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December 22, 2013

Trials or tribulation? Inside SharePoint 2013 workflows–Part 3

Filed under: Application Development,Business Analysis,Business Process Management,IAAS,oData,Process Improvement,REST,SharePoint,SharePoint 2013,Training,Troubleshooting,Workflow,Workflow Manager,Workflows — admin @ 6:47 pm

Hi and welcome to part 3 of my series of articles that take a peek under the hood of SharePoint 2013 workflows, while trying to answer the question of whether SharePoint 2013 workflows can enable citizen developers to go forth and solve business problems and catapault organisations to success. In part 1, I introduced you to Megacorp Inc and their need for a controlled documents approval workflow. In part 2, we created a basic SharePoint 2013 workflow that implements the logic outlined in the picture below. The workflow is not yet finished, but we did enough to be able to run it and learn from it, which brings us to this post.

Now I will tell straight up that our first test of this workflow is not going to work. The entire point of this series of articles is to show you *why* things do not always work what you need to do about it. As we progress, I hope that you will learn quite a bit about the operation of workflows in SharePoint 2013, as well as developing and troubleshooting them. After all, we all know that the best citizens are informed citizens!

So let’s get on with testing this particular workflow. We published it to the Documents library in part 2, so now we trigger it by selecting one of the files in the library. In this example, I will select one of the documents tagged as from Megacorp GM Foods. So using the filtering feature provided by metadata navigation, we just show the four documents owned by the Megacorp GM Foods division.

In this example, we will update the document called Burger Additives Standard. The workflow has not yet been set to automatically start, so we will need to manually trigger the workflow ourselves. To do so, click the ellipses next to the Burger Additives Standard document, and then click the ellipsis in the bottom right of the properties/preview window. This will show a second drop down menu. Choose Workflows from this menu as shown below.

Underneath the Start a New Workflow text, you will see the workflow we published in part 2 called Process Owner Approval. Clicking it will start the workflow on this document.

First sign of trouble…

After starting the workflow, the browser will redirect you back to the Documents library. At this point, we see our first sign of trouble. When a workflow is published on a list or library, a column is added that is used to track workflow progress. In this case, we started our workflow, but there is nothing displayed in the workflow status column and the workflow does not appear to run. Hmm… what gives?

When a workflow does not behave as you intended, the easiest way to troubleshoot is to use the workflow status page. As it happens, you have already seen this page, because it is the same page where we started the workflow. So once again, we click on the ellipsis next to the burger additives standard document, click the ellipsis in the properties window and choose Workflows from the drop down menu.

Well look at that… it says the workflow is indeed started…

Clicking on the running workflow, we can see more detail which I have shown below. This screen also says that the workflow is started and nothing appears amiss. But then there is the little blue information symbol next to the Internal Status label. Hovering over this icon displays yet more information. This time, we see an error that would stump many – the sort of error that an information worker would have to call up helpdesk for.

Retrying last request. Next attempt scheduled in less than one minute. Details of last request: HTTP InternalServerError to http://megacorp/iso9001/_vti_bin/client.svc/web/lists/getbyid(guid’a64bb9ec-8b00-407c-a7d9-7e8e6ef3e647′)/Items(7) Correlation Id: de95e312-e24b-42c3-9369-5bae68040219 Instance Id: 9ed3a11d-f665-4512-9b17-78850356c846

Okaaaay, so that error message is about as useful as Windows Vista. It shows an internal server error and a correlation ID. Furthermore, if you wait another minute or so, and then refresh the workflow status screen, it’s internal status is no longer started, but now has the status of Cancelled. You can see it for yourself below…

One again, clicking the little blue info button gives us more detail. Unfortunately, the detail consists of an even scarier appearing message than the previous one. This one looks nasty enough to freak out some SharePoint admins too. Check it out – it is pretty much useless in terms of conveying any information of value.

RequestorId: 8ad4a017-7e6f-0d0f-35d2-81c56a05b37c. Details: System.ApplicationException: HTTP 500 {“Transfer-Encoding”:[“chunked”],”X-SharePointHealthScore”:[“0″],”SPClientServiceRequestDuration”:[“211″],”SPRequestGuid”:[“3d7950b2-3d9d-47d9-a5fb-588bf02b9551″],”request-id”:[“3d7950b2-3d9d-47d9-a5fb-588bf02b9551″],”X-FRAME-OPTIONS”:[“SAMEORIGIN”],”MicrosoftSharePointTeamServices”:[“15.0.0.4420″],”X-Content-Type-Options”:[“nosniff”],”X-MS-InvokeApp”:[“1; RequireReadOnly”],”Cache-Control”:[“max-age=0, private”],”Date”:[“Sun, 17 Nov 2013 22:56:19 GMT”],”Server”:[“Microsoft-IIS\/8.0″],”X-AspNet-Version”:[“4.0.30319″],”X-Powered-By”:[“ASP.NET”]} at Microsoft.Activities.Hosting.Runtime.Subroutine.SubroutineChild.Execute(CodeActivityContext context) at System.Activities.CodeActivity.InternalExecute(ActivityInstance instance, ActivityExecutor executor, BookmarkManager bookmarkManager) at System.Activities.Runtime.ActivityExecutor.ExecuteActivityWorkItem.ExecuteBody(ActivityExecutor executor, BookmarkManager bookmarkManager, Location resultLocation)

So what the hell is going on here?

Unfortunately, both of the error messages above are virtually useless for most people and the only way to dig deeper is to delve into the SharePoint ULS logs. Of course, if you use Office 365 ~~you don’t have that luxury because accessing the ULS logs are not available to you – so your best option to figuring out errors like this is trial and error~~. you need to learn CSOM code to access the logs. For the rest of us living in on-premises or IaaS land, a quick search of the ULS logs for the file name “Burger additives standards” reveals the issue and the root cause. Check out the errors reported below – it should be quite clear…

SharePoint Foundation             General                           8kh7    High        The file “http://megacorp/iso9001/Documents/Burger additives standards.pdf” is not checked out. You must first check out this document before making changes.

SharePoint Foundation             General                           aix9j    High        SPRequest.AddOrUpdateItem: UserPrincipalName=i:0).w|s-1-5-21-1480876320-1123302732-2276846122-500, AppPrincipalName=I:0I.T|MS.SP.EXT|2CC54B18-3F9D-43A3-BE55-B3A81C045562@B9A66C21-F39D-42DB-B6CD-DE520B6C1C91 ,bstrUrl=http://megacorp/iso9001 ,bstrListName={A64BB9EC-8B00-407C-A7D9-7E8E6EF3E647} , bAdd=False , bSystemUpdate=False , bPreserveItemVersion=False , bPreserveItemUIVersion=False , bUpdateNoVersion=False ,pbstrNewDocId=00000000-0000-0000-0000-000000000000 , bHasNewDocId=False , bstrVersion=8 , bCheckOut=False ,bCheckin=False , bUnRestrictedUpdateInProgress=False , bMigration=False , bPublish=False , bstrFileName=<null>

SharePoint Foundation             CSOM                              ahjq1    High        Exception occured in scope Microsoft.SharePoint.SPListItem.UpdateWithFieldValues. Exception=Microsoft.SharePoint.SPException: The file “http://megacorp/iso9001/Documents/Burger additives standards.pdf” is not checked out. You must first check out this document before making changes. —> System.Runtime.InteropServices.COMException: The file “http://megacorp/iso9001/Documents/Burger additives standards.pdf” is not checked out. You must first check out this document before making changes.     at Microsoft.SharePoint.Library.SPRequestInternalClass.AddOrUpdateItem(String bstrUrl, String bstrListName, Boolean bAdd, Boolean bSystemUpdate, Boolean bPreserveItemVersion, Boolean bPreserveItemUIVersion, Boolean bUpdateNoVersion, Int32& plID, String& pbstrGuid, Guid pbstrNewDocId, Boolean bHasNewDo…    3b84d615-e006-4457-811a-0af089963216

So in case it is not clear from the above messages, we have an error stating that the file Burger additives standards is not checked out and that to make changes to the document, we need to check it out first. This raises several questions:

1. Why is the document library configured to require check-out?
2. Why is the workflow trying to change the document anyway? The workflow we created in part 2 does no action on the Documents library.
3. Why were the error messages so useless (which really hurts in Office365 scenarios)
4. How can we fix this problem?

Let’s examine each of these in turn…

1. Why is the document library configured to require check-out?

The first question is really easy to answer. When you create a site using the Document Center site template, the document library versioning settings enable the Require Check Out option as shown below. Therefore no changes can be made to this document unless the user making the change checks it out.

2. Why is the workflow trying to change the document anyway?

The second question is also easy to answer, but the answer is somewhat more complicated. When a workflow is associated to a list or content type, it adds a column to track the status of the workflow. In SharePoint 2013, the default behaviour is to update this column with whatever stage in the workflow currently being executed. Therefore, as soon as the workflow runs, and before it has run any of the actions, it attempts to update its stage to the document that it was triggered from. So looking at the images below, if things were working we should see the string “Stage 1” in the Process Owner Approval column for the document Burger additives standards. But since the document requires check-out to make a change, SharePoint prevents this from happening by design.

Some readers who are experienced with SharePoint Designer workflow might be thinking “easy… just use the check out item workflow action before you do anything else.”Unfortunately this won’t work for you because this issue gets triggered when the stage info is written to the workflow status column which happens before any actions run.

3. Why were the error messages so useless (which really hurts in Office365 scenarios)

The next question is why on earth wasn’t the true error able to be reported back to the workflow? After all, in the end, this was a clearly identified error in SharePoint, yet all we got was error messages that did not state the problem at all. This would have saved the effort of delving deep into the ULS logs and that is not even possible in Office 365.

The answer to this question is a little more complex and relates to how Workflow Manager and SharePoint interact with each other. Without getting into detail, the gist of the issue is that Workflow Manager uses REST webservice calls to do all of its operations on SharePoint content. Each and every workflow action (like the Log to History List) uses REST to talk to SharePoint to get the work done. While a detailed discussion of REST would take us too far afield, I have drawn you possibly the dodgiest ever diagram of this process ever to help you understand it. The main point with REST worth mentioning is that the intention of REST is to embrace the key protocols of the web, so a successful or failed request is conveyed via a HTTP status code. If you have ever experienced your browser giving you a 404 page not found, then you know what I mean when I speak of HTTP status codes.

Now look again at the gory detail of the error that was logged by the workflow. We see the following string amongst all the other stuff. “Details: System.ApplicationException: HTTP 500”. So what happened is when the workflow tried to update the document with its stage, the check-out requirement resulted in SharePoint sending back a HTTP Error 500 (server error) back to the workflow manager. Unfortunately for us, it did not send back the underlying cause of the error. Instead, the details of the response logged by workflow has all sorts of information about the HTTP request, but no hint to the underlying error. Sucks eh?

4. How can we fix this problem?

The final question was what we could do about this issue. There are two relatively easy ways, but before I do that, let me show you what happens if you check out the document and then attempt to run the workflow. While you might think this problem might go away, instead we get a friendly dialog box telling us to check the document back in before we attempt to start a workflow. Given that I couldn’t run this workflow because the item needed to be checked out, I had to laugh.

Anyways, the two options you have are to disable require check out on the Documents library or change the default behaviour of the workflow so that it does not write the stage back to the item that triggered the workflow. The first one is pretty easy – in the Versioning Settings of the Documents library, we change the Require documents to be checked out before they can be edited? option from Yes to No

The problem with the first option is that requiring check-out for controlled documents is likely to be a key requirement, so it is not an option in all circumstances. So the other option is to change the behaviour of the workflow itself so that it does not write its stage information back to the Documents library. Luckily for us, this is actually really easy to do. In SharePoint Designer 2013, there is an option to disable the updating of stage information. In the workflow settings screen, look for the option called Automatically update the workflow status to the current stage name and untick it.

Now unticking this box will get us past this error, but the problem now is that we have no easy way to track workflows, as this status update can be used in views on the Documents library to see which workflows are at a particular stage. For a complex workflow, or one that will be running on many items, not being able to see the status of the workflow would make life difficult. One workaround is to add a Check Out Item workflow action to the start of the workflow, and then use the Set Workflow Status action to update the status column on the current item as the workflow progresses. This will give us back the ability to track the workflow behaviour in the Documents library, but it will mean that a new version will be added to that Document each time the status updates. So another workaround is to log workflow status to some other list altogether (using the Create List Item action) and use that list for tracking and reporting instead.

Conclusion

I think that the separation of SharePoint and Workflow Manager into separate products is ultimately a good thing. It’s just a pity that one of the legacies of this change is an issue like what we covered in this post, where a relatively simple problem was exacerbated by poor reporting of errors between Workflow Manager and SharePoint. I guess this is part of the bigger price we pay – that of increased technical complexity via more moving parts. Hopefully an issue like this one can be addressed in a future service pack or update, because it is this sort of stuff that can cause people to lose some confidence and jump to the 3rd party solution perhaps prematurely. So if this issue was enough for you to think “pah – let’s go third party”, I have news for you. As you progress through this series we are going to deal with more complex issues than this one too.

Anyway, the point is that we have identified the cause of this particular issue and gotten past it, so we should be able to continue testing the workflow and marvel at our awesomeness. So in the next article, we will continue with testing our workflow and see what else SharePoint throws at us.

Thanks for reading

Paul Culmsee

www.hereticsguidebooks.com

Comments (16)

December 21, 2013

Trials or tribulation? Inside SharePoint 2013 workflows–Part 1

Filed under: Application Development,Business Analysis,Business Process Management,Information Architecture,Managed Metadata,oData,Process Improvement,REST,SharePoint,SharePoint 2013,SharePoint Designer,SPD,Training,Web Services,Workflow,Workflow Manager,Workflows — admin @ 3:18 pm

Hi all

Workflows are big business in SharePoint land, despite the capability of SharePoint Designer Workflows being a fairly weak link in the overall SharePoint value proposition. If this wasn’t the case, then products like Nintex or K2 would not be so popular and workflow vendors wouldn’t have the biggest booths at the average SharePoint conference.

One of the serious strategic advantages of going with the SharePoint stack is the amazing 3rd party ecosystem that flourishes around the base product. No other platform in the space has the level of 3rd party support that SharePoint enjoys. But while its nice to be able to have great options for serious SharePoint workflow development, with each successive version of SharePoint that comes out, there is always that hope that one can use the base functionality without having to jump straight away to the 3rd party tools. After all, it is quite common for organisations, having just gone to the time and expense of adopting SharePoint, to be dismayed that they have to part with yet more cash for 3rd party tools to address large functional gaps that were not apparent in the contrived product demos.

Another important trend being hidden by cloud hubris is the rise of the citizen developer. The CIO’s fountain of knowledge known as Gartner, stated that by 2014 25% of new business applications will be delivered by Citizen Developers. They defined citizen developers as “a user operating outside of the scope of enterprise IT and its governance who creates new business applications for consumption by others either from scratch or by composition.” Elaborating, Gartner stated that

“Future citizen-developed applications will leverage IT investments below the surface, allowing IT to focus on deeper architectural concerns, while end users focus on wiring together services into business processes and workflows. Furthermore, citizen development introduces the opportunity for end users to address projects that IT has never had time to get to — a vast expanse of departmental and situational projects that have lain beneath the surface.”

So with SharePoint 2013, Microsoft has indeed changed things up a notch in the workflow world. Is it enough to enable and empower citizen developers?

That is what this series aims to find out… First up, lets take a quick look at the forces we are going to be meddling with…

What’s new with SharePoint 2013 and workflow…

Workflow in SharePoint 2013 is significantly different from SharePoint 2010. It fact, it is essentially a completely separate product called Workflow Manager. Technically, Workflow Manager is not part of SharePoint at all – there is no “workflow” service application or “service on a server” to be found. Instead, it is a separate process that works by communicating with SharePoint over the HTTP protocol in various ways.

This means that we have the option of deploying Workflow Manager onto its own server, or set of servers (although for you smaller sites, it happily installs onto your SharePoint servers and coexists with the rest of SharePoint too). This loosely coupled model has scalability benefits as workflow load can now be separated from the rest of SharePoint. It also means badly behaved workflows are less likely to affect SharePoint sites because they run in a separate process or separate servers. 3rd party applications (think about solutions built using the SharePoint 2013 apps model here) can also interact and communicate with workflow manager separately to SharePoint. It also helps Microsoft to realise their strategy of “encouraging” everyone to their vision of a cloud-based happy place.

Now new does not always equate to good – and Microsoft have a bit of a dubious history with V1 products and technology. So in this series, I’d like to show you an example of what the SharePoint 2013 new workflow regime can do. The example that I am going to use for this set of articles is useful for this purpose for several reasons:

1. It is a common use-case that many organisations would find familiar – particularly those with compliance regimes
2. It demonstrates a fairly typical SharePoint consulting “oh crap” moment, where you realise your masterpiece of a solution is completely undone by an untested assumption or a SharePoint caveat that you forgot about.
3. It demonstrates a path to redemption that is an excellent utilisation of the new capabilities of SharePoint 2013 and Workflow Manager
4. It gives you a great sense as to whether workflows are a real developer, information worker or citizen developer tool. In other words, after reading this, you should have a good idea what you are getting yourself into!

I have a lot to cover, so this series will be multi-part. This first post will outline the scenario that we are dealing with.

The scenario: Document Control at Megacorp

Many organisations operate in industries where they are required to manage documentation in a systematic way. Documents that are subject to any sort of quality or compliance regime are often referred to as “Controlled Documents”. Typically, a controlled document will have an assigned responsible party who is accountable for the management (i.e. approving the issuing of updates) of that document.

To illustrate, consider the document control requirements of Megacorp Inc – a mythical multinational conglomerate with a vide variety of businesses in many different industries and locations. Megacorp is your typical diversified multinational, making everything from Iron Man suits to hamburgers. A managed metadata term set illustrating the Megacorp conglomerate structure can be seen below. If you look closely, Megacorp Inc, actually consists of several companies and each is structured differently. For example: Megacorp Pharmaceutical divides itself based on country and state jurisdiction, whereas Megacorp GM foods divides itself up on the particular food it is generically modifying.

So let’s say that Megacorp is maintaining ISO9001 certification for assurance purposes and therefore has to control their documents as I have stated above. Let’s create a SharePoint site called ISO9001 to handle this requirement. We perform the following steps:

Build a term set (called Megacorp Inc)that stores all of the Megacorp businesses (you can see that in the image above)
Create a site based on the built-in Document Center template
Create a managed metadata site column called Organisation and associate it to the Megacorp term set
Add the organisation column to the document library (called Documents) in the Document Center site
Enable Metadata Navigation on the Documents library and add the Organisation column as a hierarchy field

For those of you who are new to SharePoint, below are screenshots from those steps to help you with the above steps… I am not going through this stuff in detail, so hopefully this suffices…

Now that the above plumbing is done, a few documents have been added to the Documents library and tagged to their organisation. With Metadata Navigation enabled, we now have the easy means to browse and filter documents to the specific organisation who owns them as shown below…

So let’s now think through a workflow scenario. Each organisation that makes up Megacorp has a process owner and when a document is ready for publishing, the process owner needs to approve it. Now we could do this by adding a “Person or Group” column to the document library and call it “process owner.” But Megacorp has some additional considerations that need to be pondered…

1. They have thousands of documents in the library
2. The process owner is a role, not an individual person. For audit purposes, Megacorp wants to have a record of when a person was in a particular process owner role.

The reason this complicates things is twofold. If we use a person’s user account in Active directory for tagging the process owner, we can easily track when a process owner changes because it will show up in the version history of the documents. But the downside is that we would have to update each document individually when that process owner changes to someone else. Not to mention that we may not want this change to be a version change in the document itself.

Now I know what your thinking – “Just use an Active Directory Group instead of an account”. Yes, it is a good and logical suggestion, since a SharePoint or Active Directory group allows us to easily manage changes in personnel between roles by changing group members. But the downside is that we have no easy way to see the history of who was in the process owner role at a given time because SharePoint would see and store the group, not the members of that group.

So let’s try an alternative approach. We will make a custom list called “Process Owners” and add two columns to it. We will add the Organisation site column that we created and used earlier, and we will add the “Assigned To” column that is built-into SharePoint and used in task lists. This will give us a list of process owners for a given Megacorp company or division. Even better – if we turn on version history on the Process Owners list, we now have a record of who was in the process owner role at any given time because it will show up in the changes in the “Assigned to” field over time.

The image below illustrates the Process Owners list.

So to summarise, we have a document library where all documents are tagged to the organisation that they belong to. We have a list of the process owners for each organisation. To better visualise this, I have drawn an xmind map to show you the Information Architecture of the Megacorp document control site

Now we turn our attention to the document approval workflow. It should be able to:

Look at a document and determine the Organisation that a document belongs to
Look in the process owners list for that organisation and then determine the process owner for the organisation by grabbing the information in the “Assigned To” field
Create an Approval task for the Process owner to approve the release of a controlled document.

Now this all sounds straightforward enough in theory but as we will see as this series progresses, when it comes to SharePoint, theory and reality are two very different things. So in part 2, we will build out the workflow..

Thanks for reading

Paul Culmsee

www.heretisguidebooks.com

Comments (0)

September 23, 2013

How to filter on a Managed Metadata column via REST in SharePoint 2013

Filed under: Application Development,Fiddler,oData,REST,SharePoint,Troubleshooting,Web Services — admin @ 9:13 pm

Pardon the pun, but I just had a ‘clever workaround’ moment with SharePoint’s oData/REST implementation when it comes to filtering list items based on taxonomy (managed metadata) columns. Now I do not consider myself a developer, so this article is probably a little verbose for some readers, but should be helpful to power users or IT pros.

Here is an example term set called FilterDemo. You can see two levels of hierarchy.

Take the scenario of a custom list (called TestFilter) with a managed metadata column (called FilterDemo) that links to the above term set. Let’s also assume there are 3 entries in it as follows:

Title	FilterDemo
A	A1
B	B3
C	Category A

Using the wonders of the REST API, I am able to get access to all items in the list via the following URL:

http://site/_api/web/lists/getbytitle(‘TestFIlter’)/Items

If you execute that, and IE is has “feed reading view” turned off, you will get back lots of scary looking XML. If you collapse it though, you will see three entry tags in it. One for each item in the TestFilter list.

<?xml version=”1.0″ encoding=”utf-8″ ?>

– <feed xml:base=http://site/_api/ xmlns=”http://www.w3.org/2005/Atom“ xmlns:d=”http://schemas.microsoft.com/ado/2007/08/dataservices“ xmlns:m=”http://schemas.microsoft.com/ado/2007/08/dataservices/metadata“ xmlns:georss=”http://www.georss.org/georss“ xmlns:gml=”http://www.opengis.net/gml“>

+ <entry m:etag=”“2”“>

+ <entry m:etag=”“3”“>

+ <entry m:etag=”“1”“>

</feed>

Using more wonders of REST (and oData), I can change the URL to filter my results so that I only get matching items back. For example: here I am filtering on Items where the Title field has “A” in it.

http://site/_api/web/lists/getbytitle(‘Testfilter’)/Items/?$filter=Title eq ‘A’

Now we get back just the one entry matching that criteria…

<?xml version=”1.0″ encoding=”utf-8″ ?>

+ <entry m:etag=”“2”“>

Okay, so there is nothing earth shattering about what I just did above and its well documented in various places. But look what happens when I try and filter items in the list based on the FilterDemo column which is Managed metadata based…

http://site/_api/web/lists/getbytitle(‘Testfilter’)/Items?$filter=FilterDemo eq ‘A1’

Boom! Browser returns an error. If I do the same thing using Fiddler to look at the trace, it reports a HTTP/1.1 400 Bad Request error.

So I start digging and come across articles from Phil Harding and Serge Luca informing me that Taxonomy columns are unsupported via REST. I got my hopes up when I came across an Andrew Connell article on filtering lookup fields, since behind the scenes the taxonomy field is actually a lookup field, but in the comments section, it seemed to confirm that this wasn’t doable. All seemed lost…

But in reading MSDN’s REST articles, I had a vague recollection that CAML could be done via REST queries. I knew that using CAML, it was indeed possible to filter taxonomy columns. I proved it using CAML Designer 2013, connecting to the TestFilter list and filtering it successfully using the following XML…

<Where>
   <Eq>
      <FieldRef Name='FilterDemo' />
      <Value Type='TaxonomyFieldType'>A1</Value>
   </Eq>
</Where>

So, armed with this knowledge, I came across an MSDN forum thread where a tantalising clue was offered. Christophe Humbert asked whether CAML queries could be done via the REST API and Erik C. Jordan provided this nugget of wisdom:

I was able to get the following to work:

POST https://<site>/_api/web/Lists/GetByTitle(‘[list name]’)/GetItems(query=@v1)?@v1={“ViewXml”:”<View><Query>[other CAML query elements]</Query></View>”}

Editors node: I will be a little verbose at this point in case you are not a developer or overly familiar with REST.

This approach looked exactly what I needed and I thought this was worth a shot, but since the remedy is a HTTP POST rather than a GET, I couldn’t do it with Internet Explorer, so I loaded up fiddler, and used the Composer function. I crafted the following POST with an empty CAML query as a test…

http://site/_api/Web/lists/getByTitle(‘TestFilter’)/GetItems(query=@v1)?@v1={“ViewXml”:”<View><Query></Query></View>”}

And this is the response I got…

HTTP/1.1 411 Length Required

A quick bit of googling, and I realise that some HTTP queries require the use of a ‘Content-Length‘ field in the HTTP header. The standard states that: “Any Content-Length greater than or equal to zero is a valid value”, so I tried this figure as shown below:

And this time I get the response:

HTTP/1.1 403 FORBIDDEN (The security validation for this page is invalid and might be corrupted. Please use your web browser’s Back button to try your operation again).

Another quick bit of googling I discover that I am missing another required HTTP header in my POST request. This is called the X-RequestDigest and it holds something called the form digest. The form digest improves SharePoint security because it is specific to a specific user, site and limited to a certain time frame. You need to request a form digest and then pass it back to SharePoint for subsequent calls. To get hold of the form digest, you have to make another REST call which generates one. This is done by making a POST request with an empty body to http://site/_api/contextinfo and extracting the value of the “d:FormDigestValue” node in the information returned. In fiddler it looks like the following…

If you look at the returned content from calling the _api/contextinfo method above, I have highlighted FormDigestValue. In Fiddler, copy this value into the Request headers section of the composer and retry the CAML request:

Now if you execute the request, we get data!

HTTP/1.1 200 OK

If you look a the raw results in fiddler, you will see a whole bunch of scary XML. If you examine the results using the XML parser built into Fiddler as shown in the image below, you will see very similar output to my original REST request that I started this article with – 3 entries in this list. It worked!

So now let’s add our CAML query into the XML and see if we can make it work. Recall that I successfully tested this query via the following CAML…

<Where> <Eq> <FieldRef Name=’FilterDemo’ /> <Value Type=’TaxonomyFieldType’>A1</Value> </Eq> </Where>

So I construct the following URL and paste into the Fiddler constructor:

http://site/_api/Web/lists/getByTitle(‘TestFilter’)/GetItems(query=@v1)?@v1={“ViewXml”:”<View><Query><Where> <Eq> <FieldRef Name=’FilterDemo’ /> <Value Type=’TaxonomyFieldType’>A1</Value> </Eq> </Where> </Query></View>”}

With great excitement, I clicked “Execute” and received….

HTTP/1.1 400 Bad Request

Ah crap! Unfortunately I could not find a single example of this form of REST query to SharePoint, but I got a hint to the problem from Fiddler itself. It wasn’t happy with my request at all, showing the request as red.

Clearly I was doing something wrong, and being a non-developer I figured I wasn’t encoding things properly. So after some trial and error, I worked out that spaces were the issue. So where I was able to remove them I did, and those that I couldn’t, I encoded like so:

http://site/_api/Web/lists/getByTitle(‘TestFilter’)/GetItems(query=@v1)?@v1={“ViewXml”:”<View><Query><Where><Eq><FieldRef%20Name=’FilterDemo’/><Value%20Type=’TaxonomyFieldType’>A1</Value></Eq></Where></Query></View>”}

At this point fiddler stopped showing me an angry red colour and I clicked the Execute button. Wohoo! It works! Below you can see a single matching entry, just like my example when I filtered on Title column using the $filter parameter.

Expanding the XML indeed confirms it has matched term A1. Smile

Conclusion

While I was happy that I found a way to use REST to filter a list based on a Taxonomy column, I’m sure this method offers some interesting opportunities in various other scenarios.

In my company Seven Sigma, we have a worn-out post-it note that has the words “Alpha SharePoint Developer” written on it. This gets stuck to the office of whoever does the coolest coding trick and I’m happy to report that this little effort netted me the Alpha developer prize for the first time ever, principally because I then used this approach with SharePoint Designer 2013 workflows and it worked really well. In fact it worked so well that I have decided that using this with the new capabilities of SPD workflows warrants a blog series of its own.

Until then, I hope that this approach works for you and happy REST’ing!

Thanks for reading

Paul Culmsee

www.hereticsguidebooks.com

www.sevensigma.com.au

Comments (34)

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