Invenio-JSONSchemas¶

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Invenio module for building and serving JSONSchemas.

Further documentation is available on https://invenio-jsonschemas.readthedocs.io/

User’s Guide¶

This part of the documentation will show you how to get started in using Invenio-JSONSchemas.

Installation¶

Invenio-JSONSchemas is on PyPI so all you need is:

$ pip install invenio-jsonschemas

Configuration¶

Default configuration.

invenio_jsonschemas.config.JSONSCHEMAS_ENDPOINT = '/schemas'¶: Default schema endpoint.

invenio_jsonschemas.config.JSONSCHEMAS_HOST = 'localhost'¶: Default json schema host.

invenio_jsonschemas.config.JSONSCHEMAS_LOADER_CLS = None¶: Loader class used in JSONRef when replacing $ref.

invenio_jsonschemas.config.JSONSCHEMAS_REGISTER_ENDPOINTS_API = True¶: Register the endpoints on the API app.

invenio_jsonschemas.config.JSONSCHEMAS_REGISTER_ENDPOINTS_UI = True¶: Register the endpoints on the UI app.

invenio_jsonschemas.config.JSONSCHEMAS_REPLACE_REFS = False¶: Whether to resolve $ref before serving a schema.

invenio_jsonschemas.config.JSONSCHEMAS_RESOLVER_CLS = 'invenio_jsonschemas.utils.resolve_schema'¶

Resolver used to resolve the schema.

if invenio_jsonschemas.config.JSONSCHEMAS_RESOLVE_SCHEMA is True or there is ?resolved=1 parameter on the request the resolver will run over the schema. This can be used for custom schemas resolver.

invenio_jsonschemas.config.JSONSCHEMAS_RESOLVE_SCHEMA = False¶

Whether to resolve schema using the Resolver Class.

If is True, will replace $ref and run the invenio_jsonschemas.config.JSONSCHEMAS_RESOLVER_CLS class before serving a schema.

invenio_jsonschemas.config.JSONSCHEMAS_URL_SCHEME = 'https'¶: Default url scheme for schemas.

Usage¶

Invenio-JSONSchemas is a module for building and serving JSON Schemas.

Using this module one can:

Define JSON Schemas and expose them under a /schemas endpoint.
Validate data using locally defined and/or external JSON Schemas.
Resolve complex schemas and expand their references ($ref) or allOf tags for usage with other libraries that do not support them.

JSON Schema basics¶

Using JSON Schemas is a popular way to define and make publicly available the internal structure of complex entities being used inside an application. Since Invenio is a digital library framework, dealing with entities that contain complex metadata, like for example bibliographic records, is common and if not handled properly can lead to data inconsistencies.

We will not attempt to explain in detail how JSON Schemas are defined and work, since there are much more thorough resources available in the official JSON Schema website. Having a basic knowledge of them though is recommended in order to understand what this module provides on top of them.

Here is a basic JSON Schema defining the structure of a bibliographic record with a title, an optional description, a list of creators and a publication_year:

{
    "$schema": "http://json-schema.org/draft-04/schema#",
    "id": "https://myapp.org/schemas/record.json",
    "type": "object",
    "properties": {
        "title": { "type": "string" },
        "description": { "type": "string" },
        "creators": {
            "type": "array",
            "items": {
                "type": "object",
                "properties": {
                    "name": { "type": "string" }
                },
                "required": ["name"]
            }
        },
        "publication_year": { "type": "integer" }
    },
    "required": ["title", "creators", "publication_year"]
}

A valid record for this JSON Schema would be the following:

{
    "title": "This is a record title",
    "creators": [ { "name": "Doe, John"}, { "name": "Roe, Jane" } ],
    "publication_year": 2018
}

Initialization¶

First create a Flask application:

>>> from flask import Flask
>>> app = Flask(__name__)

Configuration¶

Before we initialize the InvenioJSONSchemas extension, we need to configure which is our application’s host. This will help with automatically skipping additional HTTP requests when fetching locally defined JSON Schemas. More about how this works is described in Composable schemas with JSONRef.

>>> # If your website's host is e.g. "myapp.org"
>>> app.config['JSONSCHEMAS_HOST'] = 'myapp.org'

Last, but not least, let’s initialize the extension:

>>> from invenio_jsonschemas import InvenioJSONSchemas
>>> ext = InvenioJSONSchemas(app)

Setuptools integration¶

The above steps didn’t actually register any JSON Schemas. In order for your JSON Schemas to be registered you must specify in your package’s setup.py an entry point item in the invenio_jsonschemas.schemas group, pointing to a Python module where the actual JSON Schema .json files are placed. Invenio-JSONSchemas then takes care of loading them automatically during application initialization.

By default the extension loads from entrypoint group name invenio_jsonschemas.schemas but you can change that as shown below:

ext = InvenioJSONSchemas(app, entry_point_group=<entrypoint_group_name>)

Registering JSON Schemas¶

Here is a directory structure containing two JSON Schemas, biology/animal_record_schema.json and record_schema.json, taken from this module’s example application:

$ tree --dirsfirst invenio-jsonschemas/examples/samplepkg

invenio-jsonschemas/examples/samplepkg
├── samplepkg
│   ├── jsonschemas
│   │   ├── biology
│   │   │   └── animal_record_schema.json
│   │   ├── __init__.py
│   │   └── record_schema.json
│   └── __init__.py
└── setup.py

The first thing in order to use invenio_jsonschemas is to register your folder that holds your schemas. To do so you have to include the entrypoint to your package that points to your schema folder as shown below:

# invenio-jsonschemas/examples/samplepkg/setup.py
...
entry_points={
    'invenio_jsonschemas.schemas': [
        'samplepkg = samplepkg.jsonschemas'  # path to your schema folder
    ],
},
...

After registering your schemas folder the extension knows where to find your schemas and how to load them. The extension loads every schema that is under {JSONSCHEMAS_HOST}/{JSONSCHEMAS_ENDPOINT} by fetching it locally and not making a network request. This means that reads directly the file of your schema. Also, the same happens if you have inside of your schema a $ref field pointing to the same url format. You can see the function called when the schema url is requested here.

Exposing JSON Schemas¶

You can enable/disable the endpoint that serves your schemas during the initialization of InvenioJsonSchemas extension by passing the parameter register_config_blueprint. This parameter points to your configuration variable that controls the serving of the schemas. So, if you want to disable the schemas serving you can do it as shown below:

Also by default the schema endpoint will be prefixed by /schemas. If you want to change that you can change the JSONSCHEMAS_ENDPOINT configuration variable. For more available configuration options see the Configuration.

For the above example the two schemas would we available under:

https://myapp.org/schemas/record_schema.json, and
https://myapp.org/schemas/biology/animal_record_schema.json

Composable schemas with JSONRef¶

A JSON Schema can be a fully fleshed out schema, composed of only the “primitive” types provided in the specification, but usually this is impractical when there are sub-entities that are repeated throughout the schema. For that reason JSON Schema provides $ref fields which can point to internal or external schemas. See such an example below:

{
    "$schema": "http://json-schema.org/draft-04/schema#",
    "id": "https://myapp.org/schemas/record.json",
    "definitions": {
        "location": {
            "type": "object",
            "properties": {
                "city": { "stype": "string" },
                "country": { "stype": "string" },
                "address": { "stype": "string" }
            }
        }
    },
    "type": "object",
    "properties": {
        "title": { "type": "string" },
        "creator": { "$ref": "https://foo.org/schemas/person.json" },
        "origin": { "$ref": "#/definitions/location" }
    }
}

Invenio-JSONSchemas provides the ability to serve the fully resolved schema or the compact version including one or many $ref fields. The way to tell the extension to serve the resolved schema is either by passing the querystring parameter refs=1 when fetching a schema or by setting the JSONSCHEMAS_REPLACE_REFS configuration variable to True. Internally the module uses the JsonRef package for resolving the references in the schema.

If you make a request to GET https://myapp.org/schemas/record.json?refs=1, you will get something similar to:

{
    "$schema": "http://json-schema.org/draft-04/schema#",
    "id": "https://myapp.org/schemas/record.json",
    "definitions": { ... },
    "type": "object",
    "properties": {
        "title": { "type": "string" },
        "creator": {
            // person.json schema will be fetched and expanded here
            ...
         },
        "origin": {
            "type": "object",
            "properties": {
                "city": { "stype": "string" },
                "country": { "stype": "string" },
                "address": { "stype": "string" }
            }
        }
    }
}

The module also expands the allOf tags when the resolved=1 querystring parameter is passed or the JSONSCHEMAS_RESOLVE_SCHEMA configuration variable is set to True. A schema example that includes the allOf tag can be shown below:

...
"id": "https://myapp.org/schemas/record.json",
"allOf": [
    { "properties": { "title": { "type": "string" } } },
    { "properties": { "status": { "enum": [ "published", "draft" ] } } }
]
...

If you make a request to GET https://myapp.org/schemas/record.json?resolved=1 you would get a response in the following format:

...
// The "allOf" items have been merged in a single object
"properties": {
    "title": { "type": "string" },
    "status": { "enum": [ "published", "draft" ] }
}
...

Note on storing absolute URLs¶

As discussed in this issue, it is not recommended to store and expose absolute URLs in the $ref, as they can change in the future. One should instead try to use DOI/EPIC or other kind of identifiers with the certitude that they will never change, to avoid broken references.

Using with Invenio-Records¶

Invenio-JSONSchemas includes an invenio_records.jsonresolver entry point item which registers a JSONResolver plugin for Invenio-Records. This basically means that records that are being validated against schemas that include $ref s to locally defined schemas won’t do an HTTP request to fetch these schemas, and resolve them locally. You can read more about record validation in the documentation of Invenio-Records.

Example application¶

Run example development server:

$ pip install -e .[all]
$ cd examples
$ ./app-setup.sh
$ python app.py

Open the schema from web:

$ curl http://localhost:5000/schemas/record_schema.json
$ curl http://localhost:5000/schemas/biology/animal_record_schema.json

Teardown the application:

$ ./app-teardown.sh

API Reference¶

If you are looking for information on a specific function, class or method, this part of the documentation is for you.

API Docs¶

Invenio module for building and serving JSONSchemas.

class invenio_jsonschemas.ext.InvenioJSONSchemas(app=None, **kwargs)[source]¶

Invenio-JSONSchemas extension.

Register blueprint serving registered schemas and can be used as an api to register those schemas.

Note

JSON schemas are served as static files. Thus their “id” and “$ref” fields might not match the Flask application’s host and port.

Extension initialization.

Parameters:	app – The Flask application. (Default: `None`)

init_app(app, entry_point_group=None, register_blueprint=True, register_config_blueprint=None)[source]¶

Flask application initialization.

Parameters:	app – The Flask application. entry_point_group – The group entry point to load extensions. (Default: `invenio_jsonschemas.schemas`) register_blueprint – Register the blueprints. register_config_blueprint – Register blueprint for the specific app from a config variable.

init_config(app)[source]¶: Initialize configuration.

class invenio_jsonschemas.ext.InvenioJSONSchemasAPI(app=None, **kwargs)[source]¶

Invenio-JSONSchemas extension for API.

Extension initialization.

Parameters:	app – The Flask application. (Default: `None`)

init_app(app)[source]¶

Flask application initialization.

Parameters:	app – The Flask application.

class invenio_jsonschemas.ext.InvenioJSONSchemasState(app)[source]¶

InvenioJSONSchemas state and api.

Constructor.

Parameters:	app – application registering this state

get_schema(**kwds)[source]¶

Retrieve a schema.

Parameters:	path – schema’s relative path. with_refs – replace $refs in the schema. resolved – resolve schema using the resolver `invenio_jsonschemas.config.JSONSCHEMAS_RESOLVER_CLS`
Raises:	invenio_jsonschemas.errors.JSONSchemaNotFound – If no schema was found in the specified path.
Returns:	The schema in a dictionary form.

get_schema_dir(path)[source]¶

Retrieve the directory containing the given schema.

Parameters:	path – Schema path, relative to the directory where it was registered.
Raises:	invenio_jsonschemas.errors.JSONSchemaNotFound – If no schema was found in the specified path.
Returns:	The schema directory.

get_schema_path(path)[source]¶

Compute the schema’s absolute path from a schema relative path.

Parameters:	path – relative path of the schema.
Raises:	invenio_jsonschemas.errors.JSONSchemaNotFound – If no schema was found in the specified path.
Returns:	The absolute path.

list_schemas()[source]¶

List all JSON-schema names.

Returns:	list of schema names.
Return type:	list

loader_cls[source]¶: Loader class used in JsonRef.replace_refs.

path_to_url(path)[source]¶

Build URL from a path.

Parameters:	path – relative path of the schema.
Returns:	The schema complete URL or `None` if not found.

register_schema(directory, path)[source]¶

Register a json-schema.

Parameters:	directory – root directory path. path – schema path, relative to the root directory.

register_schemas_dir(directory)[source]¶

Recursively register all json-schemas in a directory.

Parameters:	directory – directory path.

resolver_cls[source]¶: Loader to resolve the schema.

url_to_path(url)[source]¶

Convert schema URL to path.

Parameters:	url – The schema URL.
Returns:	The schema path or `None` if the schema can’t be resolved.

class invenio_jsonschemas.ext.InvenioJSONSchemasUI(app=None, **kwargs)[source]¶

Invenio-JSONSchemas extension for UI.

Extension initialization.

Parameters:	app – The Flask application. (Default: `None`)

init_app(app)[source]¶

Flask application initialization.

Parameters:	app – The Flask application.

Errors¶

Invenio-JSONSchemas errors.

exception invenio_jsonschemas.errors.JSONSchemaDuplicate(schema, first_dir, second_dir, *args, **kwargs)[source]¶

Exception raised when multiple schemas match the same path.

Constructor.

Parameters:	schema – duplicate schema path. first_dir – first directory where the schema was found. second_dir – second directory where the schema was found.

exception invenio_jsonschemas.errors.JSONSchemaError[source]¶: Base class for errors in Invenio-JSONSchemas module.

exception invenio_jsonschemas.errors.JSONSchemaNotFound(schema, *args, **kwargs)[source]¶

Exception raised when a requested JSONSchema is not found.

Constructor.

Parameters:	schema – path of the requested schema which was not found.

JSON resolver¶

JSON resolver for JSON schemas.

invenio_jsonschemas.jsonresolver.jsonresolver_loader(url_map)[source]¶

JSON resolver plugin that loads the schema endpoint.

Injected into Invenio-Records JSON resolver.

Views¶

Invenio module for building and serving JSONSchemas.

invenio_jsonschemas.views.create_blueprint(state)[source]¶

Create blueprint serving JSON schemas.

Parameters:	state – `invenio_jsonschemas.ext.InvenioJSONSchemasState` instance used to retrieve the schemas.

Utils¶

Invenio JSONSchemas utils.

invenio_jsonschemas.utils.resolve_schema(schema)[source]¶

Transform JSON schemas “allOf”.

This is the default schema resolver.

This function was created because some javascript JSON Schema libraries don’t support “allOf”. We recommend to use this function only in this specific case.

This function is transforming the JSON Schema by removing “allOf” keywords. It recursively merges the sub-schemas as dictionaries. The process is completely custom and works only for simple JSON Schemas which use basic types (object, string, number, …). Optional structures like “schema dependencies” or “oneOf” keywords are not supported.

Parameters:	schema (dict) – the schema to resolve.
Returns:	the resolved schema

Note

The schema should have the $ref already resolved before running this method.

Additional Notes¶

Notes on how to contribute, legal information and changes are here for the interested.

Contributing¶

Contributions are welcome, and they are greatly appreciated! Every little bit helps, and credit will always be given.

Types of Contributions¶

Report Bugs¶

Report bugs at https://github.com/inveniosoftware/invenio-jsonschemas/issues.

If you are reporting a bug, please include:

Your operating system name and version.
Any details about your local setup that might be helpful in troubleshooting.
Detailed steps to reproduce the bug.

Fix Bugs¶

Look through the GitHub issues for bugs. Anything tagged with “bug” is open to whoever wants to implement it.

Implement Features¶

Look through the GitHub issues for features. Anything tagged with “feature” is open to whoever wants to implement it.

Write Documentation¶

Invenio-JSONSchemas could always use more documentation, whether as part of the official Invenio-JSONSchemas docs, in docstrings, or even on the web in blog posts, articles, and such.

Submit Feedback¶

The best way to send feedback is to file an issue at https://github.com/inveniosoftware/invenio-jsonschemas/issues.

If you are proposing a feature:

Explain in detail how it would work.
Keep the scope as narrow as possible, to make it easier to implement.
Remember that this is a volunteer-driven project, and that contributions are welcome :)

Get Started!¶

Ready to contribute? Here’s how to set up invenio-jsonschemas for local development.

Fork the inveniosoftware/invenio-jsonschemas repo on GitHub.

Clone your fork locally:

$ git clone git@github.com:your_name_here/invenio-jsonschemas.git

Install your local copy into a virtualenv. Assuming you have virtualenvwrapper installed, this is how you set up your fork for local development:
```
$ mkvirtualenv invenio-jsonschemas
$ cd invenio-jsonschemas/
$ pip install -e .[all]
```
Create a branch for local development:
```
$ git checkout -b name-of-your-bugfix-or-feature
```
Now you can make your changes locally.
When you’re done making changes, check that your changes pass tests:
```
$ ./run-tests.sh
```
The tests will provide you with test coverage and also check PEP8 (code style), PEP257 (documentation), flake8 as well as build the Sphinx documentation and run doctests.

Commit your changes and push your branch to GitHub:

$ git add .
$ git commit -s
    -m "component: title without verbs"
    -m "* NEW Adds your new feature."
    -m "* FIX Fixes an existing issue."
    -m "* BETTER Improves and existing feature."
    -m "* Changes something that should not be visible in release notes."
$ git push origin name-of-your-bugfix-or-feature

Submit a pull request through the GitHub website.

Pull Request Guidelines¶

Before you submit a pull request, check that it meets these guidelines:

The pull request should include tests and must not decrease test coverage.
If the pull request adds functionality, the docs should be updated. Put your new functionality into a function with a docstring.
The pull request should work for Python 2.7 and 3.5. Check https://travis-ci.org/inveniosoftware/invenio-jsonschemas/pull_requests and make sure that the tests pass for all supported Python versions.

Changes¶

Version 1.0.0 (released 2018-03-23)

Initial public release.

License¶

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Note

In applying this license, CERN does not waive the privileges and immunities granted to it by virtue of its status as an Intergovernmental Organization or submit itself to any jurisdiction.

Contributors¶

Alexander Ioannidis
Alizee Pace
Chiara Bigarella
Chris Aslanoglou
Diego Rodriguez
Harris Tzovanakis
Jacopo Notarstefano
Javier Martin Montull
Jiri Kuncar
Krzysztof Nowak
Lars Holm Nielsen
Leonardo Rossi
Marco Neumann
Nicolas Harraudeau
Paulina Lach
Robin Schroer
Sami Hiltunen
Sebastian Witowski
Tibor Simko

Invenio-JSONSchemas¶

User’s Guide¶

Installation¶

Configuration¶

Usage¶

JSON Schema basics¶

Initialization¶

Configuration¶

Setuptools integration¶

Registering JSON Schemas¶

Exposing JSON Schemas¶

Composable schemas with JSONRef¶

Note on storing absolute URLs¶

Using with Invenio-Records¶

Example application¶

API Reference¶

API Docs¶

Errors¶

JSON resolver¶

Views¶

Utils¶

Additional Notes¶

Contributing¶

Types of Contributions¶

Report Bugs¶

Fix Bugs¶

Implement Features¶

Write Documentation¶

Submit Feedback¶

Get Started!¶

Pull Request Guidelines¶

Changes¶

License¶

Contributors¶

Invenio-JSONSchemas

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