1"""HTTP servlets"""
2
3from time import gmtime, strftime
4
5from Servlet import Servlet
6
7
8class HTTPServlet(Servlet):
9    """A HTTP servlet.
10
11    HTTPServlet implements the respond() method to invoke methods such as
12    respondToGet() and respondToPut() depending on the type of HTTP request.
13    Example HTTP request methods are GET, POST, HEAD, etc.
14    Subclasses implement HTTP method FOO in the Python method respondToFoo.
15    Unsupported methods return a "501 Not Implemented" status.
16
17    Note that HTTPServlet inherits awake() and respond() methods from
18    Servlet and that subclasses may make use of these.
19
20    See also: Servlet
21
22    FUTURE
23      * Document methods (take hints from Java HTTPServlet documentation)
24    """
25
26
27    ## Init ##
28
29    def __init__(self):
30        Servlet.__init__(self)
31        self._methodForRequestType = {}  # a cache; see respond()
32
33
34    ## Transactions ##
35
36    def respond(self, trans):
37        """Respond to a request.
38
39        Invokes the appropriate respondToSomething() method depending on the
40        type of request (e.g., GET, POST, PUT, ...).
41        """
42        request = trans.request()
43        httpMethodName = request.method()
44        # For GET and HEAD, handle the HTTP If-Modified-Since header:
45        # if the object's last modified time is the same
46        # as the IMS header, we're done.
47        if httpMethodName in ('GET', 'HEAD'):
48            lm = self.lastModified(trans)
49            if lm:
50                lm = strftime('%a, %d %b %Y %H:%M:%S GMT', gmtime(lm))
51                trans.response().setHeader('Last-Modified', lm)
52                ims = request.environ(
53                    ).get('HTTP_IF_MODIFIED_SINCE') or request.environ(
54                    ).get('IF_MODIFIED_SINCE')
55                if ims and ims.split(';', 1)[0] == lm:
56                    trans.response().setStatus(304, 'Not Modified')
57                    return
58        method = self._methodForRequestType.get(httpMethodName)
59        if not method:
60            methName = 'respondTo' + httpMethodName.capitalize()
61            method = getattr(self, methName, self.notImplemented)
62            self._methodForRequestType[httpMethodName] = method
63        method(trans)
64
65    @staticmethod
66    def notImplemented(trans):
67        trans.response().setStatus(501, 'Not Implemented')
68
69    @staticmethod
70    def lastModified(trans):
71        """Get time of last modification.
72
73        Return this object's Last-Modified time (as a float),
74        or None (meaning don't know or not applicable).
75        """
76        return None
77
78    def respondToHead(self, trans):
79        """Respond to a HEAD request.
80
81        A correct but inefficient implementation.
82        """
83        res = trans.response()
84        w = res.write
85        res.write = lambda *args: None
86        self.respondToGet(trans)
87        res.write = w
88