My GSoC 2017 - Requests validation

• 08 August 2017
• web development,
• gsoc 2017,
• gsoc,
• vertx,
• vertx web,
• http validation

HTTP request validation it's a critical component of my project. HTTP requests validation needs to work well to get working all layers upon. I love to call that vertx-web validation framework (I love the word framework 😍)

Structure of Validation framework

The validation framework is located inside maven module vertx-web and package io.vertx.ext.web.validation. Following the Vert.x rules, there are Java interfaces for polyglot vertx-web interface and classes inside io.vertx.ext.web.validation.impl that implements the logic of the validation.

HTTPRequestValidationHandler and OpenAPI3RequestValidationHandler (request validator for OAS3) subclass BaseValidationHandler, the base class for validation. This class contains a map with parameter names as keys and ParameterValidationRule instances as values for every parameter location (query, path, header, cookie, form inside body). Every ParameterValidationRule contains a ParameterTypeValidation. To simplify things:

• BaseValidationHandler validates the request, in fact it iterates through parameters and calls ParameterValidationRule methods
• ParameterValidationRule abstracts a parameter and validates if parameter exists, if can be empty, ...
• ParameterTypeValidator abstracts the parameter type and validates the type

Every exceptions of validation framework are encapsulated inside ValidationException class.

Types of parameters

Most important part of validation is type validation. Type validation take a string or a list of strings as input and gives the parameter correctly parsed as output. I've built a rich set of type validators (mostly to support OpenAPI 3 parameter types):

• NumericTypeValidator to validate integers and floating point values
• StringTypeValidator to validate strings against a pattern
• BooleanTypeValidator to validate booleans
• JsonTypeValidator and XMLTypeValidator to validate json and xml against a schema
• EnumTypeValidator to validate enums
• ObjectTypeValidator and ArrayTypeValidator to validate objects and array
• AnyOfTypeValidator and OneOfTypeValidator to validate json schema like anyOf and oneOf

To instance this classes, there are static methods inside ParameterTypeValidator. Of course, user can subclass ParameterTypeValidator to create its custom type validator.

I've also created a set of prebuilt instances of this type validators inside ParameterType enum, with some common patterns like hostname, email, ...

Encapsulating parsed parameters

After type validation parameter is parsed and then encapsulated in an object called RequestParameter. Every object is mapped into equivalent language type, for example: if we declare a parameter as integer, we receive (in Java) Integer object.

When user wants to handle parameters, he can retrieve the RequestParameters from RoutingContext. RequestParameters encapsulate all RequestParameter objects filtered by location. For example:

router.get("/awesomePath")
  .handler(superAwesomeValidationHandler)
  .handler(routingContext -> {
  RequestParameters params = routingContext.get("parsedParameters");
  RequestParameter awesomeParameter = params.queryParameter("awesomeParameter");
  Integer awesome = awesomeParameter.getInteger();
});

Arrays, objects and serialization styles

User can declare arrays and objects as parameters. The ObjectTypeValidator/ArrayTypeValidator provides the deserialization from string, the validation of objects fields/array items with "nested" validators and the encapsulation inside map/list. For example, you can declare a query parameter as comma separated array of integers like this one: ?q=1,2,3,4,5 and you will receive as result a List<Integer>.

The serialization methods are implemented as subclasses of ContainerDeserializer and there are some prebuilt instances in enum ContainerSerializationStyle. Of course, user can use static methods inside ObjectTypeValidator.ObjectTypeValidatorFactory and ArrayTypeValidator.ArrayTypeValidatorFactory to build this validators, define its serialization style and add the "nested" validators.

HTTPRequestValidationHandler

To start validate the requests, developers can use the HTTPRequestValidationHandler. This class exposes methods to add validators without care about ParameterValidationRule, because they are automatically generated. For every parameter location HTTPRequestValidationHandler exposes three methods:

• add*Param: to add a parameter with type taken from ParameterType enum
• add*ParamWithPattern: to add a string parameter with a pattern
• add*ParamWithCustomTypeValidator: to add a parameter with an instance of ParameterTypeValidator

Then there are methods for body, like addJsonBodySchema or addMultipartRequiredFile

Next time I'm going to introduce you the OAS 3 Router Factory, stay tuned!

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