NAME
Geo::OGC::Service - Perl extension for geospatial web services
SYNOPSIS
In a service.psgi file write something like this
use strict;
use warnings;
use Plack::Builder;
use Geo::OGC::Service;
use Geo::OGC::Service::XXX;
my $server = Geo::OGC::Service->new({
config => '/var/www/etc/test.conf',
services => {
XXX => 'Geo::OGC::Service::XXX',
}
});
builder {
mount "/XXX" => $server->to_app;
mount "/" => $default_app;
};The bones of a service class are
package Geo::OGC::Service::XXX;
sub process_request {
my ($self, $responder) = @_;
my $writer = $responder->([200, [ 'Content-Type' => 'text/plain',
'Content-Encoding' => 'UTF-8' ]]);
$writer->write("I'm ok!");
$writer->close;
}Geo::OGC::Service::WFS exists in the CPAN and Geo::OGC::Service::WMTS will be there real soon now.
DESCRIPTION
This module provides a to_app method for booting a web service. Geo::OGC::Service is a subclass of Plack::Component.
SERVICE CONFIGURATION
Setting up a PSGI service consists typically of three things:
1) write a service.psgi file (see above) and put it somewhere like
/var/www/service/service.psgi 2) Set up starman service and add to its init-file line something like
exec starman --daemonize --error-log /var/log/starman/log --l localhost:5000 /var/www/service/service.psgi3) Add a proxy service to your apache configuration
<Location /Service>
ProxyPass http://localhost:5000
ProxyPassReverse http://localhost:5000
</Location>Setting up a geospatial web service through this module requires a configuration file, for example
/var/www/etc/service.conf
(make sure this file is not served by apache)
The configuration must be in JSON format. I.e., something like
{
Common: {
"CORS": "*",
"Content-Type": "text/xml; charset=utf-8",
"version": "1.1.0",
"TARGET_NAMESPACE": "http://ogr.maptools.org/"
},
WFS: {
...WFS configuration...
}
}The keys and structure of this file depend on the type of the service(s) you are setting up. "CORS" is the only one that is recognized by this module. "CORS" is either a string denoting the allowed origin or a hash of "Allow-Origin", "Allow-Methods", "Allow-Headers", and "Max-Age".
EXPORT
None by default.
METHODS
new
This creates a new Geo::OGC::Service app. You need to call it in the psgi file as a class method with a named parameter hash reference. The parameters are
config, servicesconfig is required and it is a path to a file or a reference to an anonymous hash containing the configuration for the services.
services is a reference to a hash of service names associated with names of classes, which will process service requests. The key of the hash is the requested service.
call
This method is called internally by the method to_app of Plack::Component. The method fails unless this module is running in a psgi.streaming environment. Otherwise, it returns a subroutine, which calls the respond method.
respond
This method is called for each request from the Internet. The call is responded during the execution of the subroutine.
In the default case this method constructs a new service object using the method 'service' and calls its process_request method with PSGI style $responder object as a parameter.
This subroutine may fail while interpreting the request, or while processing the request.
service
This method does a preliminary interpretation of the request and converts it into a service object, which is returned. The contents of the configuration are cloned into the service object.
The returned service object contains
config => a clone of the configuration for this type of service
env => the PSGI environmentand may contain
posted => XML::LibXML DOM document element of the posted data
filter => XML::LibXML DOM document element of the filter
parameters => hash of rquest parameters obtained from Plack::RequestNote: all keys in request parameters are converted to lower case in parameters.
This subroutine may fail due to a request for an unknown service. The error is reported as an XML message using OGC conventions.
error($responder, $msg)
Stream an error report as an XML message of type
<?xml version="1.0" encoding="UTF-8"?>
<ExceptionReport>
<Exception exceptionCode="$msg->{exceptionCode}" locator="$msg->{locator}">
<ExceptionText>$msg->{ExceptionText}<ExceptionText>
<Exception>
</ExceptionReport>Geo::OGC::Service::Common
A base type for all OGC services.
SYNOPSIS
$service->DescribeService($writer);
$service->Operation($writer, $operation, $protocols, $parameters);DESCRIPTION
The class contains methods for common tasks for all services.
METHODS
CORS
Return the CORS headers as a list according to the configuration. CORS may be in the configuration as a scalar or as a hash. A scalar value is taken as a value for Access-Control-Allow-Origin. A hash may have the following keys. (Note the missing prefix Access-Control-.)
key default value
----------------- ----------------------------------
Allow-Origin
Allow-Credentials
Expose-Headers
Max-Age 60*60*24
Allow-Methods GET,POST
Allow-Headers origin,x-requested-with,content-typeDescribeService($writer)
Create ows:ServiceIdentification and ows:ServiceProvider elements.
Operation($writer, $operation, $protocols, $parameters)
Create ows:Operation element and its ows:DCP and ows:Parameter sub elements.
Geo::OGC::Service::XMLWriter
A helper class for writing XML.
SYNOPSIS
my $writer = Geo::OGC::Service::XMLWriter::Caching->new();
$writer->open_element(
'wfs:WFS_Capabilities',
{ 'xmlns:gml' => "http://www.opengis.net/gml" });
$writer->element('ows:ServiceProvider',
[['ows:ProviderName'],
['ows:ProviderSite', {'xlink:type'=>"simple", 'xlink:href'=>""}],
['ows:ServiceContact']]);
$writer->close_element;
$writer->stream($responder);or
my $writer = Geo::OGC::Service::XMLWriter::Streaming->new($responder);
$writer->prolog;
$writer->open_element('MyXML');
while (a long time) {
$writer->element('MyElement');
}
$writer->close_element;
# $writer is closed when it goes out of scopeDESCRIPTION
The classes Geo::OGC::Service::XMLWriter (abstract), Geo::OGC::Service::XMLWriter::Streaming (concrete), and Geo::OGC::Service::XMLWriter::Caching (concrete) are provided as a convenience for writing XML to the client.
The element method has the syntax
$writer->element($tag[, $attributes][, $content])or
$writer->element($element)where $element is a reference to an array [$tag[, $attributes][, $content]].
$attributes is a reference to a hash
$content is nothing, undef, '/>', plain content (string), an element (as above), a list of elements, or a reference to a list of elements. If there is no $content or $content is undef, a self-closing tag is written. If $content is '/>' a closing tag is written.
Setting $tag to 0 or 1, allows writing plain content.
If $attribute{$key} is undefined the attribute is not written at all.
Geo::OGC::Service::XMLWriter::Streaming
A helper class for writing XML into a stream.
SYNOPSIS
my $w = Geo::OGC::Service::XMLWriter::Streaming($responder, $headers, $declaration);Using $w as XMLWriter sets writer, which is obtained from $responder, to write XML. The writer is closed when $w is destroyed.
$headers and $declaration are optional. The defaults are 'Content-Type' => 'text/xml; charset=utf-8' and '<?xml version="1.0" encoding="UTF-8"?>'.
Geo::OGC::Service::XMLWriter::Caching
A helper class for writing XML into a cache.
SYNOPSIS
my $w = Geo::OGC::Service::XMLWriter::Caching($headers, $declaration);
$w->stream($responder);Using $w to produce XML caches the XML. The cached XML can be written by a writer obtained from a $responder.
$headers and $declaration are optional. The defaults are as in Geo::OGC::Service::XMLWriter::Streaming.
SEE ALSO
Discuss this module on the Geo-perl email list.
https://list.hut.fi/mailman/listinfo/geo-perl
For PSGI/Plack see
REPOSITORY
https://github.com/ajolma/Geo-OGC-Service
AUTHOR
Ari Jolma, <ari.jolma at gmail.com>
COPYRIGHT AND LICENSE
Copyright (C) 2015 by Ari Jolma
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.22.0 or, at your option, any later version of Perl 5 you may have available.