Changes between Version 7 and Version 8 of ZooWorkshop/FOSS4GJapan/CreatingOGRBasedWebServices


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Timestamp:
Oct 15, 2010, 5:52:16 PM (9 years ago)
Author:
djay
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  • ZooWorkshop/FOSS4GJapan/CreatingOGRBasedWebServices

    v7 v8  
    150150=== Boundary ===
    151151
    152 ==== C Version ====
     152=== C Version ===
    153153
    154154As explained before, ZOO Kernel will pass the parameters to your Service function in a specific datatype called maps. In order to code your Service in C language, you also need to learn how to access this datatype in read/write mode.
     
    428428Your ZOO Services Provider is now ready to use from an Execute request passed to ZOO Kernel.
    429429
    430 ==== Python Version ====
     430=== Python Version ===
     431
     432For those using Python to implement their ZOO Services Provider, the full code to copy in ogr_ws_service_provider.py in cgi-env directory is shown bellow. Indeed, as Python is an interpreted language, you do not have to compile anything before deploying your service which makes the deployement step much easier :
     433
     434{{{
     435#!python
     436import osgeo.ogr
     437import libxml2
     438
     439def createGeometryFromWFS(my_wfs_response):
     440    doc=libxml2.parseMemory(my_wfs_response,len(my_wfs_response))
     441    ctxt = doc.xpathNewContext()
     442    res=ctxt.xpathEval("/*/*/*/*/*[local-name()='Polygon' or local- name()='MultiPolygon']")
     443    for node in res:
     444        geometry_as_string=node.serialize()
     445        geometry=osgeo.ogr.CreateGeometryFromGML(geometry_as_string)
     446        return geometry
     447    return geometry
     448
     449def Boundary(conf,inputs,outputs):
     450    if inputs["InputPolygon"]["mimeType"]=="application/json":
     451        geometry=osgeo.ogr.CreateGeometryFromJson(inputs["InputPolygon"]["value"])
     452    else:
     453        geometry=createGeometryFromWFS(inputs["InputPolygon"]["value"])
     454    rgeom=geometry.GetBoundary()
     455    if outputs["Result"]["mimeType"]=="application/json":
     456        outputs["Result"]["value"]=rgeom.ExportToJson()
     457        outputs["Result"]["mimeType"]="text/plain"
     458    else:
     459        outputs["Result"]["value"]=rgeom.ExportToGML()
     460    geometry.Destroy()
     461    rgeom.Destroy()
     462    return 3
     463}}}
     464
     465We do not dicuss the functions body here as we already gave all the details before and the code was volontary made in a similar way.
     466
     467As done before, you only have to copy the cgi-env files into your cgi-bin directory :
     468
     469{{{
     470#!sh
     471sudo cp ./cgi-env/* /usr/lib/cgi-bin
     472}}}
     473
     474A simple Makefile containing the install section can be written as the following :
     475
     476{{{
     477install:
     478        sudo cp ./cgi-env/* /usr/lib/cgi-bin/
     479}}}
     480
     481Finally, simply run make install from the ZOO Services Provider main directory, in order to deploy your ZOO Service Provider.
     482
     483=== Testing the Service using Execute Request ===
     484
     485==== The simple and unreadable way ====
     486
     487Everybody should now get his own copy of the OGR Boundary Service stored as a ZOO Services Provider called ogr_ws_service_provider and deployed in the ZOO Kernel tree, so the following Execute request can be used to test the Service :
     488
     489[http://localhost/cgi-bin/zoo_loader.cgi?request=Execute&service=WPS&version=1.0.0&Identifier=Boundary&DataInputs=InputPolygon=Reference@xlink:href= http%3A%2F%2Flocalhost%3A8082%2Fgeoserver%2Fows%3FSERVICE%3DWFS%26REQUEST%3DGetFeature%26VERSION%3D1.0.0%26typename%3Dtopp%3Astates%26SRS%3DEPSG%3A4326%26FeatureID%3Dstates.15]
     490
     491As you can see in the url above, we use an URLEncoded WFS request to the Geoserver WFS server available on OSGeoLive as a xlink:href key in the DataInputs KVP value, and set the InputPolygon value to Reference. The corresponding non encoded WFS request is as follow :
     492
     493[http://localhost:8082/geoserver/ows/?SERVICE=WFS&REQUEST=GetFeature&VERSION=1.0.0&typename=topp:states&SRS=EPSG:4326&FeatureID=state s.15]
     494
     495Please note that you can add lineage=true to the previous request if you need to get information about the input values used to run your Service. Furthermore, you may need to store theExecuteResponse document of your ZOO Service to re-use it later. In this case you must addstoreExecuteResponse=true to the previous request. Note that is an important thing as the behavior of ZOO Kernel is not exactly the same than when running without this parameter settled to true. Indeed, in such a request, ZOO Kernel will give you an ExecuteResponse document which will contain the attribute statusLocation, which inform the client where the ongoing status or the final ExecuteResponse will be located.
     496
     497Here is an example of what the ExecuteResponse using storeExecuteResponse=true in the request would look like :
     498
     499Then, according to the statusLocation, you should get the ExecuteResponse as you get before using the previous request. Note that can be really useful to provide some caching system for a client application.
     500
     501You didn't specify any ResponseForm in the previous request, it is not requested and should return a ResponseDocument per default using the application/json mimeType as you defined in you zcfg file. Nevertheless, you can tell ZOO Kernel what kind of data you want to get in result of your query adding the attribute mimeType=text/xml to your ResponseDocument parameter. Adding this parameter to the previous request will give us the result as its GML representation :
     502
     503[http://localhost/cgi-bin/zoo_loader.cgi?request=Execute&service=WPS&version=1.0.0&Identifier=Boundary&DataInputs=InputPolygon=Reference@xlink:href= http%3A%2F%2Flocalhost%3A8082%2Fgeoserver%2Fows%3FSERVICE%3DWFS%26REQUEST%3DGetFeature%26VERSION%3D1.0.0%26typename%3Dtopp%3Astates%26SRS%3DEPSG%3A4326%26FeatureID %3Dstates.15&ResponseDocument=Result@mimeType=text/xml]
     504
     505As defined by the WPS specifications, you can also ask for a RawDataOutput to get only the data without the full ResponseDocument. To do that, you only have to replace the ResponseDocument of your request by RawDataOutput, like in the following request :
     506
     507[http://localhost/cgi-bin/zoo_loader.cgi?request=Execute&service=WPS&version=1.0.0&Identifier=Boundary&DataInputs=InputPolygon=Reference@xlink:href= http%3A%2F%2Flocalhost%3A8082%2Fgeoserver%2Fows%3FSERVICE%3DWFS%26REQUEST%3DGetFeature%26VERSION%3D1.0.0%26typename%3Dtopp%3Astates%26SRS%3DEPSG%3A4326%26FeatureID %3Dstates.15&RawDataOutput=Result@mimeType=application/json]
     508
     509Finally, please note that we go back to the default mimeType to directly obtain the JSON string as we will use this kind of request to develop our client application in the next section of this workshop.
     510
     511==== Simplification and readability of request ====
     512
     513As you can see in the simple example we used since the begining of this workshop, it is sometimes hard to write the Execute requests using the GET method as it makes really long and complexe URLs. In the next requests examples, we will thus use the POST XML requests. First , here is the XML request corresponding to the previous Execute we used :
     514
     515{{{
     516#!xml
     517<wps:Execute service="WPS" version="1.0.0" xmlns:wps="http://www.opengis.net/wps/1.0.0" xmlns:ows="http://www.opengis.net/ows/1.1" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.opengis.net/wps/1.0.0 ../wpsExecute_request.xsd">
     518 <ows:Identifier>Boundary</ows:Identifier>
     519 <wps:DataInputs>
     520  <wps:Input>
     521   <ows:Identifier>InputPolygon</ows:Identifier>
     522   <ows:Title>Playground area</ows:Title>
     523   <wps:Reference xlink:href="http://localhost:8082/geoserver/ows/?SERVICE=WFS&amp;REQUEST=GetFeature&amp;VERSION=1.0.0&amp;typename=topp:states&amp;SRS=EPSG:43 26&amp;FeatureID=states.15"/>
     524  </wps:Input>
     525 </wps:DataInputs>
     526 <wps:ResponseForm>
     527  <wps:ResponseDocument>
     528   <wps:Output>
     529    <ows:Identifier>Result</ows:Identifier>
     530    <ows:Title>Area serviced by playground.</ows:Title>
     531    <ows:Abstract>Area within which most users of this playground will live.</ows:Abstract>
     532   </wps:Output>
     533  </wps:ResponseDocument>
     534 </wps:ResponseForm>
     535</wps:Execute>
     536}}}
     537
     538In order to let you easily run the XML requests, a simple HTML form called test_services.html is available in your /var/www directory. You can access it using the following link : http://localhost/test_services.html.
     539
     540Please open this page in your browser, simply fill the XML request content into the textarea field and click the « run using XML Request » submit button. You will get exactly the same result as when running your Service using the GET request. The screenshot above show the HTML form including the request and the ExecuteResponse document displayed in the iframe at the bottom of the page :
     541
     542The xlink:href value is used in the simplest way to deal with such data input. Obviously, you can also use a full JSON string of the geometry, as shown in the following XML Request example :
     543
     544{{{
     545#!xml
     546<wps:Execute service="WPS" version="1.0.0" xmlns:wps="http://www.opengis.net/wps/1.0.0" xmlns:ows="http://www.opengis.net/ows/1.1" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.opengis.net/wps/1.0.0 ../wpsExecute_request.xsda">
     547 <ows:Identifier>Boundary</ows:Identifier>
     548 <wps:DataInputs>
     549  <wps:Input>
     550   <ows:Identifier>InputPolygon</ows:Identifier>
     551   <wps:Data>
     552    <wps:ComplexData mimeType="application/json">
     553{ "type": "MultiPolygon", "coordinates": [ [ [ [ -105.998360, 31.393818 ], [ -106.212753, 31.478128 ], [ -106.383041, 31.733763 ], [ -106.538971, 31.786198 ], [ -106.614441, 31.817728 ], [ -105.769730, 31.170780 ], [ -105.998360, 31.393818 ] ] ], [ [ [ -94.913429, 29.257572 ], [ -94.767380, 29.342451 ], [ -94.748405, 29.319490 ], [ -95.105415, 29.096958 ], [ -94.913429, 29.257572 ] ] ] ] }
     554    </wps:ComplexData>
     555   </wps:Data>
     556  </wps:Input>
     557 </wps:DataInputs>
     558 <wps:ResponseForm>
     559  <wps:ResponseDocument>
     560   <wps:Output>
     561    <ows:Identifier>Result</ows:Identifier>
     562    <ows:Title>Area serviced by playground.</ows:Title>
     563    <ows:Abstract>Area within which most users of this playground will live.</ows:Abstract>
     564   </wps:Output>
     565  </wps:ResponseDocument>
     566 </wps:ResponseForm>
     567</wps:Execute>
     568}}}
     569
     570If everything went well, you should get the Boundary of the JSON geometry passed as argument, and so be sure that your Service support both GML and JSON as input data. Note that in the previous request, we added a mimeType attribute to the ComplexData node to specify that the input data is not in the default text/xml mimeType but passed as an application/json string directly. It is similar to add @mimeType=application/json as we discussed before.
     571
     572== Creating Services for other functions (ConvexHull and Centroid) ==

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