The RestAPI

Since version 19.5.10 pyDAL includes a restful API [CIT0801] called RestAPI. It is inspired by GraphQL [CIT0802] and while it’s not quite the same due to it being less powerful, it is in the spirit of py4web since it’s more practical and easier to use.

Like GraphQL RestAPI allows a client to query for information using the GET method and allows to specify some details about the format of the response (which references to follow, and how to denormalize the data). Unlike GraphQL it allows the server to specify a policy and restrict which queries are allowed and which ones are not. They can be evaluated dynamically per request based on the user and the state of the server.

As the name implies RestAPI allows all standard methods: GET, POST, PUT, and DELETE. Each of them can be enabled or disabled based on the policy, for individual tables and individual fields.

Nota

Specifications might be subject to changes since this is a new feature.

In the examples below we assume a simple app called “superheroes”:

# in superheroes/__init__.py
import os
from py4web import action, request, Field, DAL
from pydal.restapi import RestAPI, Policy

# database definition
DB_FOLDER = os.path.join(os.path.dirname(__file__), 'databases')
if not os.path.isdir(DB_FOLDER):
    os.mkdir(DB_FOLDER)
db = DAL('sqlite://storage.sqlite', folder=DB_FOLDER)
db.define_table(
    'person',
    Field('name'),
    Field('job'))
db.define_table(
    'superhero',
    Field('name'),
    Field('real_identity', 'reference person'))
db.define_table(
    'superpower',
    Field('description'))
db.define_table(
    'tag',
    Field('superhero', 'reference superhero'),
    Field('superpower', 'reference superpower'),
    Field('strength', 'integer'))

# add example entries in db
if not db(db.person).count():
    db.person.insert(name='Clark Kent', job='Journalist')
    db.person.insert(name='Peter Park', job='Photographer')
    db.person.insert(name='Bruce Wayne', job='CEO')
    db.superhero.insert(name='Superman', real_identity=1)
    db.superhero.insert(name='Spiderman', real_identity=2)
    db.superhero.insert(name='Batman', real_identity=3)
    db.superpower.insert(description='Flight')
    db.superpower.insert(description='Strength')
    db.superpower.insert(description='Speed')
    db.superpower.insert(description='Durability')
    db.tag.insert(superhero=1, superpower=1, strength=100)
    db.tag.insert(superhero=1, superpower=2, strength=100)
    db.tag.insert(superhero=1, superpower=3, strength=100)
    db.tag.insert(superhero=1, superpower=4, strength=100)
    db.tag.insert(superhero=2, superpower=2, strength=50)
    db.tag.insert(superhero=2, superpower=3, strength=75)
    db.tag.insert(superhero=2, superpower=4, strength=10)
    db.tag.insert(superhero=3, superpower=2, strength=80)
    db.tag.insert(superhero=3, superpower=3, strength=20)
    db.tag.insert(superhero=3, superpower=4, strength=70)
    db.commit()

# policy definitions
policy = Policy()
policy.set('superhero', 'GET', authorize=True, allowed_patterns=['*'])
policy.set('*', 'GET', authorize=True, allowed_patterns=['*'])

# for security reasons we disabled here all methods but GET at the policy level,
# to enable any of them just set authorize = True
policy.set('*', 'PUT', authorize=False)
policy.set('*', 'POST', authorize=False)
policy.set('*', 'DELETE', authorize=False)

@action('api/<tablename>/', method = ['GET', 'POST'])
@action('api/<tablename>/<rec_id>', method = ['GET', 'PUT', 'DELETE'])
@action.uses(db)
def api(tablename, rec_id=None):
    return RestAPI(db, policy)(request.method,
                            tablename,
                            rec_id,
                            request.GET,
                            request.POST
                            )

@action("index")
def index():
    return "RestAPI example"

RestAPI policies and actions

The policy is per table (or * for all tables) and per method. authorize can be True (allow), False (deny) or a function with the signature (method, tablename, record_id, get_vars, post_vars) which returns True/False. For the GET policy one can specify a list of allowed query patterns (* for all). A query pattern will be matched against the keys in the query string.

A acção acima referida é exposto como:

/superheroes/api/{tablename}
/superheroes/api/{tablename}/{rec_id}

The result can be seen directly with a browser, rendered as JSON. Let’s look for example at the person table:

_images/restapi.png

The diagram of the superhero’s database should help you interpreting the code:

_images/restapi2.png

Nota

Keep in mind that request.POST only contains the form data that is posted using a regular HTML-form or JavaScript FormData object. If you post just plain object (e.g. axios.post('path/to/api', {field:'some'})) you should pass request.json instead of request.POST, since the latter will contain just raw request-body which is string, not JSON. See Bottle documentation about request object.

RestAPI GET

A consulta geral tem a forma `` {} algo .eq = value`` onde `` eq = `` significa “igual”, `` gt = `` significa “maior que”, etc. A expressão pode ser prefixado por `` not.``.

{something} can be:

  • the name of a field in the table being queried as in:

    ** Todos os super-heróis chamado de “Superman” **

    /superheroes/api/superhero?name.eq=Superman
    
  • the name of a field of a table referred by the table being queried as in:

    ** Todos os super-heróis com a identidade real “Clark Kent” **

    /superheroes/api/superhero?real_identity.name.eq=Clark Kent
    
  • the name of a field of a table that refers to the table being queried as in:

    ** Todos os super-heróis com qualquer superpotência tag com força> 90 **

    /superheroes/api/superhero?superhero.tag.strength.gt=90
    

    (here tag is the name of the link table, the preceding superhero is the name of the field that refers to the selected table and strength is the name of the field used to filter)

  • a field of the table referenced by a many-to-many linked table as in:

    ** Todos os super-heróis com o poder de vôo **

    /superheroes/api/superhero?superhero.tag.superpower.description.eq=Flight
    

Dica

The key to understand the syntax above is to read it as:

<< select records of table superhero referred by field superhero of table tag, when the superpower field of said table points to a record with description equal to “Flight” >>

The query allows additional modifiers for example:

@offset=10
@limit=10
@order=name
@model=true
@lookup=real_identity

The first 3 are obvious. @model returns a JSON description of database model. @lookup denormalizes the linked field.

RestAPI practical examples

Aqui estão alguns exemplos práticos:

URL:

/superheroes/api/superhero

RESULTADO:

{
    "count": 3,
    "status": "success",
    "code": 200,
    "items": [
        {
            "real_identity": 1,
            "name": "Superman",
            "id": 1
        },
        {
            "real_identity": 2,
            "name": "Spiderman",
            "id": 2
        },
        {
            "real_identity": 3,
            "name": "Batman",
            "id": 3
        }
    ],
    "timestamp": "2019-05-19T05:38:00.132635",
    "api_version": "0.1"
}

URL:

/superheroes/api/superhero?@model=true

RESULTADO:

{
    "count": 3,
    "status": "success",
    "code": 200,
    "items": [
        {
            "real_identity": 1,
            "name": "Superman",
            "id": 1
        },
        {
            "real_identity": 2,
            "name": "Spiderman",
            "id": 2
        },
        {
            "real_identity": 3,
            "name": "Batman",
            "id": 3
        }
    ],
    "timestamp": "2021-01-04T07:03:38.466030",
    "model": [
        {
            "regex": "[1-9]\\d*",
            "name": "id",
            "default": null,
            "required": false,
            "label": "Id",
            "post_writable": true,
            "referenced_by": [
                "tag.superhero"
            ],
            "unique": false,
            "type": "id",
            "options": null,
            "put_writable": true
        },
        {
            "regex": null,
            "name": "name",
            "default": null,
            "required": false,
            "label": "Name",
            "post_writable": true,
            "unique": false,
            "type": "string",
            "options": null,
            "put_writable": true
        },
        {
            "regex": null,
            "name": "real_identity",
            "default": null,
            "required": false,
            "label": "Real Identity",
            "post_writable": true,
            "references": "person",
            "unique": false,
            "type": "reference",
            "options": null,
            "put_writable": true
        }
    ],
    "api_version": "0.1"
}

URL:

/superheroes/api/superhero?@lookup=real_identity

RESULTADO:

{
    "count": 3,
    "status": "success",
    "code": 200,
    "items": [
        {
            "real_identity": {
                "name": "Clark Kent",
                "job": "Journalist",
                "id": 1
            },
            "name": "Superman",
            "id": 1
        },
        {
            "real_identity": {
                "name": "Peter Park",
                "job": "Photographer",
                "id": 2
            },
            "name": "Spiderman",
            "id": 2
        },
        {
            "real_identity": {
                "name": "Bruce Wayne",
                "job": "CEO",
                "id": 3
            },
            "name": "Batman",
            "id": 3
        }
    ],
    "timestamp": "2019-05-19T05:38:00.178974",
    "api_version": "0.1"
}

URL:

/superheroes/api/superhero?@lookup=identity:real_identity

(Desnormalizar o real_identity e renomeá-lo de identidade)

RESULTADO:

{
    "count": 3,
    "status": "success",
    "code": 200,
    "items": [
        {
            "real_identity": 1,
            "name": "Superman",
            "id": 1,
            "identity": {
                "name": "Clark Kent",
                "job": "Journalist",
                "id": 1
            }
        },
        {
            "real_identity": 2,
            "name": "Spiderman",
            "id": 2,
            "identity": {
                "name": "Peter Park",
                "job": "Photographer",
                "id": 2
            }
        },
        {
            "real_identity": 3,
            "name": "Batman",
            "id": 3,
            "identity": {
                "name": "Bruce Wayne",
                "job": "CEO",
                "id": 3
            }
        }
    ],
    "timestamp": "2019-05-19T05:38:00.123218",
    "api_version": "0.1"
}

URL:

/superheroes/api/superhero?@lookup=identity!:real_identity[name,job]

(Desnormalizar o real_identity [mas apenas campos nome e trabalho], recolher a com o prefixo de identidade)

RESULTADO:

{
    "count": 3,
    "status": "success",
    "code": 200,
    "items": [
        {
            "name": "Superman",
            "identity.job": "Journalist",
            "identity.name": "Clark Kent",
            "id": 1
        },
        {
            "name": "Spiderman",
            "identity.job": "Photographer",
            "identity.name": "Peter Park",
            "id": 2
        },
        {
            "name": "Batman",
            "identity.job": "CEO",
            "identity.name": "Bruce Wayne",
            "id": 3
        }
    ],
    "timestamp": "2021-01-04T07:03:38.559918",
    "api_version": "0.1"
}

URL:

/superheroes/api/superhero?@lookup=superhero.tag

RESULTADO:

{
    "count": 3,
    "status": "success",
    "code": 200,
    "items": [
        {
            "real_identity": 1,
            "name": "Superman",
            "superhero.tag": [
                {
                    "strength": 100,
                    "superhero": 1,
                    "id": 1,
                    "superpower": 1
                },
                {
                    "strength": 100,
                    "superhero": 1,
                    "id": 2,
                    "superpower": 2
                },
                {
                    "strength": 100,
                    "superhero": 1,
                    "id": 3,
                    "superpower": 3
                },
                {
                    "strength": 100,
                    "superhero": 1,
                    "id": 4,
                    "superpower": 4
                }
            ],
            "id": 1
        },
        {
            "real_identity": 2,
            "name": "Spiderman",
            "superhero.tag": [
                {
                    "strength": 50,
                    "superhero": 2,
                    "id": 5,
                    "superpower": 2
                },
                {
                    "strength": 75,
                    "superhero": 2,
                    "id": 6,
                    "superpower": 3
                },
                {
                    "strength": 10,
                    "superhero": 2,
                    "id": 7,
                    "superpower": 4
                }
            ],
            "id": 2
        },
        {
            "real_identity": 3,
            "name": "Batman",
            "superhero.tag": [
                {
                    "strength": 80,
                    "superhero": 3,
                    "id": 8,
                    "superpower": 2
                },
                {
                    "strength": 20,
                    "superhero": 3,
                    "id": 9,
                    "superpower": 3
                },
                {
                    "strength": 70,
                    "superhero": 3,
                    "id": 10,
                    "superpower": 4
                }
            ],
            "id": 3
        }
    ],
    "timestamp": "2019-05-19T05:38:00.201988",
    "api_version": "0.1"
}

URL:

/superheroes/api/superhero?@lookup=superhero.tag.superpower

RESULTADO:

{
    "count": 3,
    "status": "success",
    "code": 200,
    "items": [
        {
            "real_identity": 1,
            "name": "Superman",
            "superhero.tag.superpower": [
                {
                    "strength": 100,
                    "superhero": 1,
                    "id": 1,
                    "superpower": {
                        "id": 1,
                        "description": "Flight"
                    }
                },
                {
                    "strength": 100,
                    "superhero": 1,
                    "id": 2,
                    "superpower": {
                        "id": 2,
                        "description": "Strength"
                    }
                },
                {
                    "strength": 100,
                    "superhero": 1,
                    "id": 3,
                    "superpower": {
                        "id": 3,
                        "description": "Speed"
                    }
                },
                {
                    "strength": 100,
                    "superhero": 1,
                    "id": 4,
                    "superpower": {
                        "id": 4,
                        "description": "Durability"
                    }
                }
            ],
            "id": 1
        },
        {
            "real_identity": 2,
            "name": "Spiderman",
            "superhero.tag.superpower": [
                {
                    "strength": 50,
                    "superhero": 2,
                    "id": 5,
                    "superpower": {
                        "id": 2,
                        "description": "Strength"
                    }
                },
                {
                    "strength": 75,
                    "superhero": 2,
                    "id": 6,
                    "superpower": {
                        "id": 3,
                        "description": "Speed"
                    }
                },
                {
                    "strength": 10,
                    "superhero": 2,
                    "id": 7,
                    "superpower": {
                        "id": 4,
                        "description": "Durability"
                    }
                }
            ],
            "id": 2
        },
        {
            "real_identity": 3,
            "name": "Batman",
            "superhero.tag.superpower": [
                {
                    "strength": 80,
                    "superhero": 3,
                    "id": 8,
                    "superpower": {
                        "id": 2,
                        "description": "Strength"
                    }
                },
                {
                    "strength": 20,
                    "superhero": 3,
                    "id": 9,
                    "superpower": {
                        "id": 3,
                        "description": "Speed"
                    }
                },
                {
                    "strength": 70,
                    "superhero": 3,
                    "id": 10,
                    "superpower": {
                        "id": 4,
                        "description": "Durability"
                    }
                }
            ],
            "id": 3
        }
    ],
    "timestamp": "2019-05-19T05:38:00.322494",
    "api_version": "0.1"
}

URL (it’s a single line, split for readability):

/superheroes/api/superhero?
@lookup=powers:superhero.tag[strength].superpower[description]

RESULTADO:

{
    "count": 3,
    "status": "success",
    "code": 200,
    "items": [
        {
            "real_identity": 1,
            "name": "Superman",
            "powers": [
                {
                    "strength": 100,
                    "superpower": {
                        "description": "Flight"
                    }
                },
                {
                    "strength": 100,
                    "superpower": {
                        "description": "Strength"
                    }
                },
                {
                    "strength": 100,
                    "superpower": {
                        "description": "Speed"
                    }
                },
                {
                    "strength": 100,
                    "superpower": {
                        "description": "Durability"
                    }
                }
            ],
            "id": 1
        },
        {
            "real_identity": 2,
            "name": "Spiderman",
            "powers": [
                {
                    "strength": 50,
                    "superpower": {
                        "description": "Strength"
                    }
                },
                {
                    "strength": 75,
                    "superpower": {
                        "description": "Speed"
                    }
                },
                {
                    "strength": 10,
                    "superpower": {
                        "description": "Durability"
                    }
                }
            ],
            "id": 2
        },
        {
            "real_identity": 3,
            "name": "Batman",
            "powers": [
                {
                    "strength": 80,
                    "superpower": {
                        "description": "Strength"
                    }
                },
                {
                    "strength": 20,
                    "superpower": {
                        "description": "Speed"
                    }
                },
                {
                    "strength": 70,
                    "superpower": {
                        "description": "Durability"
                    }
                }
            ],
            "id": 3
        }
    ],
    "timestamp": "2019-05-19T05:38:00.309903",
    "api_version": "0.1"
}

URL (it’s a single line, split for readability):

/superheroes/api/superhero?
@lookup=powers!:superhero.tag[strength].superpower[description]

RESULTADO:

{
    "count": 3,
    "status": "success",
    "code": 200,
    "items": [
        {
            "real_identity": 1,
            "name": "Superman",
            "powers": [
                {
                    "strength": 100,
                    "description": "Flight"
                },
                {
                    "strength": 100,
                    "description": "Strength"
                },
                {
                    "strength": 100,
                    "description": "Speed"
                },
                {
                    "strength": 100,
                    "description": "Durability"
                }
            ],
            "id": 1
        },
        {
            "real_identity": 2,
            "name": "Spiderman",
            "powers": [
                {
                    "strength": 50,
                    "description": "Strength"
                },
                {
                    "strength": 75,
                    "description": "Speed"
                },
                {
                    "strength": 10,
                    "description": "Durability"
                }
            ],
            "id": 2
        },
        {
            "real_identity": 3,
            "name": "Batman",
            "powers": [
                {
                    "strength": 80,
                    "description": "Strength"
                },
                {
                    "strength": 20,
                    "description": "Speed"
                },
                {
                    "strength": 70,
                    "description": "Durability"
                }
            ],
            "id": 3
        }
    ],
    "timestamp": "2019-05-19T05:38:00.355181",
    "api_version": "0.1"
}

URL (it’s a single line, split for readability):

/superheroes/api/superhero?
@lookup=powers!:superhero.tag[strength].superpower[description],
identity!:real_identity[name]

RESULTADO:

{
    "count": 3,
    "status": "success",
    "code": 200,
    "items": [
        {
            "name": "Superman",
            "identity.name": "Clark Kent",
            "powers": [
                {
                    "strength": 100,
                    "description": "Flight"
                },
                {
                    "strength": 100,
                    "description": "Strength"
                },
                {
                    "strength": 100,
                    "description": "Speed"
                },
                {
                    "strength": 100,
                    "description": "Durability"
                }
            ],
            "id": 1
        },
        {
            "name": "Spiderman",
            "identity.name": "Peter Park",
            "powers": [
                {
                    "strength": 50,
                    "description": "Strength"
                },
                {
                    "strength": 75,
                    "description": "Speed"
                },
                {
                    "strength": 10,
                    "description": "Durability"
                }
            ],
            "id": 2
        },
        {
            "name": "Batman",
            "identity.name": "Bruce Wayne",
            "powers": [
                {
                    "strength": 80,
                    "description": "Strength"
                },
                {
                    "strength": 20,
                    "description": "Speed"
                },
                {
                    "strength": 70,
                    "description": "Durability"
                }
            ],
            "id": 3
        }
    ],
    "timestamp": "2021-01-04T07:31:34.974953",
    "api_version": "0.1"
}

URL:

/superheroes/api/superhero?name.eq=Superman

RESULTADO:

{
    "count": 1,
    "status": "success",
    "code": 200,
    "items": [
        {
            "real_identity": 1,
            "name": "Superman",
            "id": 1
        }
    ],
    "timestamp": "2019-05-19T05:38:00.405515",
    "api_version": "0.1"
}

URL:

/superheroes/api/superhero?real_identity.name.eq=Clark Kent

RESULTADO:

{
    "count": 1,
    "status": "success",
    "code": 200,
    "items": [
        {
            "real_identity": 1,
            "name": "Superman",
            "id": 1
        }
    ],
    "timestamp": "2019-05-19T05:38:00.366288",
    "api_version": "0.1"
}

URL:

/superheroes/api/superhero?not.real_identity.name.eq=Clark Kent

RESULTADO:

{
    "count": 2,
    "status": "success",
    "code": 200,
    "items": [
        {
            "real_identity": 2,
            "name": "Spiderman",
            "id": 2
        },
        {
            "real_identity": 3,
            "name": "Batman",
            "id": 3
        }
    ],
    "timestamp": "2019-05-19T05:38:00.451907",
    "api_version": "0.1"
}

URL:

/superheroes/api/superhero?superhero.tag.superpower.description=Flight

RESULTADO:

{
    "count": 1,
    "status": "success",
    "code": 200,
    "items": [
        {
            "real_identity": 1,
            "name": "Superman",
            "id": 1
        }
    ],
    "timestamp": "2019-05-19T05:38:00.453020",
    "api_version": "0.1"
}

The RestAPI response

All RestAPI response have the fields:

api_version

RestAPI version.

timestamp

Datetime in ISO 8601 format.

status

RestAPI status (i.e. «success» or «error»).

code

HTTP status.

Other optional fields are:

count

Total matching (not total returned), for GET.

items

In response to a GET.

errors

Usually a validation error.

models

Usually if status != «success».

message

For error details.

CIT0801

https://en.wikipedia.org/wiki/Representational_state_transfer

CIT0802

https://graphql.org/