(() => {
+        TestBed.configureTestingModule({
+          imports: [HttpClientTestingModule],
+          providers: [
+            DspaceRestService,
+            {
+              provide: HTTP_INTERCEPTORS,
+              useClass: DspaceRestInterceptor,
+              multi: true,
+            },
+            { provide: APP_CONFIG, useValue: appConfig },
+            { provide: PLATFORM_ID, useValue: 'server' },
+          ],
+        });
+
+        httpMock = TestBed.inject(HttpTestingController);
+        httpClient = TestBed.inject(HttpClient);
+      });
+
+      it('should not replace the base URL', () => {
+        const url = 'http://api.example.com/server/items';
+
+        httpClient.get(url).subscribe((response) => {
+          expect(response).toBeTruthy();
+        });
+
+        const req = httpMock.expectOne(url);
+        expect(req.request.url).toBe(url);
+        req.flush({});
+        httpMock.verify();
+      });
+    });
+  });
+
+  describe('When SSR base URL is set ', () => {
+    describe('and it\'s in the browser', () => {
+      beforeEach(() => {
+        TestBed.configureTestingModule({
+          imports: [HttpClientTestingModule],
+          providers: [
+            DspaceRestService,
+            {
+              provide: HTTP_INTERCEPTORS,
+              useClass: DspaceRestInterceptor,
+              multi: true,
+            },
+            { provide: APP_CONFIG, useValue: appConfigWithSSR },
+            { provide: PLATFORM_ID, useValue: 'browser' },
+          ],
+        });
+
+        httpMock = TestBed.inject(HttpTestingController);
+        httpClient = TestBed.inject(HttpClient);
+      });
+
+      it('should not modify the request', () => {
+        const url = 'http://api.example.com/server/items';
+        httpClient.get(url).subscribe((response) => {
+          expect(response).toBeTruthy();
+        });
+
+        const req = httpMock.expectOne(url);
+        expect(req.request.url).toBe(url);
+        req.flush({});
+        httpMock.verify();
+      });
+    });
+
+    describe('and it\'s in SSR mode', () => {
+      beforeEach(() => {
+        TestBed.configureTestingModule({
+          imports: [HttpClientTestingModule],
+          providers: [
+            DspaceRestService,
+            {
+              provide: HTTP_INTERCEPTORS,
+              useClass: DspaceRestInterceptor,
+              multi: true,
+            },
+            { provide: APP_CONFIG, useValue: appConfigWithSSR },
+            { provide: PLATFORM_ID, useValue: 'server' },
+          ],
+        });
+
+        httpMock = TestBed.inject(HttpTestingController);
+        httpClient = TestBed.inject(HttpClient);
+      });
+
+      it('should replace the base URL', () => {
+        const url = 'http://api.example.com/server/items';
+        const ssrBaseUrl = appConfigWithSSR.rest.ssrBaseUrl;
+
+        httpClient.get(url).subscribe((response) => {
+          expect(response).toBeTruthy();
+        });
+
+        const req = httpMock.expectOne(ssrBaseUrl + '/items');
+        expect(req.request.url).toBe(ssrBaseUrl + '/items');
+        req.flush({});
+        httpMock.verify();
+      });
+
+      it('should not replace any query param containing the base URL', () => {
+        const url = 'http://api.example.com/server/items?url=http://api.example.com/server/item/1';
+        const ssrBaseUrl = appConfigWithSSR.rest.ssrBaseUrl;
+
+        httpClient.get(url).subscribe((response) => {
+          expect(response).toBeTruthy();
+        });
+
+        const req = httpMock.expectOne(ssrBaseUrl + '/items?url=http://api.example.com/server/item/1');
+        expect(req.request.url).toBe(ssrBaseUrl + '/items?url=http://api.example.com/server/item/1');
+        req.flush({});
+        httpMock.verify();
+      });
+    });
+  });
+});

src/app/core/dspace-rest/dspace-rest.interceptor.ts

@@ -0,0 +1,52 @@
+import { isPlatformBrowser } from '@angular/common';
+import {
+  HttpEvent,
+  HttpHandler,
+  HttpInterceptor,
+  HttpRequest,
+} from '@angular/common/http';
+import {
+  Inject,
+  Injectable,
+  PLATFORM_ID,
+} from '@angular/core';
+import { Observable } from 'rxjs';
+
+import {
+  APP_CONFIG,
+  AppConfig,
+} from '../../../config/app-config.interface';
+import { isEmpty } from '../../shared/empty.util';
+
+@Injectable()
+/**
+ * This Interceptor is used to use the configured base URL for the request made during SSR execution
+ */
+export class DspaceRestInterceptor implements HttpInterceptor {
+
+  /**
+   * Contains the configured application base URL
+   * @protected
+   */
+  protected baseUrl: string;
+  protected ssrBaseUrl: string;
+
+  constructor(
+    @Inject(APP_CONFIG) protected appConfig: AppConfig,
+    @Inject(PLATFORM_ID) private platformId: string,
+  ) {
+    this.baseUrl = this.appConfig.rest.baseUrl;
+    this.ssrBaseUrl = this.appConfig.rest.ssrBaseUrl;
+  }
+
+  intercept(request: HttpRequest<unknown>, next: HttpHandler): Observable<HttpEvent<unknown>> {
+    if (isPlatformBrowser(this.platformId) || isEmpty(this.ssrBaseUrl) || this.baseUrl === this.ssrBaseUrl) {
+      return next.handle(request);
+    }
+
+    // Different SSR Base URL specified so replace it in the current request url
+    const url = request.url.replace(this.baseUrl, this.ssrBaseUrl);
+    const newRequest: HttpRequest<any> = request.clone({ url });
+    return next.handle(newRequest);
+  }
+}

src/app/core/services/server-hard-redirect.service.spec.ts

@@ -1,13 +1,14 @@
 import { TestBed } from '@angular/core/testing';
 
+import { environment } from '../../../environments/environment.test';
 import { ServerHardRedirectService } from './server-hard-redirect.service';
 
 describe('ServerHardRedirectService', () => {
 
   const mockRequest = jasmine.createSpyObj(['get']);
   const mockResponse = jasmine.createSpyObj(['redirect', 'end']);
 
-  const service: ServerHardRedirectService = new ServerHardRedirectService(mockRequest, mockResponse);
+  const service: ServerHardRedirectService = new ServerHardRedirectService(environment, mockRequest, mockResponse);
   const origin = 'https://test-host.com:4000';
 
   beforeEach(() => {

src/app/core/services/server-hard-redirect.service.ts

@@ -7,10 +7,15 @@
   Response,
 } from 'express';
 
+import {
+  APP_CONFIG,
+  AppConfig,
+} from '../../../config/app-config.interface';
 import {
   REQUEST,
   RESPONSE,
 } from '../../../express.tokens';
+import { isNotEmpty } from '../../shared/empty.util';
 import { HardRedirectService } from './hard-redirect.service';
 
 /**
@@ -20,6 +25,7 @@
 export class ServerHardRedirectService extends HardRedirectService {
 
   constructor(
+    @Inject(APP_CONFIG) protected appConfig: AppConfig,
     @Inject(REQUEST) protected req: Request,
     @Inject(RESPONSE) protected res: Response,
   ) {
@@ -35,17 +41,22 @@
    *    optional HTTP status code to use for redirect (default = 302, which is a temporary redirect)
    */
   redirect(url: string, statusCode?: number) {
-
     if (url === this.req.url) {
       return;
     }
 
+    let redirectUrl = url;
+    // If redirect url contains SSR base url then replace with public base url
+    if (isNotEmpty(this.appConfig.rest.ssrBaseUrl) && this.appConfig.rest.baseUrl !== this.appConfig.rest.ssrBaseUrl) {
+      redirectUrl = url.replace(this.appConfig.rest.ssrBaseUrl, this.appConfig.rest.baseUrl);
+    }
+
     if (this.res.finished) {
       const req: any = this.req;
       req._r_count = (req._r_count || 0) + 1;
 
       console.warn('Attempted to redirect on a finished response. From',
-        this.req.url, 'to', url);
+        this.req.url, 'to', redirectUrl);
 
       if (req._r_count > 10) {
         console.error('Detected a redirection loop. killing the nodejs process');
@@ -59,9 +70,9 @@
         status = 302;
       }
 
-      console.log(`Redirecting from ${this.req.url} to ${url} with ${status}`);
+      console.info(`Redirecting from ${this.req.url} to ${redirectUrl} with ${status}`);
 
-      this.res.redirect(status, url);
+      this.res.redirect(status, redirectUrl);
       this.res.end();
       // I haven't found a way to correctly stop Angular rendering.
       // So we just let it end its work, though we have already closed