What is WoT: JSON Schema validators
by the Web of Things Community Group
In the previous three videos, we have shown the features and basic implementations of JSON Schema. In this video, we will look into the actual validation process with programming libraries and examples. The corresponding web page of this video is at https://w3c.github.io/wot-cg/tutorials/whatiswot/docs/preliminary/json-schema/practice-validators.
Video
Transcript
In the previous videos of JSON Schema, we have explained the features and basic implementations of JSON Schema. In this video, we will show the actual validation process with libraries and code examples.
Throughout this video, our main focus will be on validation with the ' jsonschema ' Python library and the 'AJV' JavaScript library, but many other libraries to validate JSON using a JSON Schema exist in different programming languages and tools.
There are many validators. Here are some of the more popular ones.
For further information, you can check the JSON Schema homepage via the link in the video description.
This is the basic validation flow that all libraries follow.
The library takes a schema for your JSON data and validates your data according to the schema. The validation result is output as a boolean.
So let's start with AJV! It is a JavaScript library.
This is the same temperature sensor example we used before. Let’s examine this in JavaScript code.
First, we import the `AJV` library.
This is the Schema that describes the JSON we are expecting.
With this line of code, AJV takes schema as a parameter compiles it to function, and caches it.
This is the data to be validated.
Here we can see the validation step where the result is written into a boolean named isValid.
This step is for printing the result of the validation. If isValid is true, then it prints "JSON input is valid according to Schema". Otherwise, it prints the "JSON input is not valid according to Schema" and the error message.
It outputs that input is valid since the data that we enter suits the predefined schema.
Now let's take a look at the same validation example but with Python's jsonschema library. It is an implementation of the JSON Schema specification for Python.
We will use the same temperature example that we use for AJV but for Python this time.
Let's take a look at the code in detail.
With this line of code, we are importing the function from the library.
This is the same schema in the previous example.
This is the data to be validated.
This validate function takes the data and the schema validates it and prints the result. If the data is valid, it does not print anything. Otherwise, it prints the error message.
The code outputs that the data is not valid since the property "temperatureOf" needs to be string. However, in the given data it is an integer.
This concludes the videos on JSON Schema.
You can proceed to the next tutorial by clicking on the card or the video description.
