Generating a response – Apple WebObjects 3.5 User Manual
Page 53
Request-Handling Methods
53
following action method, the “CreditCard” component sets the
verified
session variable to YES when the user has supplied valid credit information
and returns the user to the original request page to try again.
- verifyUser {
if ([self isValidCredit]) {
[[self session] setVerified:YES];
return [[self application] pageWithName:nameOfNextPage];
}
return nil;
}
Limitations on Direct Requests
Users can access any page in an application without invoking an action. All
they need to do is type in the appropriate URL. For example, you can
access the second page of HelloWorld without invoking the
sayHello
action by
opening this URL:
http://serverhost/cgi-bin/WebObjects/Examples/HelloWorld.woa/-/Hello.wo/
When a WebObjects application receives such a request, it bypasses the
user-input (
takeValuesFromRequest:inContext:
) and action-invocation
(
invokeActionForRequest:inContext:
) phases because there is no user input to store
and no action to invoke. As a result, the object representing the requested
page—Hello in this case—generates the response.
By implementing security mechanisms in
invokeActionForRequest:inContext:
, you
can prevent users from accessing pages without authorization, but only if
those pages are not directly requested in URLs. To prevent users from
directly accessing pages in URLs, you must implement another strategy.
Generating a Response
The
appendToResponse:inContext:
method is invoked in the final phase of the
request-response loop, during which the application generates HTML for
the response page. You can override this method to add to the response
content or otherwise manipulate the HTTP response. For example, you
can add or modify the HTTP headers as in the following example:
- appendToResponse:aResponse inContext:aContext
{
[super appendToResponse:aResponse inContext:aContext];
[aResponse setHeader:@"True"
forKey:@"dshttpd-NoAutomaticFooter"];
}
In a similar manner, you can use
appendToResponse:inContext:
to add text to the
response content. In the following example, a component’s