Python Scripting Hooks¶

app¶

The app hook provides a way to add scripts that are invoked via HTTP. Scripts are provided with a WSGI environment for execution. A simple hello world example looks like this:

def app(environ, start_response):
   start_response('200 OK', [('Content-type','text/plain')])
   return 'Hello world!'

The script must define a function named app that takes an environ which is a dict instance that contains information about the current request, and the executing environment. The start_response method starts the response and takes a status code and a set of response headers.

The app method returns an iterator that generates the response content, or just a single string representing the entire body.

For more information about WSGI go to http://wsgi.org.

datastore¶

TODO

filter¶

The filter hook provides filter function implementations to be used in an OGC filter. These filters appear in WFS queries, and in SLD styling rules.

A simple filter function looks like this:

from geoserver.filter import function
from geoscript.geom import Polygon

@function
def areaGreaterThan(feature, area):
  return feature.geom.area > area

The above function returns true or false depending on if the area of a feature is greater than a certain threshold.

format¶

The format hook provides output format implementations for various OWS service operations. Examples include PNG for WMS GetMap, GeoJSON and GML for WFS GetFeature, HTML and plain text for WMS GetFeatureInfo.

Currently formats fall into two categories. The first are formats that can encode vector data (features). A simple example looks like:

from geoserver.format import vector_format

@vector_format('property', 'text/plain')
def write(data, out):
 for feature in data.features:
   out.write("%s=%s\n" % (f.id, '|'.join([str(val) for val in f.values()])))

The above function encodes a set of features as a java property file. Given the following feature set:

Feature(id="fid.0", geometry="POINT(0 0)", name="zero")
Feature(id="fid.1", geometry="POINT(1 1)", name="one")
Feature(id="fid.2", geometry="POINT(1 1)", name="two")

The above function would output:

fid.0=POINT(0 0)|one
fid.1=POINT(1 1)|two
fid.2=POINT(2 2)|three

Vector formats can be invoked by the following service operations:

• WFS GetFeature (?outputFormat=property)
• WMS GetMap (?format=property)
• WMS GetFeatureInfo (?info_format=property)

A vector format is a python function that is decorated by the vector_format decorator. The decorator accepts two arguments. The first is the name of the output format. This is the identifier that clients use to request the format. The second parameter is the mime type that describes the type of content the format creates.

The second type of output format is one that encodes a complete map. This format can only be used with the WMS GetMap operation.

TODO: example

process¶

The process hook provides process implementations that are invoked by the GeoServer WPS. A simple example looks like:

from geoserver import process
from geoscript.geom import Geometry

@process('Buffer', 'Buffer a geometry', args=[('geom', Geometry)],
         result=('The buffered result', Geometry))
def buffer(geom):
   return geom.buffer(10)

A process is a function that is decorated by the process decorator. The decorator takes the following arguments:

The args parameter is a list of tuples describing the input arguments of the process. Each tuple can contain up to three values. The first value is the name of the parameter and is mandatory. The second value is the type of the parameter and is optional. The third value is a description of the parameter and is optional.

The result parameter describes the result of the process and is a tuple containing up to two values. This parameter is optional. The first value is the type of the result and the second value is a description of the result.