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Things I Rarely Use: sessionScope
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Jesse Gallagher    

As this post's title implies, I'm considering making this a series on XPages anti-patterns, but no promises there. In any event, this is a topic that's been stewing in my brain for a little while: my antipathy towards the session scope in XPages. Now, don't get me wrong: other than the "not reset on logout" thing that may be fixed by now, I have no technical qualms with sessionScope; it does what it says on the tin. However, I've often found that many people use it very frequently, whereas I have found fewer and fewer uses over time where it is appropriate. To set the stage, I use the various scopes in roughly this order by descending frequency: viewScope applicationScope flashScope requestScope sessionScope The main things that I use sessionScope for are things that truly make sense only for the current browser session, such as the current date range to view in a log-viewing app. Other than that, I generally don't use it for: Caches Though it's not wrong, per se, to use the session for this, I've found it better overall to use the applicationScope, either directly (applicationScope.put("someCachedValue", whatever)) or by putting a Map keyed by username in there. The latter gets the same user-specific cache benefits of sessionScope (and more reliable, too, due to the potential for switched authentication) while also having the benefit of keeping the cache if the user logs in from another device. This is particularly potent with Anonymous. This is not a hard-and-fast rule, though - you may decide otherwise for cache-size or other reasons. Primary Navigation or Context Unlike the previous one, this is a hard-and-fast rule: do not use sessionScope for important page context. The worst would be something like having an "open document" button that puts the desired document UNID (or, worse, note ID) in sessionScope and then navigates to the page. Never do this! Though XPage URLs are a continuing problem, they're still the correct place for target-document information. The rule of thumb is that you should be able to copy the URL any time, paste it into another browser, and be in basically the same place. Secondary Context By this I mean things like the active linksbar category for the current page. I've seen things like having a navigation bar link that sends the user to a certain page while also setting a sessionScope variable to indicate the active menu bar. This is a huge problem for a number of reasons: it's a maintenance nightmare (having to code every link to do this), it's just asking for bugs (links setting the wrong or no value), and it breaks completely when the user bookmarks the page or comes back after session expiration. It's technically better than the previous crime, but only barely. The correct place for this information is handled somewhere in the page structure, though the specifics get murky. I generally take a page from the Extension Library example DB and use a "navigationPath" properly on my layout control to define a slash-delimited hierarchy of navigation context. Page-to-Page Context I'm thinking of things like a task-tracking system where you're looking at a Client document and want to add a Task to them, providing the Client document's ID for context. This is another area where the URL is the correct choice: ending up with a URL like "/task.xsp?clientId=whatever" makes the intent ("create a new task for client with ID 'whatever'") clear and stable across visits. Overall, I think of sessionScope as the Petyr Baelish of XPage features: there are some cases where you have to deal with it, but you should generally consider it extremely unreliable and untrustworthy.

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http://frostillic.us/f.nsf/posts/824DCB0E5F68BCDF85257D0A00802EE9
Jul 03, 2014
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Recent Blog Posts
6
Side-Project Monday Evening
Tue, Jun 27th 2017 1:49p   Jesse Gallagher
Yesterday, in one of my various Slack chats, the topic of JShell - the Java 9 REPL - came up in the context of how useful it would be for XPages development. Being able to open up a "shell" into a running XPages application could be really useful in a lot of ways - and I think that the XPages Debug Toolbar has an SSJS-evaluate feature that would do something like this. Still, it got me looking around a bit, and I ran across Groovysh Server, which is a project that combines Apache's SSH
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Including a Headless DDE Build in a Maven Tree
Tue, Mar 14th 2017 4:45p   Jesse Gallagher
Most of my Domino projects nowadays have two components: a suite of OSGi plugins/features and at least one NSF. Historically, I've kept the NSF part separate from the OSGi plugin projects - I'll keep the ODP in the repo, but then usually also keep a recent "build" made by copying the database from my dev server, and then include that built version in the result using the Maven Assembly plugin. This works, but it's not quite ideal: part of the benefit of having a Maven project being au
9
That Java Thing, Part 17: My Current XPages Plug-in Dev Environment
Sun, Feb 26th 2017 4:23p   Jesse Gallagher
It's been a while since I started this series on Java development, but I've been meaning for a bit now to crack it back open to discuss my current development setup for plug-ins, since it's changed a bit. The biggest change is that, thanks to Serdar's work on the latest XPages SDK release, I now have Domino running plug-ins from my OS X Eclipse workspace. Previously, I switched between either running on the Mac and doing manual builds or slumming it in Eclipse in Windows. Having just t
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Slides From My Connect 2017 Presentations
Fri, Feb 24th 2017 9:29p   Jesse Gallagher
At this year's Connect, Philippe Riand and I co-presented two sessions: one on ways to integrate your apps into the Connections UI and one on Darwino's role for Domino developers. I've uploaded the slides to SlideShare: DEV-1430 - IBM Connections Integration: Exploring the Long List of Options DEV-1467 - Give a New Life to Your Notes/Domino Applications and Leverage IBM Bluemix, Watson, & Connections (effectively, "the Darwino session")
8
The State of Domino App Dev Post-Connect-2017
Fri, Feb 24th 2017 9:28p   Jesse Gallagher
I'm en route back from this year's IBM Connect in San Francisco, and this plane ride is giving me a good chance to chew over the implications for Domino developers. First off, I'll put my bias in this matter right up front: Darwino, which I've been working on and discussing quite a bit, is one of the three "chosen" vendors for app enhancement/modernization/what-have-you. So, while this post isn't going to be about Darwino specifically, it's certainly pertinent for me. In any case,
7
Reforming the Blog in Darwino, Part 2
Thu, Feb 16th 2017 8:41p   Jesse Gallagher
During the run-up to Connect next week, I turned my gaze back to my indefinite-term project of reforming this blog in Darwino. When last I left it publicly, I had set up replication between a copy of the database and a Darwino app. After that post, I did a bit of tinkering in the direction of building a (J)Ruby on Rails front-end for it, next to the "j2ee" project. That side effort may bear fruit in time (as I recall, I got the embedded web app serving default pages, but didn't implemen
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Connect 2017 Final Stretch
Wed, Feb 15th 2017 12:16p   Jesse Gallagher
IBM Connect 2017 is less than a week away, and I've been furiously prepping for a couple parts of what is promising to be a busy conference. On Monday, before the official kickoff of the conference, OpenNTF is co-hosting a Hackathon, where attendees will work on one of several potential projects. The goal is to learn about new development methods, work with new people, and hopefully kick off some useful open-source projects to boot. During the conference proper, I'll be presenting two se
5
December Is Self-Aggrandizement Month, Apparently
Sat, Dec 17th 2016 3:21p   Jesse Gallagher
It's been a busy month (couple of years, really), but the last few weeks in particular have involved a couple minor announcements that I'm quite appreciative for. On the 14th, IBM announced the 2017 class of IBM Champions for ICS, and they included me on the list. It's been a joy to be considered a Champion for the last few years, and 2017 promises to be an interesting year to continue that in our slice of the development world. Mere days later, IBM sent out notifications about Connect
6
The New Podcast is a Real Thing: WTF Tech Episode 1
Mon, Oct 31st 2016 10:31a   Jesse Gallagher
As intimated at the end of the last This Week in Lotus, Stuart, Darren, and I have launched a new podcast in a similar vein: WTF Tech. Since we're all in the IBM sphere, that'll be the natural starting point for the topics we cover, but it's not going to be IBM-focused as such. For this first episode, we lucked out and had a couple-weeks period chock full of announcements, so we had plenty of material. Give it a listen!
5
Cramming Rails Into A Maven Tree
Mon, Sep 26th 2016 1:25p   Jesse Gallagher
Because I'm me, one of the paths I'm investigating for my long-term blog-reformation project is seeing if I can get Ruby on Rails in there. I've been carrying a torch for the language and framework for forever, and so it'd be good to actually write a real thing in it for once. This has been proving to be a very interesting thing to try to do well. Fortunately, the basics of "run Rails in a Java server" have been well worked out: the JRuby variant of the language is top-notch and the




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