Add ability to pass in existing express application (#37)

- Solves inversify/InversifyJS#509

README.md

@@ -162,6 +162,18 @@ let container = new Container();
 let server = new InversifyExpressServer(container, null, { rootPath: "/api/v1" });
 ```
 
+## Using a custom express application
+It is possible to pass a custom `express.Application` instance to `InversifyExpressServer`:
+
+```ts
+let container = new Container();
+
+let app = express();
+//Do stuff with app
+
+let server = new InversifyExpressServer(container, null, null, app);
+```
+
 ## Decorators
 
 ### `@Controller(path, [middleware, ...])`

src/server.ts

@@ -10,7 +10,7 @@ export class InversifyExpressServer  {
 
     private _router: express.Router;
     private _container: inversify.interfaces.Container;
-    private _app: express.Application = express();
+    private _app: express.Application;
     private _configFn: interfaces.ConfigFunction;
     private _errorConfigFn: interfaces.ConfigFunction;
     private _routingConfig: interfaces.RoutingConfig;
@@ -23,13 +23,15 @@ export class InversifyExpressServer  {
     constructor(
         container: inversify.interfaces.Container,
         customRouter?: express.Router,
-        routingConfig?: interfaces.RoutingConfig
+        routingConfig?: interfaces.RoutingConfig,
+        customApp?: express.Application
     ) {
         this._container = container;
         this._router = customRouter || express.Router();
         this._routingConfig = routingConfig || {
             rootPath: DEFAULT_ROUTING_ROOT_PATH
         };
+        this._app = customApp || express();
     }
 
     /**

test/server.test.ts

@@ -72,4 +72,15 @@ describe("Unit Test: InversifyExpressServer", () => {
 
     });
 
+    it("Should allow to provide a custom express application", () => {
+        let container = new Container();
+
+        let app = express();
+
+        let serverWithDefaultApp = new InversifyExpressServer(container);
+        let serverWithCustomApp = new InversifyExpressServer(container, null, null, app);
+
+        expect((serverWithCustomApp as any)._app).to.eq(app);
+        expect((serverWithDefaultApp as any)._app).to.not.eql((serverWithCustomApp as any)._app);
+    });
 });