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Vert.x Web API Contract extends Vert.x Web to support OpenAPI 3, bringing to you a simple interface to build your router and mount security and validation handler.

If you are interested in building an application that routes API Requests to event bus, check out Vert.x Web API Service

Using Vert.x API Contract

To use Vert.x API Contract, add the following dependency to the dependencies section of your build descriptor:

  • Maven (in your pom.xml):

  • Gradle (in your build.gradle file):

dependencies {
 compile 'io.vertx:vertx-web-api-contract:4.0.0-milestone4'

HTTP Requests validation

Vert.x provides a validation framework that will validate requests for you and will put results of validation inside a container. To define a HTTPRequestValidationHandler:

var HTTPRequestValidationHandler = require("vertx-web-api-contract-js/http_request_validation_handler");
// Create Validation Handler with some stuff
var validationHandler = HTTPRequestValidationHandler.create().addQueryParam("parameterName", 'INT', true).addFormParamWithPattern("formParameterName", "a{4}", true).addPathParam("pathParam", 'FLOAT');

Then you can mount your validation handler:

var BodyHandler = require("vertx-web-js/body_handler");
// BodyHandler is required to manage body parameters like forms or json body

router.get("/awesome/:pathParam").handler(validationHandler.handle).handler(function (routingContext) {
  // Get Request parameters container
  var params = routingContext.get("parsedParameters");

  // Get parameters
  var parameterName = params.queryParameter("parameterName").getInteger();
  var formParameterName = params.formParameter("formParameterName").getString();
  var pathParam = params.pathParameter("pathParam").getFloat();
}).failureHandler(function (routingContext) {
  var failure = routingContext.failure();
  if (failure.getClass().getSimpleName() == 'ValidationException') {
    // Something went wrong during validation!
    var validationErrorMessage = failure.getMessage();

If validation succeeds, It returns request parameters inside RequestParameters, otherwise It will throw a fail inside RoutingContext with 400 status code and ValidationException failure.

Types of request parameters

Every parameter has a type validator, a class that describes the expected type of parameter. A type validator validates the value, casts it in required language type and then loads it inside a RequestParameter object. There are three ways to describe the type of your parameter:

Handling parameters

Now you can handle parameter values:

var params = routingContext.get("parsedParameters");
var awesomeParameter = params.queryParameter("awesomeParameter");
if ((awesomeParameter !== null && awesomeParameter !== undefined)) {
  if (!awesomeParameter.isEmpty()) {
    // Parameter exists and isn't empty
    // ParameterTypeValidator mapped the parameter in equivalent language object
    var awesome = awesomeParameter.getInteger();
  } else {
    // Parameter exists, but it's empty
} else {
  // Parameter doesn't exist (it's not required)

As you can see, every parameter is mapped in respective language objects. You can also get a json body:

var body = params.body();
if ((body !== null && body !== undefined)) {
  var jsonBody = body.getJsonObject();

Manage validation failures

A validation error fails the RoutingContext with 400 status code and ValidationException failure. You can manage these failures both at route level using failureHandler or at router level using errorHandler:

router.get("/awesome/:pathParam").handler(validationHandler.handle).handler(function (routingContext) {
  // Your logic
}).failureHandler(function (routingContext) {
  var failure = routingContext.failure();
  if (failure.getClass().getSimpleName() == 'ValidationException') {
    // Something went wrong during validation!
    var validationErrorMessage = failure.getMessage();

// Manage the validation failure for all routes in the router
router.errorHandler(400, function (routingContext) {
  if (routingContext.failure().getClass().getSimpleName() == 'ValidationException') {
    // Something went wrong during validation!
    var validationErrorMessage = routingContext.failure().getMessage();
  } else {
    // Unknown 400 failure happened

OpenAPI 3

Vert.x allows you to use your OpenAPI 3 specification directly inside your code using the design first approach. Vert.x-Web API Contract provides:

  • OpenAPI 3 compliant API specification validation with automatic loading of external Json schemas

  • Automatic request validation

  • Automatic mount of security validation handlers

You can also use the community project vertx-starter to generate server code from your OpenAPI 3 specification.

The Router Factory

You can create your web service based on OpenAPI 3 specification with OpenAPI3RouterFactory. This class, as name says, is a router factory based on your OpenAPI 3 specification. OpenAPI3RouterFactory is intended to give you a really simple user interface to use OpenAPI 3 related features. It includes:

  • Async loading of specification and its schema dependencies

  • Mount path with operationId or with combination of path and HTTP method

  • Automatic generation of validation handlers

  • Automatic conversion between OpenAPI style paths and Vert.x style paths

  • Lazy methods: operations are mounted in declaration order inside specification

  • Automatic mount of security handlers

Create a new router factory

To create a new router factory, use method OpenAPI3RouterFactory.create. As location It accepts absolute paths, local paths and local or remote URLs (HTTP or file protocol).

For example to load a spec from the local filesystem:

var OpenAPI3RouterFactory = require("vertx-web-api-contract-js/open_api3_router_factory");
OpenAPI3RouterFactory.create(vertx, "src/main/resources/petstore.yaml", function (ar, ar_err) {
  if (ar_err == null) {
    // Spec loaded with success
    var routerFactory = ar;
  } else {
    // Something went wrong during router factory initialization
    var exception = ar_err;

You can also construct a router factory from a remote spec:

var OpenAPI3RouterFactory = require("vertx-web-api-contract-js/open_api3_router_factory");
OpenAPI3RouterFactory.create(vertx, "", function (ar, ar_err) {
  if (ar_err == null) {
    // Spec loaded with success
    var routerFactory = ar;
  } else {
    // Something went wrong during router factory initialization
    var exception = ar_err;

Or, you can also access a private remote spec by passing one or more AuthorizationValue:

Code not translatable

You can also modify the behaviours of the router factory with RouterFactoryOptions.

Mount the handlers

Now load your first operation handlers. To load an handler use addHandlerByOperationId. To load a failure handler use addFailureHandlerByOperationId

You can, of course, add multiple handlers to same operation, without overwrite the existing ones.

For example:

routerFactory.addHandlerByOperationId("awesomeOperation", function (routingContext) {
  var params = routingContext.get("parsedParameters");
  var body = params.body();
  var jsonBody = body.getJsonObject();
  // Do something with body
routerFactory.addFailureHandlerByOperationId("awesomeOperation", function (routingContext) {
  // Handle failure

Now you can use parameter values as described above

Define security handlers

A security handler is defined by a combination of schema name and scope. You can mount only one security handler for a combination. For example:

routerFactory.addSecurityHandler("security_scheme_name", securityHandler);

You can of course use included Vert.x security handlers, for example:

var JWTAuthHandler = require("vertx-web-js/jwt_auth_handler");
routerFactory.addSecurityHandler("jwt_auth", JWTAuthHandler.create(jwtAuthProvider).handle);

When you generate the Router the Router Factory fails if For debugging/testing purpose

Not Implemented Error

Router Factory automatically mounts a default handler for operations without a specified handler. This default handler fails the routing context with 405 Method Not Allowed/501 Not Implemented error. You can enable/disable it with mountNotImplementedHandler and you can customize this error handling with errorHandler

Response Content Type Handler

Router Factory automatically mounts a ResponseContentTypeHandler handler when contract requires it. You can disable this feature with mountResponseContentTypeHandler

Operation model

If you need to access to your operation contract while handling the request, you can configure the router factory to push it inside the RoutingContext with operationModelKey. For example:

// Configure the operation model key and set options in router factory
options.operationModelKey = "operationPOJO";

// Add an handler that uses the operation model
routerFactory.addHandlerByOperationId("listPets", function (routingContext) {
  var operation = routingContext.get("operationPOJO");


Body Handler

Router Factory automatically mounts a BodyHandler to manage request bodies. You can configure the instance of BodyHandler (e.g. to change upload directory) with setBodyHandler.

multipart/form-data validation

The validation handler separates file uploads and form attributes as explained:

  • If the parameter doesn’t have an encoding associated field:

    • If the parameter has type: string and format: base64 or format: binary is a file upload with content-type application/octet-stream

    • Otherwise is a form attribute

  • If the parameter has the encoding associated field is a file upload

The form attributes are parsed and validated as other request parameters, while for file uploads the validation handler just checks the existence and the content type.

Custom global handlers

If you need to mount handlers that must be executed for each operation in your router before the operation specific handlers, you can use addGlobalHandler

Router factory handlers mount order

Handlers are loaded by the router factory in this order:

  1. Body handler

  2. Custom global handlers

  3. Global security handlers defined in upper spec level

  4. Operation specific security handlers

  5. Generated validation handler

  6. User handlers or "Not implemented" handler (if enabled)

Generate the router

When you are ready, generate the router and use it:

var router = routerFactory.getRouter();

var server = vertx.createHttpServer({
  "port" : 8080,
  "host" : "localhost"

This method can fail with a RouterFactoryException if you didn’t provide the required security handlers.