Response Filter

Ts.ED response filter provide a ResponseFilter decorator to decorate a class and handle data returned by the endpoint before sending it to your consumer. The decorator take a Content-Type value to define when the class must be used to transform data to the expected result.

It's the right place to implement your own serialization logic. For example, you can define a Response filter to transform data to an XML content or wrap the data into another generic object.

With this decorator, you are able to define multiple Response Filter (but only by Content-Type). Ts.ED will choose the better Response Filter according to the Accept HTTP header on the request object, when present, or fallback to the default Response filter.

Xml Filter

By using the appropriate Content-Type, you can define a Xml serializer as following:

XmlResponseFilter.ts

import {ResponseFilter, ResponseFilterMethods} from "@tsed/platform-response-filter";
import {Context} from "@tsed/platform-params";

@ResponseFilter("text/xml")
export class XmlResponseFilter implements ResponseFilterMethods {
  transform(data: any, ctx: Context) {
    return jsToXML(data);
  }
}

UserCtrl.ts

import {Configuration} from "@tsed/di";
import {Returns} from "@tsed/schema";

@Controller("/users")
export class UsersCtrl {
  @Get("/:id")
  @(Returns(200, User).ContentType("application/json"))
  @(Returns(200, String).ContentType("text/xml"))
  async getUser(@PathParams("id") id: string) {
    return new User({id});
  }
}

Server.ts

import {Configuration} from "@tsed/di";
import {XmlResponseFilter} from "./filters/XmlResponseFilter.js";

@Configuration({
  responseFilters: [
    XmlResponseFilter
  ]
})

UsersCtrl.spec.ts

import {PlatformTest} from "@tsed/platform-http/testing";
import * as SuperTest from "supertest";
import {UsersCtrl} from "./UsersCtrl.js";
import {Server} from "../../Server.js";

describe("UserCtrl", () => {
  let request: SuperTest.Agent;

  before(
    PlatformTest.bootstrap(Server, {
      mount: {
        "/rest": [UsersCtrl]
      },
      responseFilters: [XmlResponseFilter]
    })
  );
  before(() => {
    request = SuperTest(PlatformTest.callback());
  });
  after(PlatformTest.reset);
  it("should return the xml format", async () => {
    const response = await request
      .get("/rest/users/1")
      .set({
        Accept: "text/xml"
      })
      .expect(200);

    expect(response.text).toEqual("<xml>...</xml>");
  });
  it("should return the default format", async () => {
    const response = await request.get("/rest/users/1").expect(200);

    expect(response.body).toEqual({id: "1"});
  });
});

WARNING

Don't forget to register your Response Filter by adding your class to responseFilters field on the server configuration.

Wrap responses

One of the usage of the Response Filter could be to wrap all returned data into a generic object. To doing that, use the application/json Content-Type with the ResponseFilter decorator to wrap data to the expected result:

WrapperResponseFilter.ts

import {ResponseFilter, ResponseFilterMethods} from "@tsed/platform-response-filter";
import {Context} from "@tsed/platform-params";

@ResponseFilter("application/json")
export class WrapperResponseFilter implements ResponseFilterMethods {
  transform(data: any, ctx: Context) {
    return {data, errors: [], links: []};
  }
}

UserCtrl.ts

import {Configuration} from "@tsed/di";
import {Returns} from "@tsed/schema";

@Controller("/users")
export class UsersCtrl {
  @Get("/:id")
  @(Returns(200, User).ContentType("application/json"))
  @(Returns(200, String).ContentType("text/xml"))
  async getUser(@PathParams("id") id: string) {
    return new User({id});
  }
}

Server.ts

import {Configuration} from "@tsed/di";
import {WrapperResponseFilter} from "./filters/WrapperResponseFilter";

@Configuration({
  responseFilters: [
    WrapperResponseFilter
  ]
})

UsersCtrl.spec.ts

import {PlatformTest} from "@tsed/platform-http/testing";
import * as SuperTest from "supertest";
import {UsersCtrl} from "./UsersCtrl.js";
import {Server} from "../../Server.js";

describe("UserCtrl", () => {
  let request: SuperTest.Agent;

  before(
    PlatformTest.bootstrap(Server, {
      mount: {
        "/rest": [UsersCtrl]
      },
      responseFilters: [XmlResponseFilter]
    })
  );
  before(() => {
    request = SuperTest(PlatformTest.callback());
  });
  after(PlatformTest.reset);
  it("should return the wrapped data", async () => {
    const response = await request.get("/rest/users/1").expect(200);

    expect(response.body).toEqual({data: {id: "1"}, errors: [], links: []});
  });
});

WARNING

The wrapper won't be documented in your generated swagger.json!

Handle all responses

By using the */* Content-Type value given to the ResponseFilter you can intercept all data.

import {ResponseFilter, ResponseFilterMethods} from "@tsed/platform-response-filter";
import {Context} from "@tsed/platform-params";

@ResponseFilter("*/*")
export class AnyResponseFilter implements ResponseFilterMethods {
  transform(data: any, ctx: Context) {
    // do something
    return data;
  }
}

Pagination

The following advanced example will show you how you can combine the different Ts.ED features to describe Pagination. The used features are the following:

• Generics
• Function programming to declare models
• For decorator to declare a custom model for JsonSchema, OS2 or OS3.
• Response Filter to manage paginated response.

ProductsCtrl.ts

import {QueryParams} from "@tsed/platform-params";
import {Get, Returns} from "@tsed/schema";
import {Controller} from "@tsed/di";
import {Pageable} from "../models/Pageable";
import {Pagination} from "../models/Pagination";
import {Product} from "../models/Product";

@Controller("/pageable")
class ProductsCtrl {
  @Get("/")
  @Returns(206, Pagination).Of(Product).Title("PaginatedProduct")
  @Returns(200, Pagination).Of(Product).Title("PaginatedProduct")
  get(@QueryParams() pageableOptions: Pageable, @QueryParams("all") all: boolean) {
    return new Pagination<Product>({
      data: [
        new Product({
          id: "100",
          title: "CANON D3000"
        })
      ],
      totalCount: all ? 1 : 100, // just for test,
      pageable: pageableOptions
    });
  }
}

Pageable.ts

import {isString} from "@tsed/core";
import {OnDeserialize} from "@tsed/json-mapper";
import {array, Default, Description, For, Integer, Min, oneOf, SpecTypes, string} from "@tsed/schema";

class Pageable {
  @Integer()
  @Min(0)
  @Default(0)
  @Description("Page number.")
  page: number = 0;

  @Integer()
  @Min(1)
  @Default(20)
  @Description("Number of objects per page.")
  size: number = 20;

  @For(SpecTypes.JSON, oneOf(string(), array().items(string()).maxItems(2)))
  @For(SpecTypes.OPENAPI, array().items(string()).maxItems(2))
  @OnDeserialize((value: string | string[]) => (isString(value) ? value.split(",") : value))
  @Description(
    "Sorting criteria: property(,asc|desc). Default sort order is ascending. Multiple sort criteria are supported."
  )
  sort: string | string[];

  constructor(options: Partial<Pageable>) {
    options.page && (this.page = options.page);
    options.size && (this.size = options.size);
    options.sort && (this.sort = options.sort);
  }

  get offset() {
    return this.page ? this.page * this.limit : 0;
  }

  get limit() {
    return this.size;
  }
}

Pagination.ts

import {CollectionOf, Default, Generics, Integer, MinLength} from "@tsed/schema";
import {Pageable} from "./Pageable";

export class PaginationLink {
  @Property()
  next: string;

  @Property()
  prev: string;
}

@Generics("T")
export class Pagination<T> extends Pageable {
  @CollectionOf("T")
  data: T[];

  @Integer()
  @MinLength(0)
  @Default(0)
  totalCount: number = 0;

  @Property()
  links: PaginationLink = new PaginationLink();

  constructor({data, totalCount, pageable}: Partial<Pagination<T>> & {pageable: Pageable}) {
    super(pageable);
    data && (this.data = data);
    totalCount && (this.totalCount = totalCount);
  }
}

Product.ts

import {Property} from "@tsed/schema";

class Product {
  @Property()
  id: string;

  @Property()
  title: string;

  constructor({id, title}: Partial<Product> = {}) {
    id && (this.id = id);
    title && (this.title = title);
  }
}

PaginationFilter.ts

import {PlatformContext} from "@tsed/platform-http";
import {ResponseFilter, ResponseFilterMethods} from "@tsed/platform-response-filter";
import {Pagination} from "../models/Pagination";

@ResponseFilter("application/json")
class PaginationFilter implements ResponseFilterMethods {
  transform(data: unknown, ctx: PlatformContext): any {
    if (ctx.data instanceof Pagination) {
      // /!\ don't modify the ctx.data. at this step, the serializer has already been called.

      if (ctx.data.totalCount > (ctx.data.pageable.page + 1) * ctx.data.pageable.size) {
        ctx.response.status(206);
        data.links.next = `${ctx.request.url}?page=${ctx.data.pageable.page + 1}&size=${ctx.data.pageable.size}`;
      }

      if (ctx.data.pageable.page > 0) {
        data.links.prev = `${ctx.request.url}?page=${ctx.data.pageable.page - 1}&size=${ctx.data.pageable.size}`;
      }
    }

    return data;
  }
}

ProductsCtrl.spec.ts

import {Property} from "@tsed/schema";

class Product {
  @Property()
  id: string;

  @Property()
  title: string;

  constructor({id, title}: Partial<Product> = {}) {
    id && (this.id = id);
    title && (this.title = title);
  }
}