Sakai Development: Post Ten

So now to work on the presentation side of things, using the velocity files. This is something new to me, so I'm going to start off by reading through a tutorial suggested by Andrew Martin, with reference to the Sakai content tool. The first thing to do is to find the velocity configuration, which is a file listed in the relevant web.xml file, and which turns out to be called (unsurprisingly) velocity.properties. This in turn tells me that the velocity templates are stored where I would expect them to be, in the sakai-src/content/content-tool/tool/src/webapp/vm directory, sorted into two sub-directories, content and resources (which is a directory containing templates for common fragments, judging by the file names). One which we probably want to emulate is content/chef_resources_deleteConfirm.vm, so I'll start by opening that. Basically, the intention is to extend it by adding a metadata form. (I'll also need to make an archiving version equivalent to content/sakai_resources_deleteFinish.vm, I think.)

This is also where I come across the Sakai language support mechanism:

$tlang.getString("del.del")

I'll have to follow that through and add an appropriate entry for archiving, at least for the English language - there aren't all that many languages I could add entries to apart from that one. This, "del.del1", and "gen.cancel" appear several times in the two files. The values in different languages are set in files in config/localization/bundles/src/bundle/org/sakaiproject/localization/bundle/content/ (according to grep -R), so I'll need to sort things there. The file content.properties is the list of default phrases to use, which effectively means American English. So I add in content.properties, which usefully also contains a set of Dublin Core term descriptions:

#Archive Vm
archive.confirm = Archive confirmation and metadata creation
archive.sure = Enter information which describes the collection you have selected, and check the resources listed are correct.
archive.archive = Archive
archive.form = Enter information which describes the collection you have selected, and check the resources listed are correct.
archive.metadatatable = Table allows the input of metadata to describe the collection of items for archiving.
archive.resourcetable = Table holds information about resources selected for archiving. Column headers contain descriptions of contents and links for sorting.

I may need to add more later, when the form itself takes shape properly. Next, the form for confirmation itself. I'll also need to alphabeticise, as that's how the properties file is organised. This will start out as a copy of the delete confirmation form. Most of the changes amount to altering the word "delete" to "archive", to match equivalent updates to the ResourcesAction script which processes these files.

Then the main part of the change, to add the metadata input table. The metadata table needs to come before the file listing, simply because we don't know how many files might be in the listing, and so how far down the page the listing table might reach; confusing if the submitter needs to scroll down several times to find it. It starts with a table tag, like that for the listing, but instantly I see a problem. The file listing table has class "listHier" (presumably hierarchical list), but that is obviously not going to be appropriate for the metadata part of the form. The easiest way to solve this (as the vm file is a fragment of HTML and doesn't have the CSS declarations in it, so finding the right CSS file might be awkward - especially as there are almost 300 of them in the Sakai source code) is to find a table which is the right type, and copy the style information from that. Looking at the tables in the content-tool VMs, there are three types: listHier, itemSummary and no declared class, the first two with or without classes "lines" (not sure what this will do) and labelindnt (indent labels, presumably). I'll try not declaring a class first, so that the table will just inherit the styles current at this point in the page where it is displayed. So I add a table and appropriate DC terms - noticing that Sakai's interpretation of the meaning of a couple of them appears to be slightly different from that of the SWORD library developers, judging by the descriptions of the fields in the vocabulary list.

On to the second form. The delete version of the form seems to be identical, which is sensible - it takes the reader back to the file listing, which would now be missing the deleted items. At least, I think that's what happens; the form has submission buttons, which is a bit strange if this is the case. What I think I want to see displayed here for the archiving is the result of the submission (and a summary of what has been entered by the user on the previous page). So I add appropriate context.put statements to ResourcesAction to display the metadata which has been sent off, and display the results as text.

It would be possible to display the status of the submission in real time, using JQuery and Ajax. But I decided that I probably don't have the time to set this up, and most deposits should be pretty quick. So I just want to get the receipt, check the status, and then (assuming that the status indicates a successful deposit) display the information in the receipt - or at least, some of it, as there are quite a lot of fields which might be included in a returned receipt by the SWORD2 server. The swordapp lists the following fields which may be set in a DepositReceipt object:

receipt.getStatusCode();
receipt.getLocation();
receipt.getDerivedResourceLinks();
receipt.getOriginalDepositLink();
receipt.getEditMediaLink();
receipt.getAtomStatementLink();
receipt.getContentLink();
receipt.getEditLink();
receipt.getOREStatementLink();
receipt.getPackaging();
receipt.getSplashPageLink();
receipt.getStatementLink("application/rdf+xml");
receipt.getStatementLink("application/atom+xml;type=feed");
receipt.getSwordEditLink();
receipt.getTreatment();
receipt.getVerboseDescription();

Without going back to the SWORD2 specification it is not immediately apparent what all these fields mean. First, though, is a field which is not strictly speaking part of the receipt, but tells us whether the deposit itself was successful (if it has the value 200, 201, or 202), or not. The SWORD2 specification lists a small number of error codes which a server could send, so I only need to process these (and provide a default response, just in case - I could understand the web server returning 500 or 404, neither of which are listed part of the specification but would indicate respectively a problem with the way the SWORD server is set up on the web server or an incorrect URL respectively). Some are provided for SWORD2 clients, rather than direct access by a human being using a web browser - to allow, for example, the editing of the metadata for the deposited item at the location of the client rather than needing to go through the repository interface; such things would not be relevant for our purposes. So I need to add code to the script to set appropriate information into the context, so it be available to Velocity, and then add code to the archiveFinish Velocity template to display them.

I'm now going to finally attempt a compilation. This is a make or break moment, as the outcome of the process will be used to decide whether it is worth going on to finish off the work or whether it will need to be left in an incomplete state while I go on to other things that the Research360 project needs.  First time, it complains about the missing swordapp library, which I installed. Then there's the irritating missing end bracket:

sakai-src/content/content-tool/tool/src/java/org/sakaiproject/content/tool/ResourcesAction.java:[6796,73] error: ')' expected

Easily fixed. At least, once I realise I'm looking at line 7696 not line 6796...

And then again, and I get hundreds of errors from files I've not even changed -

could not parse error message:   symbol:   variable Menu
  location: class AttachmentAction
/home/simon/work/sakai-src/content/content-tool/tool/src/java/org/sakaiproject/content/tool/AttachmentAction.java:339: error: cannot find symbol
  state.setAttribute(MenuItem.STATE_MENU, bar);
                     ^