Despite our constant efforts, information beyond this line may not be updated for QGIS 3. Refer to https://qgis.org/pyqgis/master for the python API documentation or, give a hand to update the chapters you know about. Thanks.

Python plugins can also run on QGIS Server (see OGCデータサーバーとしてのQGIS):

  • By using the server interface (QgsServerInterface) a Python plugin running on the server can alter the behavior of existing core services (WMS, WFS etc.).

  • With the server filter interface (QgsServerFilter) you can change the input parameters, change the generated output or even provide new services.

  • With the access control interface (QgsAccessControlFilter) you can apply some access restriction per requests.


Server python plugins are loaded once when the FCGI application starts. They register one or more QgsServerFilter (from this point, you might find useful a quick look to the server plugins API docs). Each filter should implement at least one of three callbacks:

All filters have access to the request/response object (QgsRequestHandler) and can manipulate all its properties (input/output) and raise exceptions (while in a quite particular way as we’ll see below).


  • 着信要求を取得
    • GET/POST/SOAPリクエストハンドラを作成

    • pass request to an instance of QgsServerInterface

    • call plugins requestReady filters

    • 応答がない場合
      • サービスがWMS/WFS/WCSであれば
        • WMS/WFS/WCSサーバーを作成
          • call server’s executeRequest and possibly call sendResponse plugin filters when streaming output or store the byte stream output and content type in the request handler

      • call plugins responseComplete filters

    • call plugins sendResponse filters

    • 要求ハンドラの出力応答




  • 認証/認可

  • リダイレクト

  • 特定のパラメーター(例えば、型名)を追加/除去

  • 例外を発生させる

SERVICE パラメーターを変更することでコアサービスを完全に置き換え、それによりコアサービスを完全にバイパスすることさえできるかもしれません(とはいえ、これはあまり意味がないということ)。


This is called whenever output is sent to FCGI stdout (and from there, to the client), this is normally done after core services have finished their process and after responseComplete hook was called, but in a few cases XML can become so huge that a streaming XML implementation was needed (WFS GetFeature is one of them), in this case, sendResponse is called multiple times before the response is complete (and before responseComplete is called). The obvious consequence is that sendResponse is normally called once but might be exceptionally called multiple times and in that case (and only in that case) it is also called before responseComplete.

sendResponse is the best place for direct manipulation of core service’s output and while responseComplete is typically also an option, sendResponse is the only viable option in case of streaming services.


This is called once when core services (if hit) finish their process and the request is ready to be sent to the client. As discussed above, this is normally called before sendResponse except for streaming services (or other plugin filters) that might have called sendResponse earlier.

responseComplete is the ideal place to provide new services implementation (WPS or custom services) and to perform direct manipulation of the output coming from core services (for example to add a watermark upon a WMS image).


Some work has still to be done on this topic: the current implementation can distinguish between handled and unhandled exceptions by setting a QgsRequestHandler property to an instance of QgsMapServiceException, this way the main C++ code can catch handled python exceptions and ignore unhandled exceptions (or better: log them).

このアプローチは、基本的に動作しますが、それは非常に「パイソン的」ではありません:より良いアプローチは、Pythonコードから例外を発生し、それらがそこで処理されるためにC ++ループに湧き上がるのを見ることでしょう。


A server plugin is a standard QGIS Python plugin as described in Pythonプラグインを開発する, that just provides an additional (or alternative) interface: a typical QGIS desktop plugin has access to QGIS application through the QgisInterface instance, a server plugin has also access to a QgsServerInterface.

プラグインがサーバー・インターフェイスを持つことをQGISサーバーに知らせるには、特別なメタデータエントリが( metadata.txt 中に)必要とされます


The example plugin discussed here (with many more example filters) is available on github: QGIS HelloServer Example Plugin. You could also find more examples at https://github.com/elpaso/qgis3-server-vagrant/tree/master/resources/web/plugins or browsing the QGIS plugins repository.



    __init__.py    --> *required*
    HelloServer.py  --> *required*
    metadata.txt   --> *required*


This file is required by Python's import system. Also, QGIS Server requires that this file contains a serverClassFactory() function, which is called when the plugin gets loaded into QGIS Server when the server starts. It receives reference to instance of QgsServerInterface and must return instance of your plugin's class. This is how the example plugin __init__.py looks like:

# -*- coding: utf-8 -*-

def serverClassFactory(serverIface):
    from HelloServer import HelloServerServer
    return HelloServerServer(serverIface)


魔法が起こると、これは魔法がどのように見えるかであるところである:(例 HelloServer.py


Each QgsServerFilter implements one or more of the following callbacks:

次の例では、 サービス パラメーターが「HELLO」に等しい場合に HelloServer! を印刷する、最小限のフィルタを実装します:

from qgis.server import *
from qgis.core import *

class HelloFilter(QgsServerFilter):

    def __init__(self, serverIface):
        super(HelloFilter, self).__init__(serverIface)

    def responseComplete(self):
        request = self.serverInterface().requestHandler()
        params = request.parameterMap()
        if params.get('SERVICE', '').upper() == 'HELLO':
            request.setHeader('Content-type', 'text/plain')

フィルタは、次の例のように serverIface に登録する必要があります:

class HelloServerServer:
    def __init__(self, serverIface):
        # Save reference to the QGIS server interface
        self.serverIface = serverIface
        serverIface.registerFilter( HelloFilter, 100 )

The second parameter of registerFilter sets a priority which defines the order for the callbacks with the same name (the lower priority is invoked first).

By using the three callbacks, plugins can manipulate the input and/or the output of the server in many different ways. In every moment, the plugin instance has access to the QgsRequestHandler through the QgsServerInterface. The QgsRequestHandler class has plenty of methods that can be used to alter the input parameters before entering the core processing of the server (by using requestReady()) or after the request has been processed by the core services (by using sendResponse()).



例のプラグインにはクエリ文字列からの入力パラメーターを変更する試験例を含んでいます、この例では新しいパラメーターが(既に解析された) parameterMap 中に注入され、するとこのパラメータはコアサービス(WMSなど)によって表示され、コアサービス処理の終わりではパラメーターがまだあることを確認します

from qgis.server import *
from qgis.core import *

class ParamsFilter(QgsServerFilter):

    def __init__(self, serverIface):
        super(ParamsFilter, self).__init__(serverIface)

    def requestReady(self):
        request = self.serverInterface().requestHandler()
        params = request.parameterMap( )
        request.setParameter('TEST_NEW_PARAM', 'ParamsFilter')

    def responseComplete(self):
        request = self.serverInterface().requestHandler()
        params = request.parameterMap( )
        if params.get('TEST_NEW_PARAM') == 'ParamsFilter':
            QgsMessageLog.logMessage("SUCCESS - ParamsFilter.responseComplete", 'plugin', QgsMessageLog.INFO)
            QgsMessageLog.logMessage("FAIL    - ParamsFilter.responseComplete", 'plugin', QgsMessageLog.CRITICAL)


 src/core/qgsmessagelog.cpp: 45: (logMessage) [0ms] 2014-12-12T12:39:29 plugin[0] HelloServerServer - loading filter ParamsFilter
 src/core/qgsmessagelog.cpp: 45: (logMessage) [1ms] 2014-12-12T12:39:29 Server[0] Server plugin HelloServer loaded!
 src/core/qgsmessagelog.cpp: 45: (logMessage) [0ms] 2014-12-12T12:39:29 Server[0] Server python plugins loaded
 src/mapserver/qgsgetrequesthandler.cpp: 35: (parseInput) [0ms] query string is: SERVICE=HELLO&request=GetOutput
 src/mapserver/qgshttprequesthandler.cpp: 547: (requestStringToParameterMap) [1ms] inserting pair SERVICE // HELLO into the parameter map
 src/mapserver/qgshttprequesthandler.cpp: 547: (requestStringToParameterMap) [0ms] inserting pair REQUEST // GetOutput into the parameter map
 src/mapserver/qgsserverfilter.cpp: 42: (requestReady) [0ms] QgsServerFilter plugin default requestReady called
 src/core/qgsmessagelog.cpp: 45: (logMessage) [0ms] 2014-12-12T12:39:29 plugin[0] HelloFilter.requestReady
 src/mapserver/qgis_map_serv.cpp: 235: (configPath) [0ms] Using default configuration file path: /home/xxx/apps/bin/admin.sld
 src/mapserver/qgshttprequesthandler.cpp: 49: (setHttpResponse) [0ms] Checking byte array is ok to set...
 src/mapserver/qgshttprequesthandler.cpp: 59: (setHttpResponse) [0ms] Byte array looks good, setting response...
 src/core/qgsmessagelog.cpp: 45: (logMessage) [0ms] 2014-12-12T12:39:29 plugin[0] HelloFilter.responseComplete
 src/core/qgsmessagelog.cpp: 45: (logMessage) [0ms] 2014-12-12T12:39:29 plugin[0] SUCCESS - ParamsFilter.responseComplete
 src/core/qgsmessagelog.cpp: 45: (logMessage) [0ms] 2014-12-12T12:39:29 plugin[0] RemoteConsoleFilter.responseComplete
 src/mapserver/qgshttprequesthandler.cpp: 158: (sendResponse) [0ms] Sending HTTP response
 src/core/qgsmessagelog.cpp: 45: (logMessage) [0ms] 2014-12-12T12:39:29 plugin[0] HelloFilter.sendResponse


同じ手法が、コアのサービスでなくカスタムサービスを利用するために利用できます:たとえば WFS SERVICE 要求または任意の他のコア要求を SERVICE パラメーターを別の何かに変更するだけでスキップできます、そしてコアサービスはスキップされ、それからカスタム結果を出力に注入してそれらをクライアントに送信できます(これはここで以下に説明される)。



import os

from qgis.server import *
from qgis.core import *
from qgis.PyQt.QtCore import *
from qgis.PyQt.QtGui import *

class WatermarkFilter(QgsServerFilter):

    def __init__(self, serverIface):
        super(WatermarkFilter, self).__init__(serverIface)

    def responseComplete(self):
        request = self.serverInterface().requestHandler()
        params = request.parameterMap( )
        # Do some checks
        if (request.parameter('SERVICE').upper() == 'WMS' \
                and request.parameter('REQUEST').upper() == 'GETMAP' \
                and not request.exceptionRaised() ):
            QgsMessageLog.logMessage("WatermarkFilter.responseComplete: image ready {}".format(request.infoFormat()), 'plugin', QgsMessageLog.INFO)
            # Get the image
            img = QImage()
            # Adds the watermark
            watermark = QImage(os.path.join(os.path.dirname(__file__), 'media/watermark.png'))
            p = QPainter(img)
            p.drawImage(QRect( 20, 20, 40, 40), watermark)
            ba = QByteArray()
            buffer = QBuffer(ba)
            img.save(buffer, "PNG")
            # Set the body

この例では SERVICE パラメーター値がチェックされます。そして着信要求が WMS GetMap であり、例外が以前に実行されたプラグインまたはコアサービス(この場合WMS)によって設定されていない場合、WMSで生成された画像が出力バッファから取得され、透かし画像が追加されます。最後のステップは、出力バッファをクリアして、新たに作成された画像で置き換えることです。実世界の状況では、どのような場合にもPNGを返すのではなく、要求された画像の種類を確認する必要もあることに注意してください。




    __init__.py    --> *required*
    AccessControl.py  --> *required*
    metadata.txt   --> *required*


This file is required by Python's import system. As for all QGIS server plugins, this file contains a serverClassFactory() function, which is called when the plugin gets loaded into QGIS Server at startup. It receives a reference to an instance of QgsServerInterface and must return an instance of your plugin's class. This is how the example plugin __init__.py looks like:

# -*- coding: utf-8 -*-

def serverClassFactory(serverIface):
    from MyAccessControl.AccessControl import AccessControl
    return AccessControl(serverIface)


class AccessControl(QgsAccessControlFilter):

    def __init__(self, server_iface):
        super(QgsAccessControlFilter, self).__init__(server_iface)

    def layerFilterExpression(self, layer):
        """ Return an additional expression filter """
        return super(QgsAccessControlFilter, self).layerFilterExpression(layer)

    def layerFilterSubsetString(self, layer):
        """ Return an additional subset string (typically SQL) filter """
        return super(QgsAccessControlFilter, self).layerFilterSubsetString(layer)

    def layerPermissions(self, layer):
        """ Return the layer rights """
        return super(QgsAccessControlFilter, self).layerPermissions(layer)

    def authorizedLayerAttributes(self, layer, attributes):
        """ Return the authorised layer attributes """
        return super(QgsAccessControlFilter, self).authorizedLayerAttributes(layer, attributes)

    def allowToEdit(self, layer, feature):
        """ Are we authorise to modify the following geometry """
        return super(QgsAccessControlFilter, self).allowToEdit(layer, feature)

    def cacheKey(self):
        return super(QgsAccessControlFilter, self).cacheKey()






def layerFilterExpression(self, layer):
    return "$role = 'user'"



以前よりも同じですが、(データベース内で実行) SubsetString を使用

def layerFilterSubsetString(self, layer):
    return "role = 'user'"




Return an object of type LayerPermissions, which has the properties:

  • canRead to see it in the GetCapabilities and have read access.

  • canInsert to be able to insert a new feature.

  • canUpdate to be able to update a feature.

  • canDelete to be able to delete a feature.


def layerPermissions(self, layer):
    rights = QgsAccessControlFilter.LayerPermissions()
    rights.canRead = True
    rights.canRead = rights.canInsert = rights.canUpdate = rights.canDelete = False
    return rights






def authorizedLayerAttributes(self, layer, attributes):
    return [a for a in attributes if a != "role"]




これは、 WFS-Transaction プロトコルで使用されています。


def allowToEdit(self, layer, feature):
    return feature.attribute('role') == 'user'



QGISサーバーは、このメソッド中に役割を返すことができる役割ごとにキャッシュを持っている能力のキャッシュを維持します。または None を返し、完全にキャッシュを無効にします。