Sorry… what exactly is in this can again? by Paul Jerry, on Flickr

This is the most common thing you will see in an ATG Java class.

public class Foo extends GenericService

However 90% of the time it is extending GenericService so that the class has access to ATG’s logging capabilities.

This is overkill. The GenericService is much more than a logging service. As its name suggests it is meant to be extended by services, typically globally scoped. The main reason to extend GenericService is to get access to methods for controlling the service like doStartService and doStopService.

If you just want logging instead extend ApplicationLoggingImpl. It’s lighter weight and it’s clear why you are extending it. The only caveat is you have to remember to set the loggingIdentifier property in the properties file. For example:

# /betweengo/Foo
$class=com.betweengo.Foo
loggingIdentifier=betweengo.Foo

Another advantage of using ApplicationLoggingImpl is that the source is available in DAS/src/Java in the ATG installation unlike with GenericService.

Hopefully some people will read this post and on my next consulting project I won’t see such egregious uses of GenericService.

Tree Tutorial by eilonwy77

Sometimes when you are using an ATG powered website, e.g. Keds, you will see a _requestid parameter in your URL, e.g. http://www.keds.com/?_requestid=138580.

This occurs when the ATG code, typically a form handler, does a local redirect instead of a redirect. This is ATG’s own flavor of redirect which does a few extra things as described in the JavaDoc:

Sends a redirect response to the client using the specified redirect location URL. This function is similar to sendRedirect(), with the following two differences:

• The session ID is added to the URL if a valid cookie with the session ID is not found.
• If the URL is a relative URL (i.e., “login/error.html”), then the URL will be converted to a full absolute URL, as required by the HTTP specification. A relative URL is one that does not specify a protocol (e.g., “http:”).

In general, this function should be used when redirecting back to a page on the same site. If you are redirecting to a page on some other site, use the full absolute URL and call sendRedirect().

However this does not explain the mysterious _requestid parameter. Fortunately ATG’s Programming Guide does:

Preserving Request Scoped Objects on Redirects

If a request results in a redirect to a local page through the method HttpServletResponse.sendLocalRedirect(), the ATG platform treats the redirect request as part of the original request, and maintains any request-scoped objects associated with that request. To implement this, the ATG platform adds an additional query parameter named _requestid to the redirected URL.

Now you know what the _requestid parameter is and why it exists. And if you don’t want it then you the programmer should use a redirect instead of a local redirect.