JSON Schema

One of the core features of Gravity is that it's largely based around passing and storing data in JSON format. The JSON messages and storage files must follow a particular schema for them to be valid and read by the program.

We define these schemas within the schema/ folder (singular) and then use a validation module within the code to make sure that all information conforms to the schema. Two related but distinct things live there today:

schema/message.schema, schema/blog.schema, schema/contacts.schema, schema/users.schema, etc. — validated the way this doc describes below, via jsonschema/app/messaging/schema.py.
schema/blocks/*.json and schema/events/ — the Visual Editor's block-type field contracts (see docs/gravity/architecture.md §6 and docs/gravity/visual_editor_design.md), a related but simpler field-definition format, not validated via the jsonschema package.

JSON Schema Validation

To validate a JSON config file from the command line, we can use the jsonschema program. Any time a new message or command is added to a JSON message, the schema file should be updated. This allows us to keep track of the format of our messages, and also allows us to validate that messages passing through the system conform to the JSON schema.

$ jsonschema -i config.json config.schema

JSON Schema Validation Inside of Gravity Python Code

Gravity uses the 'jsonschema' module to validate json messages against a defined schema file that we have defined.

JSON Schema Documentation

To install via pip:

$ pip install jsonschema

When you wish to use the jsonschema validation inside of the code, you will need to include:

from jsonschema import validate