Strong API mapping

Strongly typed API models. Mapping & validation. Use meaningful decorators. Don't repeat yourself.

Installation

$3

npm install reflect-metadata @vladbasin/strong-api-mapping

$3

yarn add reflect-metadata @vladbasin/strong-api-mapping

Usage

This is a generic mapping library. You can integrate it with any HTTP stack. Currently the following packages use this library:

- @vladbasin/strong-api-middleware - generic middleware library which can integrate with any HTTP stack, by introducing additional layers of request/response pipeline and with help of this library can support any HTTP stack.
- @vladbasin/strong-api-middleware-aws-lambda - complete e2e HTTP pipeline integration for AWS Lambda
- [@vladbasin/strong-api-middleware-express]() - IN PROGRESS - complete e2e HTTP pipeline integration for express server
- @vladbasin/strong-api-client - HTTP client which can use shared models to execute request. Therefore, no need to duplicate mapping & validation logic for API consumers & producers.

$3

1. Import reflect-metadata ONCE in your index file:

``typescript
import 'reflect-metadata';
`

2. Define your model

`typescript
import { body, header, path, query } from '@vladbasin/strong-api-mapping';

export class RequestPayload {
@path()
public userId!: number;

@path({ key: 'userId' })
public id!: number;

@query()
public name!: string;

@query()
public isAdmin!: boolean;

@query({ key: 'lastname' })
public surname!: string;

@query({ parser: String })
public cars!: string[];

@query({ parser: Number })
public cash!: number[];

@body()
public details!: DetailsType;

@header({ key: 'Content-Type' })
public contentType!: string;

@header({ key: 'X-Info', parser: String })
public info!: string[];
}
`

3. Define validation rules with Joi

`typescript
export const RequestPayloadSchema = Joi.object({
surname: Joi.string().min(10),
cars: Joi.array().max(3),
// other rules for field content...
});
`

4. Prepare RawApiRequest for mapping.
For example, @vladbasin/strong-api-middleware-aws-lambda already does it for you for AWS Lambda. But you can create your own middleware for your stack and use this library to do mapping & validation for you.

`typescript
// represents Query, Header, Route and Body values for HTTP request
export type RawApiRequestType = {
queryParams?: MaybeNullable>>;
multiValueQueryParams?: MaybeNullable>>;
pathParams?: MaybeNullable>>;
headers?: MaybeNullable>>;
multiValueHeaders?: MaybeNullable>>;
body?: MaybeNullable;
};
`

5. Call the following methods to map HTTP request to your model and vice versa with DRY principle

`typescript
// maps RawApiRequest to Model (RequestPayload) and validates it (throws CodedError with information if model is not valid)
mapRawApiRequestToPayload({
rawApiRequest,
PayloadConstructor: RequestPayload,
schema: RequestPayloadSchema,
});

// maps Model (RequestPayload) to RawApiRequest
mapPayloadToRawApiRequest(requestPayload);
`

Also applicable to response models (mapRawApiResponseToPayload(), mapPayloadToRawApiResponse()).

In case validation fails, the library throws CodedError instance with information which properties are not valid:
`typescript
{
message: 'ValidationError: "surname" is required'
code: 'ValidationFailed',
errors: [ { code: 'surname', message: 'any.required' } ],
}
`


Thus, you can share request/response models with your API consumers, so they don't need to repeat the same mapping & validation logic. See: @vladbasin/strong-api-client

Custom decorator/mapping

You can also specify custom mappings for custom decorator:

1. Define custom decorator

`typescript
import { defineDecorator, ParserType } from '@vladbasin/strong-api-mapping';

export const context = (options: { key?: string; parser?: ParserType }): PropertyDecorator =>
defineDecorator({
source: 'context',
useKey: true,
isKeyCaseSensitive: false,
key: options.key,
parser: options.parser,
isCustom: true,
});
`

2. Specify data for custom context

`typescript
mapRawApiRequestToPayload({
rawApiRequest,
PayloadConstructor: RequestPayload,
schema: RequestPayloadSchema,
customApiRequestData: {
context: {
customKey: 'customValue',
//...
},
},
});
``