JSON Schema

It’s often necessary for applications to validate JSON objects, to ensure that required properties are present and that additional constraints (such as a price never being less than one dollar) are met. Validation is typically performed in the context of JSON Schema.

JSON Schema is a grammar language for defining the structure, content, and (to some extent) semantics of JSON objects. It lets you specify metadata (data about data) about what an object’s properties mean and what values are valid for those properties. The result of applying the grammar language is a schema (a blueprint) describing the set of JSON objects that are valid according to the schema.

1. JSON Schema is expressed a schema, which itself is a JSON object.
2. JSON Schema is maintained at http://json-schema.org.
3. It describes your existing data format.
4. If offers clear, human-readable, and machine-readable documentation.
5. It provides complete structural validation, which is useful for automated testing and validating client-submitted data.

JSON schema validation example

Let’s consider the schema is :

{
   "$schema": "http://json-schema.org/draft-04/schema#",
   "title": "Person",
   "description": "A person",
   "type": "object",
   "properties":
   {
      "name":
      {
         "description": "A person's name",
         "type": "string"
      },
      "age":
      {
         "description": "A person's age",
         "type": "number",
         "minimum": 18,
         "maximum": 64
      }                                                                                
   },
   "required": ["name", "age"]    
}

and JSON object is :

{
   "name": "John Doe",
   "age": 35
}

I am using online validator at JSONSchemaLint.

Valid document example

Valid JSON

Invalid document example (age > 64)

Invalid JSON