= Vert.x Web API Contract
:toc: left

Vert.x Web API Contract extends Vert.x Web to support https://www.openapis.org/[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 https://vertx.io/docs/vertx-web-api-service/java/[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`):

[source,xml,subs="+attributes"]
----
<dependency>
  <groupId>io.vertx</groupId>
  <artifactId>vertx-web-api-contract</artifactId>
  <version>${maven.version}</version>
</dependency>
----

* Gradle (in your `build.gradle` file):

[source,groovy,subs="+attributes"]
----
dependencies {
  compile 'io.vertx:vertx-web-api-contract:${maven.version}'
}
----

== 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 {@link io.vertx.ext.web.api.validation.HTTPRequestValidationHandler}:

[source,$lang]
----
{@link examples.ValidationExamples#example1}
----

Then you can mount your validation handler:

[source,$lang]
----
{@link examples.ValidationExamples#example2}
----

If validation succeeds, It returns request parameters inside {@link io.vertx.ext.web.api.RequestParameters},
otherwise It will throw a fail inside `RoutingContext` with 400 status code and {@link io.vertx.ext.web.api.validation.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 {@link io.vertx.ext.web.api.RequestParameter} object. There are three ways to describe the type of your parameter:

* There is a set of prebuilt types that you can use: {@link io.vertx.ext.web.api.validation.ParameterType}
* You can instantiate a custom instance of prebuilt type validators using static methods of {@link io.vertx.ext.web.api.validation.ParameterTypeValidator} and then load it into {@link io.vertx.ext.web.api.validation.HTTPRequestValidationHandler} using functions ending with `WithCustomTypeValidator`
* You can create your own `ParameterTypeValidator` implementing {@link io.vertx.ext.web.api.validation.ParameterTypeValidator} interface

=== Handling parameters
Now you can handle parameter values:

[source,$lang]
----
{@link examples.ValidationExamples#example3}
----

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

[source,$lang]
----
{@link examples.ValidationExamples#example4}
----

=== Manage validation failures
A validation error fails the `RoutingContext` with 400 status code and {@link io.vertx.ext.web.api.validation.ValidationException} failure.
You can manage these failures both at route level using {@link io.vertx.ext.web.Route#failureHandler} or at router level using {@link io.vertx.ext.web.Router#errorHandler}:

[source,$lang]
----
{@link examples.ValidationExamples#example5}
----

== 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 https://github.com/pmlopes/vertx-starter[`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 {@link io.vertx.ext.web.api.contract.openapi3.OpenAPI3RouterFactory}.
This class, as name says, is a router factory based on your OpenAPI 3 specification.
{@link io.vertx.ext.web.api.contract.openapi3.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 {@link io.vertx.ext.web.api.contract.openapi3.OpenAPI3RouterFactory#create(io.vertx.core.Vertx, java.lang.String, io.vertx.core.Handler)}.
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:

[source,$lang]
----
{@link examples.OpenAPI3Examples#constructRouterFactory}
----

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

[source,$lang]
----
{@link examples.OpenAPI3Examples#constructRouterFactoryFromUrl}
----

Or, you can also access a private remote spec by passing one or more https://github.com/swagger-api/swagger-parser#usage[AuthorizationValue]:

[source,$lang]
----
{@link examples.OpenAPI3Examples#constructRouterFactoryFromUrlWithAuthenticationHeader}
----

You can also modify the behaviours of the router factory with {@link io.vertx.ext.web.api.contract.RouterFactoryOptions}.

=== Mount the handlers
Now load your first operation handlers.
To load an handler use {@link io.vertx.ext.web.api.contract.openapi3.OpenAPI3RouterFactory#addHandlerByOperationId(java.lang.String, io.vertx.core.Handler)}.
To load a failure handler use {@link io.vertx.ext.web.api.contract.openapi3.OpenAPI3RouterFactory#addFailureHandlerByOperationId(java.lang.String, io.vertx.core.Handler)}

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

For example:

[source,$lang]
----
{@link examples.OpenAPI3Examples#addRoute}
----

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:

[source,$lang]
----
{@link examples.OpenAPI3Examples#addSecurityHandler}
----

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

[source,$lang]
----
{@link examples.OpenAPI3Examples#addJWT}
----

When you generate the {@link io.vertx.ext.web.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 501 `Not Implemented` error.
You can enable/disable it with {@link io.vertx.ext.web.api.contract.RouterFactoryOptions#setMountNotImplementedHandler}
and you can customize this error handling with {@link io.vertx.ext.web.Router#errorHandler}

=== Response Content Type Handler
Router Factory automatically mounts a {@link io.vertx.ext.web.handler.ResponseContentTypeHandler} handler when contract requires it.
You can disable this feature with {@link io.vertx.ext.web.api.contract.RouterFactoryOptions#setMountResponseContentTypeHandler}

=== 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 {@link io.vertx.ext.web.api.contract.RouterFactoryOptions#setOperationModelKey}. For example:

[source,$lang]
----
{@link examples.OpenAPI3Examples#addOperationModelKey}
----

=== Body Handler
Router Factory automatically mounts a {@link io.vertx.ext.web.handler.BodyHandler} to manage request bodies.
You can configure the instance of {@link io.vertx.ext.web.handler.BodyHandler} (e.g. to change upload directory) with {@link io.vertx.ext.web.api.contract.RouterFactory#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 operationin your router before the operation specific handlers, you can use {@link io.vertx.ext.web.api.contract.RouterFactory#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:

[source,$lang]
----
{@link examples.OpenAPI3Examples#generateRouter}
----

This method can fail with a {@link io.vertx.ext.web.api.contract.RouterFactoryException} if you didn't provide the required security handlers.

ifeval::["$lang" == "java"]
include::override/rxjava2.adoc[]
endif::[]
