wiki:S3REST

Version 27 (modified by Fran Boon, 12 years ago) ( diff )

Update for new nomenclature

S3REST and XRequest

s3rest

s3rest is a callable global object which implements the RESTful interface for the S3 framework. This interface can be configured dynamically, and can easily be used to build RESTful controllers throughout the application.

Important: an s3rest instance is created per request and must not be stored or referenced by static objects to avoid memory leaks!

The default method handlers implement CRUD (create, read, update, delete) in all major representations, including the capabilities of S3XRC to use in-line XSLT for export and import of XML and JSON formats.

s3rest is an instance of the RESTController class, implemented in modules/s3rest.py.

Instead of the web2py request object, s3rest uses the S3Request class (described below) to represent the current REST request. Other than web2py/request, the XRequest of the current call is not a global object, but gets passed as argument when calling REST method handlers.

REST Methods

It is critical to understand how RESTful requests work.

A RESTful requests has two components:

  • the URL addresses the resource
  • the HTTP method determines the action to be taken with that resource, which is either of:
    • GET, PUT, POST or DELETE

A resource in this terminology is either of:

  • a database table or one or more records in that table
  • a combination of tables or records (so called "compound" or "joined" resources)
  • a function in the application related to one of the above resource types

Functions as resources in RESTful requests are to be understood and addressed as "sub"-resources of their respective primary resource.

The finally executed response action depends on the HTTP/method and on the type of resource addressed by the URL, e.g.

  • if the method is "GET" and the resource addressed is a database table, then the response will be a list of the records in that table
  • if the method is "PUT" and the resource addressed is a record in a table, then the response will be an update of that record with the data from the request body

CRUD Method Handlers

The default method handlers for each of CRUD+S are implemented in models/01_crud.py:

  • shn_read(jr, attr)
  • shn_list(jr, attr)
  • shn_create(jr, attr)
  • shn_update(jr, attr)
  • shn_delete(jr, attr)
  • shn_search(jr, attr)
  • shn_options(jr, attr)
  • import_xml(jr, attr)
  • import_json(jr, attr)

where jr is the current S3Request, and attr contains all further arguments passed to the REST controller.

You can override these defaults at any time by

s3rest.set_handler(action, handler)

where:

  • action is the name of the action, i.e. one of 'read', 'list', 'create', 'update', 'delete', 'search', 'options', 'import_xml' or 'import_json'
  • handler is the handler function/lambda

Custom Methods

You can also add resource-specific custom methods by:

  s3xrc.model.set_method(module, resource, method, action)

where:

  • module is the module prefix of a resource
  • resource is the name of the resource (without prefix)
  • method is a string representing the name of the method (e.g. "search_simple")
  • action is the method handler function/lambda

The action method has to take the same arguments as the default handlers: jr (S3Request) and attr.

S3Request

Important: S3Request instances are generated per request and must not be stored or referenced by static or global objects to avoid memory leaks!

Attributes of the S3Request

The following attributes are set during initialisation of an S3Request object, no further call is required.

Controller Attributes

rcthe resource controller object (S3XRC)
requestthe original web2py request (Storage)
sessionthe current session (Storage)

Request Attributes

representationthe current representation of this request (string, lowercase)
httpthe HTTP method of this request (string, always uppercase!)
extensionthe extension found in the original request (string, lowercase)
methodthe method of the request if not HTTP (string, always lowercase)
custom_actionthe custom method handler for the request (function or lambda)

Primary Resource Attributes

prefixthe prefix (=module name) of the requested resource (string)
namethe name of the requested resource, without prefix (string)
tablenamethe name of the primary table (string)
tablethe primary table (Table)
idthe ID of the primary record (int)
recordthe primary record (Row)

Component Resource Attributes

componentthe requested component, if any (ObjectComponent)
pkeythe primary key of the Resource/Component join (string)
fkeythe foreign key of the Resource/Component join (string)
component_namethe name of the component without prefix (string)
component_idthe ID of the component record as of the request, if any (int)
multipleFlag indicating that multiple component records are allowed (boolean)

Error Indicators

errorthe last error message (string)
invalidFlag indicating this request as invalid (boolean)
badmethodFlag indicating a bad method error (boolean)
badrecordFlag indicating a invalid record ID error (boolean)
badrequestFlag indicating an unqualified request error (boolean)

ObjectComponent contains:

  • prefix, name, table_name, table and attr of the component
  • attr contains:
    • multiple Multiple-flag
    • editable, deletable and listadd
    • list_fields, rss, main and extra
    • onaccept, onvalidation, delete_onaccept and delete_onvalidation
  • methods: set_attr() and get_attr()

Methods of the S3Request

here(representation=None)

  • returns the URL of the current request

there(representation=None)

  • returns the URL of a HTTP GET request for the same resource

same(representation=None)

  • returns the URL of the current request with the primary record ID replaced by the string literal '[id]'

other(method=None, record_id=None, representation=None)

  • returns the URL of a request with another method and record ID, but for the same resource

target()

  • returns the target table of the current request as tuple of (prefix, name, table, tablename)

export_xml(permit=None, audit=None, template=None, filterby=None, pretty_print=False)

  • exports the requested resources as XML

export_json(permit=None, audit=None, template=None, filterby=None, pretty_print=False)

  • exports the requested resources as JSON

import_xml(tree, permit=None, audit=None, onvalidation=None, onaccept=None)

  • import the requested resources from the given ElementTree

options_xml(pretty_print=False)

  • exports the options of a field (or all fields) in the resource as XML

options_json(pretty_print=False)

  • exports the options of a field (or all fields) in the resource as JSON

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