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data-validation.md

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Data Validation

In this application, we demonstrate an example of data validation to verify a request body for an endpoint. For blockchain applications, the developer should make sure to place the business logic and rules in the chaincode itself. This validation logic is added here as an example in case that there is a need to perform some validation up-front before reaching the chaincode. Other cases include if validation cannot be performed on the chaincode side, such as when using Blockchain Document Store (BDS).

This api-bootstrap provides validation on a data schema for a POST endpoint. This is done by creating middleware which validates the request body, to ensure that the required fields are provided with correct data format, before passing the request to a controller function. This validation makes use of the @hapi/joi npm package which provides simple syntax to create requirements for the data fields and objects.

This api-bootstrap contains an example route /data that leverages the data validation middleware. This route details are provided in the public/swagger.yaml which presents the endpoint on the swagger api when the app is launched. The request body prompted by the endpoint looks like:

{
  "id": "string",
  "stringValue": "string",
  "numValue": 0,
  "date": "2019-09-18T22:21:45.226Z",
  "email": "[email protected]"
}

When the POST /data endpoint is executed, this data schema is routed through the server/routes/data.ts file. The router provides the schema validation middleware and the controller function to land on once validated:

router.post('/', schemaValidations.addData, dataCtrl.default);

This schemaValidations.addData calls the validation for this call in the server/helpers/validation.ts module. Here the schema for the req.body object is defined as thus:

const schema = Joi.object({
    id: Joi.string().trim().max(100).required().label('id'),
    stringValue: Joi.string().trim().required().label('stringValue'),
    numValue: Joi.number().required().label('numValue'),
    dateValue: Joi.date().required().label('dateValue'),
    emailValue: Joi.string().email({ minDomainSegments: 2 }).required().label('emailValue'),
});

This shows the Joi syntax for defining particular fields such as object, string, number, date and email. It marks each field in the object as required for the data body. Joi's data validation library provides validation for multiple type of data attributes. It also allows creating custom validation and updating fields along the way.

This example eventually leads the data to a controller function in server/controllers/data.ts. This function does not make any calls to the blockchain network and returns with statusCode: 200. The developer can add logic here to invoking this data on the blockchain network as they see fit for their application.