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""" |
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I hold the lowest-level L{Resource} class and related mix-in classes. |
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""" |
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from zope.interface import implements |
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from twisted.web2 import iweb, http, server, responsecode |
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class RenderMixin(object): |
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""" |
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Mix-in class for L{iweb.IResource} which provides a dispatch mechanism for |
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handling HTTP methods. |
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""" |
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def allowedMethods(self): |
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""" |
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@return: A tuple of HTTP methods that are allowed to be invoked on this resource. |
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""" |
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if not hasattr(self, "_allowed_methods"): |
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self._allowed_methods = tuple([name[5:] for name in dir(self) if name.startswith('http_')]) |
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return self._allowed_methods |
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def checkPreconditions(self, request): |
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""" |
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Checks all preconditions imposed by this resource upon a request made |
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against it. |
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@param request: the request to process. |
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@raise http.HTTPError: if any precondition fails. |
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@return: C{None} or a deferred whose callback value is C{request}. |
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""" |
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if request.method not in ("GET", "HEAD"): |
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http.checkPreconditions(request) |
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method = getattr(self, "preconditions_" + request.method, None) |
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if method: |
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return method(request) |
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def renderHTTP(self, request): |
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""" |
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See L{iweb.IResource.renderHTTP}. |
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This implementation will dispatch the given C{request} to another method |
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of C{self} named C{http_}METHOD, where METHOD is the HTTP method used by |
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C{request} (eg. C{http_GET}, C{http_POST}, etc.). |
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Generally, a subclass should implement those methods instead of |
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overriding this one. |
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C{http_*} methods are expected provide the same interface and return the |
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same results as L{iweb.IResource}C{.renderHTTP} (and therefore this method). |
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C{etag} and C{last-modified} are added to the response returned by the |
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C{http_*} header, if known. |
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If an appropriate C{http_*} method is not found, a |
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L{responsecode.NOT_ALLOWED}-status response is returned, with an |
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appropriate C{allow} header. |
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@param request: the request to process. |
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@return: an object adaptable to L{iweb.IResponse}. |
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""" |
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method = getattr(self, "http_" + request.method, None) |
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if not method: |
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response = http.Response(responsecode.NOT_ALLOWED) |
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response.headers.setHeader("allow", self.allowedMethods()) |
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return response |
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d = self.checkPreconditions(request) |
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if d is None: |
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return method(request) |
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else: |
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return d.addCallback(lambda _: method(request)) |
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def http_OPTIONS(self, request): |
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""" |
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Respond to a OPTIONS request. |
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@param request: the request to process. |
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@return: an object adaptable to L{iweb.IResponse}. |
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""" |
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response = http.Response(responsecode.OK) |
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response.headers.setHeader("allow", self.allowedMethods()) |
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return response |
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def http_TRACE(self, request): |
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""" |
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Respond to a TRACE request. |
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@param request: the request to process. |
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@return: an object adaptable to L{iweb.IResponse}. |
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""" |
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return server.doTrace(request) |
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def http_HEAD(self, request): |
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""" |
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Respond to a HEAD request. |
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@param request: the request to process. |
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@return: an object adaptable to L{iweb.IResponse}. |
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""" |
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return self.http_GET(request) |
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def http_GET(self, request): |
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""" |
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Respond to a GET request. |
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This implementation validates that the request body is empty and then |
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dispatches the given C{request} to L{render} and returns its result. |
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@param request: the request to process. |
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@return: an object adaptable to L{iweb.IResponse}. |
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""" |
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if request.stream.length != 0: |
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return responsecode.REQUEST_ENTITY_TOO_LARGE |
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return self.render(request) |
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def render(self, request): |
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""" |
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Subclasses should implement this method to do page rendering. |
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See L{http_GET}. |
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@param request: the request to process. |
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@return: an object adaptable to L{iweb.IResponse}. |
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""" |
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raise NotImplementedError("Subclass must implement render method.") |
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class Resource(RenderMixin): |
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""" |
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An L{iweb.IResource} implementation with some convenient mechanisms for |
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locating children. |
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""" |
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implements(iweb.IResource) |
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addSlash = False |
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def locateChild(self, request, segments): |
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""" |
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Locates a child resource of this resource. |
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@param request: the request to process. |
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@param segments: a sequence of URL path segments. |
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@return: a tuple of C{(child, segments)} containing the child |
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of this resource which matches one or more of the given C{segments} in |
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sequence, and a list of remaining segments. |
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""" |
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w = getattr(self, 'child_%s' % (segments[0], ), None) |
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if w: |
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r = iweb.IResource(w, None) |
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if r: |
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return r, segments[1:] |
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return w(request), segments[1:] |
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factory = getattr(self, 'childFactory', None) |
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if factory is not None: |
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r = factory(request, segments[0]) |
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if r: |
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return r, segments[1:] |
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return None, [] |
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def child_(self, request): |
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""" |
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This method locates a child with a trailing C{"/"} in the URL. |
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@param request: the request to process. |
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""" |
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if self.addSlash and len(request.postpath) == 1: |
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return self |
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return None |
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def putChild(self, path, child): |
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""" |
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Register a static child. |
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This implementation registers children by assigning them to attributes |
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with a C{child_} prefix. C{resource.putChild("foo", child)} is |
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therefore same as C{o.child_foo = child}. |
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@param path: the name of the child to register. You almost certainly |
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don't want C{"/"} in C{path}. If you want to add a "directory" |
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resource (e.g. C{/foo/}) specify C{path} as C{""}. |
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@param child: an object adaptable to L{iweb.IResource}. |
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""" |
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setattr(self, 'child_%s' % (path, ), child) |
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def http_GET(self, request): |
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if self.addSlash and request.prepath[-1] != '': |
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return http.RedirectResponse(request.unparseURL(path=request.path+'/')) |
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return super(Resource, self).http_GET(request) |
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class PostableResource(Resource): |
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""" |
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A L{Resource} capable of handling the POST request method. |
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@cvar maxMem: maximum memory used during the parsing of the data. |
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@type maxMem: C{int} |
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@cvar maxFields: maximum number of form fields allowed. |
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@type maxFields: C{int} |
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@cvar maxSize: maximum size of the whole post allowed. |
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@type maxSize: C{int} |
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""" |
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maxMem = 100 * 1024 |
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maxFields = 1024 |
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maxSize = 10 * 1024 * 1024 |
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def http_POST(self, request): |
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""" |
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Respond to a POST request. |
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Reads and parses the incoming body data then calls L{render}. |
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@param request: the request to process. |
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@return: an object adaptable to L{iweb.IResponse}. |
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""" |
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return server.parsePOSTData(request, |
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self.maxMem, self.maxFields, self.maxSize |
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).addCallback(lambda res: self.render(request)) |
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class LeafResource(RenderMixin): |
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""" |
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A L{Resource} with no children. |
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""" |
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implements(iweb.IResource) |
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def locateChild(self, request, segments): |
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return self, server.StopTraversal |
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class RedirectResource(LeafResource): |
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""" |
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A L{LeafResource} which always performs a redirect. |
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""" |
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implements(iweb.IResource) |
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def __init__(self, *args, **kwargs): |
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""" |
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Parameters are URL components and are the same as those for |
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L{urlparse.urlunparse}. URL components which are not specified will |
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default to the corresponding component of the URL of the request being |
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redirected. |
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""" |
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self._args = args |
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self._kwargs = kwargs |
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def renderHTTP(self, request): |
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return http.RedirectResponse(request.unparseURL(*self._args, **self._kwargs)) |
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class WrapperResource(object): |
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""" |
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An L{iweb.IResource} implementation which wraps a L{RenderMixin} instance |
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and provides a hook in which a subclass can implement logic that is called |
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before request processing on the contained L{Resource}. |
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""" |
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implements(iweb.IResource) |
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def __init__(self, resource): |
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self.resource=resource |
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def hook(self, request): |
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""" |
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Override this method in order to do something before passing control on |
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to the wrapped resource's C{renderHTTP} and C{locateChild} methods. |
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@return: None or a L{Deferred}. If a deferred object is |
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returned, it's value is ignored, but C{renderHTTP} and |
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C{locateChild} are chained onto the deferred as callbacks. |
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""" |
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raise NotImplementedError() |
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def locateChild(self, request, segments): |
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x = self.hook(request) |
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if x is not None: |
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return x.addCallback(lambda data: (self.resource, segments)) |
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return self.resource, segments |
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def renderHTTP(self, request): |
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x = self.hook(request) |
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if x is not None: |
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return x.addCallback(lambda data: self.resource) |
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return self.resource |
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__all__ = ['RenderMixin', 'Resource', 'PostableResource', 'LeafResource', 'WrapperResource'] |
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