#912 new
Mark Piper

Loss of precision in Http.Request.isModified

Reported by Mark Piper | June 14th, 2011 @ 09:54 PM

Consider this test case:

    public void lossOfPrecisionCausesIsModifiedIssue() throws Exception {
        Http.Request request = newRequest();

        Date now = new Date();
        String etag = "etag";

        String httpFormatDate = Utils.getHttpDateFormatter().format(now);

        request.headers.put("if-modified-since", new Http.Header("if-modified-since", httpFormatDate));
        request.headers.put("if-none-match", new Http.Header("if-none-match", etag));

        //Checking against the same time should mean the request is not modified 
        //this fails
        assertFalse(request.isModified(etag, now.getTime()));

        //this works, because date is normalised first
        assertFalse(request.isModified(etag, Utils.getHttpDateFormatter().parse(Utils.getHttpDateFormatter().format(now)).getTime()));

The problem here is that request.isModified takes a long (i.e. millisecond precision), but that needs to be converted to an HTTP date for the header (second precision). Therefore, converting the HTTP date back into a long will always result in a number that is rounded down from the original. For instance, if now.getTime() = 1308087414635, converting to a HTTP date and then back to a long gives a result of 1308087414000.

Potentially, request.isModified needs to normalise the passed-in long to an HTTP format date first.

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