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 registered into 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 XRequest 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_RESTlike_controller.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 XRequest, 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 (XRequest) and attr.

XRequest

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

Attributes of the XRequest

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

Controller Attributes

rc	the resource controller object (S3XRC)
request	the original web2py request (Storage)
session	the current session (Storage)

Request Attributes

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

Primary Resource Attributes

prefix	the prefix (=module name) of the requested resource (string)
name	the name of the requested resource, without prefix (string)
tablename	the name of the primary table (string)
table	the primary table (Table)
id	the ID of the primary record (int)
record	the primary record (Row)

Component Resource Attributes

component	the requested component, if any (ObjectComponent)
pkey	the primary key of the Resource/Component join (string)
fkey	the foreign key of the Resource/Component join (string)
component_name	the name of the component without prefix (string)
component_id	the ID of the component record as of the request, if any (int)
multiple	Flag indicating that multiple component records are allowed (boolean)

Error Indicators

error	the last error message (string)
invalid	Flag indicating this request as invalid (boolean)
badmethod	Flag indicating a bad method error (boolean)
badrecord	Flag indicating a invalid record ID error (boolean)
badrequest	Flag 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 XRequest

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