Re: [mapserver-users] Setting up a JSONP service

Lars Fricke Wed, 14 Jan 2015 08:08:49 -0800

Hi Steve,

I really appreciate that you took this effort! In the meantime (after Iwrote my question to you), Andreas has come up with a more directsolution and since we will have quite some traffic on the server Iexpect we will need every bit of performance. So I guess we will not usetemplates after all. Anyway, it's great how people on this list respondwith different good solutions and suggestions! Thank you!


Best

Lars

Am 14.01.2015 um 00:41 schrieb Lime, Steve D (MNIT):

Hi Lars: Most of what you need was in my last reply. Those are snippets from a 
working configuration. Here's a simple JSON template for a raster query that 
creates an array of xyz objects:

// MapServer Template
{'result':{
   'points':[
[resultset layer="elev_dem30ra3"]
   [feature trimlast=","]{x:[x], y:[y], z:[value_0]},[/feature]
[/resultset]
   ]
}}

You could turn this into JSONP and not use the include strategy (I wanted both JSON and 
JSONP) simply by wrapping the object in callback (callback is a value passed through 
MapServer, e.g. &mode=query&callback=foo):

// MapServer Template (jsonp.js)
[callback]({'result':{
   'points':[
[resultset layer="elev_dem30ra3"]
   [feature trimlast=","]{x:[x], y:[y], z:[value_0]},[/feature]
[/resultset]
   ]
}})

and here's the corresponding OUTPUTFORMAT block:

OUTPUTFORMAT
   NAME 'JSONP'
   DRIVER 'TEMPLATE'
   MIMETYPE 'application/json;'
   FORMATOPTION 'FILE=templates/jsonp.js'
   FORMATOPTION 'ATTACHMENT=service.json'
END

Regarding speed, templates are going to be a bit slower since there are 
generally two passes through the data, once to identify the candidate records 
and a second for presentation. Also the template assembly is done in memory so 
there are limits on how large of datasets you can practically work with. How 
big a deal this is depends on your situation. It's not perfect but in general 
I've had great luck with this approach.

Steve

-----Original Message-----
From: mapserver-users-boun...@lists.osgeo.org 
[mailto:mapserver-users-boun...@lists.osgeo.org] On Behalf Of Lars Fricke
Sent: Friday, January 09, 2015 4:24 AM
To: mapserver-users@lists.osgeo.org
Subject: Re: [mapserver-users] Setting up a JSONP service

Hello,

first of all: Thank you for your support!
Sorry for the late reply but I unfortunately was ill.

@ Steve:
I read about templating but also read that it is slower?
I do not have a lot of experience in writing templates. Would you mind sharing 
a JSONP template?

@ Even: Thank you for your thoughts. Who would implement that change though? 
I'm afraid I can't.

@ Jeff: I followed those links but I only found threads referring to GeoServer 
or that were not related to my question. The GDAL page I did study and that's 
how I managed to set up the GeoJSON service but thats not the same 
unfortunately as it conflicts with the same origin policy.

Best

Lars

Am 30.12.2014 um 16:24 schrieb Lime, Steve D (MNIT):

You can also use MapServer templates to accomplish this. It's a little more 
work since you have to write the template but it's quite flexible then. Usually 
I write the template to produce JSON and then use a simple wrapper template to 
produce JSONP. For example, jsonp.js looks like (callback is passed in):

// MapServer Template
[callback](
    [include src="templates/json.js"]
)

Output formats look like:

    OUTPUTFORMAT
      NAME 'JSON'
      DRIVER 'TEMPLATE'
      MIMETYPE 'application/json;'
      FORMATOPTION 'FILE=templates/json.js'
      FORMATOPTION 'ATTACHMENT=service.json'
    END

    OUTPUTFORMAT
      NAME 'JSONP'
      DRIVER 'TEMPLATE'
      MIMETYPE 'application/json;'
      FORMATOPTION 'FILE=templates/jsonp.js'
      FORMATOPTION 'ATTACHMENT=service.json'
    END

Steve

-----Original Message-----
From:mapserver-users-boun...@lists.osgeo.org
[mailto:mapserver-users-boun...@lists.osgeo.org] On Behalf Of Lars
Fricke
Sent: Monday, December 29, 2014 5:34 AM
To:mapserver-users@lists.osgeo.org
Subject: [mapserver-users] Setting up a JSONP service

Dear List,

I have a WFS service running under MapServer that I would like to operate as JSONP 
service. I managed to set GEOJSON as output format but I get "Cross-Origin-Request 
Blocked" if I try to call it with a Javascript client (using Leaflet L.layerJSON.
The question is: Is it possible to set up a JSONP service from Mapserver and if 
yes, how? My current mapfile looks like this (relevant parts):

"
# in WEB - METADATA
"wfs_getfeature_formatlist" "geojson,csv,ogrgml"

OUTPUTFORMAT
      NAME "geojson"
      DRIVER "OGR/GEOJSON"
      MIMETYPE "application/json; subtype=geojson; charset=utf-8"
      FORMATOPTION "STORAGE=stream"
      FORMATOPTION "FORM=SIMPLE"
      FORMATOPTION "LCO:COORDINATE_PRECISION=5"
     END
"
If this would already be a correct JSONP service, I have to look on the Leaflet 
side for the error...
Thanks for your help.

Cheers

Lars
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Re: [mapserver-users] Setting up a JSONP service

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