4.6.2 FieldStorage Examples

The following examples demonstrate how to use the file_callback parameter of the FieldStorage constructor to control file object creation. The Storage classes created in both examples derive from FileType, thereby providing extended file functionality.

These examples are provided for demonstration purposes only. The issue of temporary file location and security must be considered when providing such overrides with mod_python in production use.

Simple file control using class constructor

This example uses the FieldStorage class constructor to create the file object, allowing simple control. It is not advisable to add class variables to this if serving multiple sites from apache. In that case use the factory method instead.

class Storage(file):

    def __init__(self, advisory_filename):
        self.advisory_filename = advisory_filename
        self.delete_on_close = True
        self.already_deleted = False
        self.real_filename = '/someTempDir/thingy-unique-thingy'
        super(Storage, self).__init__(self.real_filename, 'w+b')

    def close(self):
        if self.already_deleted:
            return
        super(Storage, self).close()
        if self.delete_on_close:
            self.already_deleted = True
            os.remove(self.real_filename)

request_data = util.FieldStorage(request, keep_blank_values=True, file_callback=Storage)

Advanced file control using object factory

Using a object factory can provide greater control over the constructor parameters.

import os

class Storage(file):

    def __init__(self, directory, advisory_filename):
        self.advisory_filename = advisory_filename
        self.delete_on_close = True
        self.already_deleted = False
        self.real_filename = directory + '/thingy-unique-thingy'
        super(Storage, self).__init__(self.real_filename, 'w+b')

    def close(self):
        if self.already_deleted:
            return
        super(Storage, self).close()
        if self.delete_on_close:
            self.already_deleted = True
            os.remove(self.real_filename)

class StorageFactory:

    def __init__(self, directory):
        self.dir = directory

    def create(self, advisory_filename):
        return Storage(self.dir, advisory_filename)

file_factory = StorageFactory(someDirectory)
[...sometime later...]
request_data = util.FieldStorage(request, keep_blank_values=True,
                                file_callback=file_factory.create)