OAS Validator

1. Introduction 📖

cpp-oasvalidator is a C++ thread-safe library engineered for the validation of HTTP requests against OpenAPI 3.x specifications. This library can be integrated with REST servers and API gateways to ensure only compliant requests reach your backend services.

With support for OpenAPI 3.x, this library streamlines the process of validating various components of an HTTP request, from methods and routes to detailed parameters and JSON body.

2. Key Features 🌟

  • Efficient, Sequential Validation: Validates requests in a logical order, starting from the HTTP method down to the header parameters. This means if you validate a later stage, preceding steps are validated as well.

  • Thread-Safe: Utilizes thread-safe data structures and methods to ensure concurrent requests are handled without any issues.

  • In-Depth Error Reports: Returns an insightful error enumeration coupled with an extensive error message in JSON format to pinpoint inaccuracies.

  • Optimized Performance: Utilizes lazy deserialization, only processing content when all prior checks pass.

  • Broad Parameter Support: Deserializes parameters across a spectrum of styles and data types, ensuring a wide range of OpenAPI configurations are supported.

Benchmarking results are available here.

3. Validation Sequence 📜

The library validates HTTP requests in the following order:

  1. HTTP Method Validation: Ensures that the HTTP method (GET, POST, PUT, etc.) aligns with the OpenAPI spec.

  2. Route Validation: Checks if the provided route matches the specification.

  3. Body Validation: Validates the JSON body structure and data against the OpenAPI spec.

  4. Path Parameter Validation: Validates path parameters.

  5. Query Parameter Validation: Ensures query parameters are consistent with the OpenAPI spec.

  6. Header Parameter Validation: Confirms headers are in line with the OpenAPI specification.

  7. Request Validation: Validates the whole HTTP request starting from method, route, body (if provided), path/query params (if specified in specs) and/or headers. To address all variations, four overloaded methods are provided.

For a comprehensive understanding, refer to API Reference.

4. Parameter Styles, data types & Deserialization 🛠

cpp-oasvalidator can deserialize and parse parameters of all data types serialized in various styles provided by Swagger/OpenAPI. Following tables provide the details.

4.1 Path Parameters

Style

Explode

Primitive

String

Primitive Array

String Array

Object

simple

false

✅

✅

✅

✅

✅

simple

true

✅

✅

✅

✅

✅

label

false

✅

✅

✅

✅

✅

label

true

✅

✅

✅

✅

✅

matrix

false

✅

✅

✅

✅

✅

matrix

true

✅

✅

✅

✅

✅

* Default serialization method

4.2 Query Parameters

Style

Explode

Primitive

String

Primitive Array

String Array

Object

form

true

✅

✅

✅

✅

✅

form

false

✅

✅

✅

✅

✅

spaceDelimited

true

N/A

N/A

✅

✅

N/A

spaceDelimited

false

N/A

N/A

✅

✅

N/A

pipeDelimited

true

N/A

N/A

✅

✅

N/A

pipeDelimited

false

N/A

N/A

✅

✅

N/A

deepObject

false

N/A

N/A

N/A

N/A

✅

* Default serialization method

4.3 Header Parameters

Style

Explode

Primitive

String

Primitive Array

String Array

Object

simple

false

✅

✅

✅

✅

✅

simple

true

✅

✅

✅

✅

✅

* Default serialization method

5. Error Handling 🚫

cpp-oasvalidator responds with a specific validationError enum value, indicating the error type:

enum class validationError
{
    NONE                 = 0,
    INVALID_METHOD       = -1,
    INVALID_ROUTE        = -2,
    INVALID_PATH_PARAM   = -3,
    INVALID_QUERY_PARAM  = -4,
    INVALID_HEADER_PARAM = -5,
    INVALID_BODY         = -6,
    INVALID_RSP          = -7
};

An accompanying detailed error message, structured in JSON, elucidates the error:

{
   "errorCode": "INVALID_BODY",
   "details": {
      "specRef": "#/paths/%2Ftest%2Fall%2F{param1}%2Fabc%2F{param2}%2F{param3}/post/requestBody/content/application%2Fjson/schema",
      "code": "oneOf",
      "description": "Property did not match any of the sub-schemas specified by 'oneOf', refer to following errors.",
      "instance": "#/field6",
      "schema": "#/properties/field6",
      "errors": [
         {
            "code": "type",
            "description": "Property has a type 'boolean' that is not in the following list: 'integer'.",
            "instance": "#/field6",
            "schema": "#/properties/field6/oneOf/0",
            "context": "oneOf"
         },
         {
            "code": "type",
            "description": "Property has a type 'boolean' that is not in the following list: 'string'.",
            "instance": "#/field6",
            "schema": "#/properties/field6/oneOf/1",
            "context": "oneOf"
         }
      ]
   }
}

6. Getting Started 🚀

6.1 Installation 🔧

Prerequisites:

  • A C++11 compatible compiler.

  • CMake 3.10 or higher.

  • GoogleTest (for tests and code coverage)

  • GCOV (for code covarge report)

  • LCOV (for code covarge report)

Although cpp-oasvalidator utilizes RapidJSON during its build process, the final build is standalone and doesn’t require any additional dependencies at runtime.

6.1.1 Cloning the Repository

To clone the repository, run the following command:

git clone --recursive https://github.com/nawaz1991/cpp-oasvalidator.git

6.1.2 Building and Installing

To build and install cpp-oasvalidator, follow the steps below:

  1. Navigate to the root directory of the project.

  2. Run the following commands:

    cmake -S . -B build
cmake --build build --target oasvalidator -j $(nproc)
cd build
sudo make install

6.2 Running the Tests

To run the tests, follow the steps below: 1. Navigate to the root directory of the project. 2. Run the following commands:

cmake -S . -B build -DBUILD_TESTS=ON
cmake --build build --target oasvalidator-unittests -j $(nproc)
build/test/unittest/oasvalidator-unittests

6.3 Generating Code Coverage Report

To generate the code coverage report, follow the steps below: 1. Navigate to the root directory of the project. 2. Run the following commands:

cmake -S . -B build -DBUILD_TESTS=ON -DBUILD_COVERAGE=ON
cmake --build build --target oasvalidator-unittests -j $(nproc)

The coverage report will be generated in the build/covhtml-cpp-oasvalidator/ directory. Open index.html in your browser to view the report.

6.4 Performance Benchmarking

To run the performance benchmark, follow the steps below:

  1. Navigate to the root directory of cpp-oasvalidator.

  2. Run the following commands:

    cmake -S . -B build -DBUILD_PERF=ON
cmake --build build --target oasvalidator-perftests -j $(nproc)
build/test/perftest/oasvalidator-perftests

6.5 Running the Example

To run the example, follow the steps below:

  1. Navigate to the root directory of cpp-oasvalidator.

  2. Run the following commands:

    cmake -S . -B build -DBUILD_EXAMPLE=ON
cmake --build build --target oasvalidator-example -j $(nproc)
build/example/oasvalidator-example

6.6 Initialization 🎬

To utilize cpp-oasvalidator, include the relevant header and initialize the validator with your OpenAPI specification:

target_link_libraries(<your_target> PRIVATE oasvalidator)

#include <oas_validator.hpp>
OASValidator validator("/path/to/your/spec.json");

Note

The oas_specs can be a file path or a JSON string. If you provide a file path, the library will read the file and parse it. If you provide a JSON string, the library will parse it directly.

Then, utilize the various validation methods to inspect your requests.

7. Conclusion 📜

cpp-oasvalidator is your one-stop solution for rigorous REST request validation against the OpenAPI specification. With its systematic validation order, expansive parameter style support, and meticulous error reporting, it ensures your services stay compliant with your OpenAPI specs.