HTTP Plugin

Overview

This plugin provides a high-level interface for accessing World-Wide Web resources. The name is somewhat misleading because the plugin can access http, ftp, and gopher URLs. To use the plugin, a KP must first lookup a connector for an HTTPAPI.Factory object and use it to create a new HTTPAPI.Requester.

Objects

This module defines the following object types:

Factory

The Factory generates new Requester objects. The plugin registers this object with the name 'http'.

Requester

The Requester loads Web resources.

Methods of Factory object

Instances of the Factory object have the following method:

Factory() : HTTPAPI.Requester

Returns a new Requester object that can be used to load URLs. A FactoryFailed exception may be raised if a system error occurs.

Methods of Requester object

Instances of the Requester object have the following methods:

Get(url : string) : FileAPI.File

Requests the resource addressed by url. Returns the resource as a file-like objects or raises a FileAPI.FileIOError exception if the request resource could not be loaded.

GetWithInfo(url : string) : list of list of string, FileAPI.File

Requests the resource address by url. Returns the headers from the HTTP response and the resource body. The headers are represented as a list of key-value pairs, where the pairs are lists with two elements. (For ftp and gopher responses, the list of headers will be empty.)

In an error occurs, a FileAPI.FileIOError will be raised.

ASYNCHRONOUS Close()

Destroys the Requester object. If you don't call this method, the system will not be able to reclaim the resources used by the Requester.

Exceptions

This module defines the following exceptions:

FactoryFailed

The Factory could not create a new HTTP Requester because of a system error.

Limitations

• IF the KP fails to Close() the Requester instance it has created, it will cause the child process to hang around forever, since ILU doesn't do garbage collection.

• HTTP error codes returned by the server are translated into FileAPI.FileIOError exceptions. The problem with this is that the KP has to parse the error message string to get the numeric error code. Moreover, the headers that came along with the error code are lost. All this makes using the GetWithInfo interface less pleasant than using urllib.urlopen() directly.

• The KP may be denied access by the plugin for a particular URL based on the HTTP Plugin's access.conf permissions database.