One thing to be aware of, in the code of an application, is which part of a path refers to the location of the application in a server environment, and which refers to some resource within the application itself. Consider this path:
/folder/application/resource/operation
Let us say
that the application
was deployed in a Zope server
instance
inside
folder
and with the name application
.
We may
then
say that the path to the application is this:
/folder/application
Meanwhile, the path within the application is just this:
/resource/operation
In WebStack, we refer to this latter case - the path within the application - as the "path info".
On transaction objects, the following methods exist to inspect paths to resources within applications.
get_path_info
/
character at the very least.encoding
parameter may be
used to assist the process of converting the path to a Unicode object -
see "Character Encodings"
for more information.get_virtual_path_info
set_virtual_path_info
method. The path should either contain a leading /
character optionally followed by other characters, or an empty string.encoding
parameter may be
used to assist the process of converting the path to a Unicode object -
see "Character Encodings"
for more information.get_processed_virtual_path_info
encoding
parameter may be
used to assist the process of converting the path to a Unicode object -
see "Character Encodings"
for more information.Given that the path may change depending on where an application is deployed in a server environment, it may not be very easy to use when determining which resources are being requested or accessed within your application. Conversely, given that the "path info" does not mention the full path to where the resources are, it may be difficult to use that to provide references or links to those resources. Here is a summary of how you might use the different path values:
Type of information | Possible uses |
---|---|
Path | Building links to resources within an application. |
Path without path info | Finding the location of the application in a server environment. (This is the path with the "path info" subtracted from the end.) |
Path info | Determining which resources are being accessed within an application. |
Virtual path info | This is an application-defined version of "path info" and is discussed below. |
Although WebStack sets the "path info" so that applications know which part of themselves are being accessed, you may decide that upon processing the request, these different parts of your application should be presented with different path information. For example, in a hierarchical structure of resources, each resource might use the first part of the "path info" as an input to some kind of processing, but then have the need to remove the part they used, passing on a modified path to the other resources. For such approaches, the "virtual path info" may be used instead, since it permits modification within an application.
So starting with a virtual path like this (which would be the same as the "path info")...
/company/department/employee
...a
resource might extract company
from
the start
of the path as follows:
# Inside a respond method...
path = trans.get_virtual_path_info() # get the virtual path
parts = path.split("/") # split the path into components - the first will be empty
Then, having processed the first non-empty part (remembering that the first part will be an empty string)...
if len(parts) > 1: # check to see how deep we are in the path
process_something(parts[1]) # process the first non-empty part
...it
will reconstruct the path, removing the processed part (but
remembering to preserve a leading /
character)...
trans.set_virtual_path_info("/" + "/".join(parts[2:]))
...and
hand over control to another resource which would do the same
thing with the first of the other path components (department
and employee
), and so on.
The compelling thing about this strategy is the way that each resource would only need to take the "virtual path info" into consideration, and that each resource would believe that it is running independently from any "parent" resource. Moreover, such resources could be deployed independently and still operate in the same way without being "hardcoded" into assuming that they always reside at a particular level in a resource hierarchy.
On transaction objects, the following method exists to set virtual paths within applications.
set_virtual_path_info
get_virtual_path_info
method. The path should either contain a leading /
character optionally followed by other characters, or an empty string.The following illustration hopefully provides a more memorable way of representing the structure of paths:
URL | |||||
---|---|---|---|---|---|
Protocol, host, port | Path | ||||
Path without query | Query | ||||
Path without path info | Path info | ||||
Processed virtual path info | Virtual path info | ||||
http://www.python.org | /folder/application | /resource | /operation | ? | a=1&b=2 |