Angular in-memory-web-api

An in-memory web api for Angular demos and tests.

It intercepts Angular Http requests that would otherwise go to the remote server via the Angular XHRBackend service

LIMITATIONS

The in-memory-web-api exists primarily to support the Angular documentation. It is not supposed to emulate every possible real world web API and is not intended for production use.

Most importantly, it is always experimental. We will make breaking changes and we won't feel bad about it because this is a development tool, not a production product. We do try to tell you about such changes in the CHANGELOG.md and we fix bugs as fast as we can.

UPDATE NOTICE

As of v.0.1.0, the npm package was renamed from angular2-in-memory-web-api to its current name, angular-in-memory-web-api. All versions after 0.0.21 are shipped under this name. Be sure to update your package.json and import statements.

HTTP request handling

This in-memory web api service processes an HTTP request and returns an Observable of HTTP Response object in the manner of a RESTy web api. It natively handles URI patterns in the form :base/:collectionName/:id?

Examples:

  // for requests to an `api` base URL that gets heroes from a 'heroes' collection 
  GET api/heroes          // all heroes
  GET api/heroes/42       // the character with id=42
  GET api/heroes?name=^j  // 'j' is a regex; returns heroes whose name starting with 'j' or 'J'
  GET api/heroes.json/42  // ignores the ".json"

Commands

The service also accepts "commands" that can, for example, reconfigure the service and reset the database.

When the last segment of the api base path is "commands", the collectionName is treated as the command. Example URLs:

  commands/resetdb   // Reset the "database" to its original state
  commands/config    // Get or update this service's config object

Commands are "hot", meaning they are always executed immediately whether or not someone subscribes to the returned observable.

Usage:

  http.post('commands/resetdb', undefined);
  http.get('commands/config');
  http.post('commands/config', '{"delay":1000}');

Basic usage

Create an InMemoryDataService class that implements InMemoryDbService.

At minimum it must implement createDb which creates a "database" hash whose keys are collection names and whose values are arrays of collection objects to return or update. For example:

import { InMemoryDbService } from 'angular-in-memory-web-api';

export class InMemHeroService implements InMemoryDbService {
  createDb() {
    let heroes = [
      { id: '1', name: 'Windstorm' },
      { id: '2', name: 'Bombasto' },
      { id: '3', name: 'Magneta' },
      { id: '4', name: 'Tornado' }
    ];
    return {heroes};
  }
}

Register this module and your service implementation in AppModule.imports calling the forRoot static method with this service class and optional configuration object:

// other imports
import { HttpModule }           from '@angular/http';
import { InMemoryWebApiModule } from 'angular-in-memory-web-api';

import { InMemHeroService }     from '../app/hero-data';
@NgModule({
 imports: [
   HttpModule,
   InMemoryWebApiModule.forRoot(InMemHeroService),
   ...
 ],
 ...
})
export class AppModule { ... }

See examples in the Angular.io such as the Server Communication and Tour of Heroes chapters.

Always import the InMemoryWebApiModule after the HttpModule to ensure that the XHRBackend provider of the InMemoryWebApiModule supersedes all others.

Bonus Features

Some features are not readily apparent in the basic usage example.

The InMemoryBackendConfigArgs defines a set of options. Add them as the second forRoot argument:

  InMemoryWebApiModule.forRoot(InMemHeroService, { delay: 500 }),

Read the InMemoryBackendConfigArgs interface to learn about these options.

Request evaluation order

This service can evaluate requests in multiple ways depending upon the configuration. Here's how it reasons:

If it looks like a command, process as a command
If the HTTP method is overridden
If the resource name (after the api base path) matches one of the configured collections, process that
If not but the Config.passThruUnknownUrl flag is true, try to pass the request along to a real XHRBackend.
Return a 404.

See the handleRequest method implementation for details.

Default delayed response

By default this service adds a 500ms delay (see InMemoryBackendConfig.delay) to all requests to simulate round-trip latency. You can eliminate that or extend it by setting a different value:

  InMemoryWebApiModule.forRoot(InMemHeroService, { delay: 0 }),    // no delay
  InMemoryWebApiModule.forRoot(InMemHeroService, { delay: 1500 }), // 1.5 second delay

Simple query strings

Pass custom filters as a regex pattern via query string. The query string defines which property and value to match.

Format: /app/heroes/?propertyName=regexPattern

The following example matches all names start with the letter 'j' or 'J' in the heroes collection.

/app/heroes/?name=^j

Search pattern matches are case insensitive by default. Set config.caseSensitiveSearch = true if needed.

Pass thru to a live XHRBackend

If an existing, running remote server should handle requests for collections that are not in the in-memory database, set Config.passThruUnknownUrl: true. This service will forward unrecognized requests via a base version of the Angular XHRBackend.

parseUrl and your override

The parseUrl parses the request URL into a ParsedUrl object. ParsedUrl is a public interface whose properties guide the in-memory web api as it processes the request.

Default parseUrl

Default parsing depends upon certain values of config: apiBase, host, and urlRoot. Read the source code for the complete story.

Configuring the apiBase yields the most interesting changes to parseUrl behavior:

For apiBase=undefined and url='http://localhost/api/customers/42'
```
{base: 'api/', collectionName: 'customers', id: '42', ...}
```
For apiBase='some/api/root/' and url='http://localhost/some/api/root/customers'
```
{base: 'some/api/root/', collectionName: 'customers', id: undefined, ...}
```

For apiBase='/' and url='http://localhost/customers'

{base: '/', collectionName: 'customers', id: undefined, ...}

The actual api base segment values are ignored. Only the number of segments matters. The following api base strings are considered identical: 'a/b' ~ 'some/api/' ~ `two/segments'

This means that URLs that work with the in-memory web api may be rejected by the real server.

Custom parseUrl

You can override the default by implementing a parseUrl method in your InMemoryDbService. Such a method must take the incoming request URL string and return a ParsedUrl object.

Assign your alternative to InMemDbService['parseUrl']

responseInterceptor

You can morph the response returned by the default HTTP methods, called by collectionHandler, to suit your needs by adding a responseInterceptor method to your InMemoryDbService class. The collectionHandler calls your interceptor like this:

responseOptions = this.responseInterceptor(responseOptions, requestInfo);

HTTP method interceptors

If you make requests this service can't handle but still want an in-memory database to hold values, override the way this service handles any HTTP method by implementing a method in your InMemoryDbService that does the job.

The InMemoryDbService method name must be the same as the HTTP method name but all lowercase. This service calls it with an HttpMethodInterceptorArgs object. For example, your HTTP GET interceptor would be called like this: e.g., yourInMemDbService["get"](interceptorArgs).

Your method can have two possible returns:

null - the service will continue on with its default processing (checking the collection or falling back to a different backend). This is useful if you only wish to handle processing for certain paths in the given HTTP method.
Observable<Response> - your code has handled the request and the response is available from this observable. It should be "cold".

Your method must return one of these two values.

The HttpMethodInterceptorArgs (as of this writing) are:

requestInfo: RequestInfo;           // parsed request
db: Object;                         // the current in-mem database collections
config: InMemoryBackendConfigArgs;  // the current config
passThruBackend: ConnectionBackend; // pass through backend, if it exists

Examples

The file examples/hero-data.service.ts is an example of a Hero-oriented InMemoryDbService, derived from the HTTP Client sample in the Angular documentation.

To try it, add the following line to AppModule.imports

InMemoryWebApiModule.forRoot(HeroDataService)

That file also has a HeroDataOverrideService derived class that demonstrates overriding the parseUrl method and it has a "cold" HTTP GET interceptor.

Add the following line to AppModule.imports to see this version of the data service in action:

InMemoryWebApiModule.forRoot(HeroDataOverrideService)

To Do

add tests (shameful omission!)

Build Instructions

Mostly gulp driven.

The following describes steps for updating from one Angular version to the next

This is essential even when there are no changes of real consequence. Neglecting to synchronize Angular 2 versions triggers typescript definition duplication error messages when compiling your application project.

gulp bump - up the package version number
update CHANGELOG.MD to record the change
update the dependent version(s) in package.json
npm install the new package(s) (make sure they really do install!)
npm list --depth=0
consider updating typings, install individually/several:

  npm install @types/jasmine @types/node --save-dev

gulp clean - clear out all generated text
npm run tsc to confirm the project compiles w/o error (sanity check)

-- NO TESTS YET ... BAD --

gulp build
commit and push
npm publish
Fix and validate angular.io docs samples
Add two tags to the release commit with for unpkg
- the version number
- 'latest'

Drynwynn/in-memory-web-api