JavaScript API

Securely Passing Parameters into a Tableau Viz at Load Time

The standard answer for enforcing user-based data entitlements in Tableau is to use Row Level Security, where the user is authenticated in Tableau Server and then tied into an “entitlements view” in the database so that the user only ever sees data they have access rights to.

However, we are very often asked about passing parameters in to the viz to filter down information directly at load time, often driven by an application that Tableau vizes are embedded in. This post is about a few methods of implementing this behavior, and the security implications of each of them.

Basics of Security

Everything must be HTTPS

I’ll start by saying, to do any of this securely, you need EVERY resource you are working with to be using the HTTPS protocol (latest TLS version). If anything is not HTTPS, you could be passing important information in the clear.

Using URL Parameters to set a Filter directly is NOT SECURE

You can use the URL Parameter syntax to directly set the values for a Filter on any field, but this is completely insecure. Why? Because the following two methods will clear any filter and reveal all of the rows of data. Unless you have the JS API turned off, there is no way to prevent this.


Sheet.clearFilterAsync(fieldName);
Sheet.applyFilterAsync(fieldName, "", tableau.FilterUpdateType.ALL);

Tableau Parameters are the (potentially) secure way to make an adjustable Data Source Filter

The only way to prevent a user from resetting a filter value is by making it a Data Source Filter.  Thankfully, you can use a Calculated Field for the Data Source Filter. If you use Tableau Parameters in the Calculated Field, the Parameter value(s) can be set to change what is filtered, and you will have a Data Source Filter that cannot be altered by the JS API (or the end user).

However, there are quite a few considerations to make this a truly secure method for setting filter values:

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Tableau and Write-Back – Together At Last

Editor’s Note: Huge thanks to special contributor Gordon Rose for this blog post.

Tableau helps people see and understand their data – and guarantees that it in the process, it will never make any changes to that data. Tableau is a strictly read-only technology. However, many customers want the ability to modify the data that lies behind a Tableau visualization (Viz), and then, either see those changes immediately reflected in the Viz and/or make other applications aware of those changes. With a small amount of supporting technology, Tableau’s read-only behavior can easily be integrated into so-called “write-back” use cases.

In this blog article, we’ll explore a way to do exactly that – one in which the write-back components are external to the Viz. An alternative approach is one in which those components are more tightly integrated into the Viz itself – that’s for a later blog article to explore. Ideally you will find that you can use one of these two approaches as a launching point for the development of your own write-back use case.

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Using the JavaScript API without Embedding

Tamás Földi always has amazing stuff, but this one really blows my mind- Tableau JavaScript API without Embedding .

Using the Web Data Connector to publish arbitrary extra content to Tableau Server is pretty amazing when you think about it; it also works for embedding web edit in an iframe.

Update for more recent Tableau Server versions (2017-11-15):

We recently encountered a customer wanting to implement this functionality and they were having trouble accessing the getWorkbook() method of the Viz object. Apparently Tableau Server now makes the Viz object available prior to it being fully initialized, and any web content starts to load immediately. So if you want to use this technique, you should put in an interval check to keep trying until the workbook is actually available. It looks something like this:


var myInterval;
function start_timer(){
myInterval = setInterval(js_api_test, 200); //https://www.w3schools.com/jsref/met_win_setinterval.asp
}
function js_api_test() {
try {
var sheet = parent.parent.tableau.VizManager.getVizs()[0].getWorkbook().getActiveSheet(); //Error: "Unable to get property getWorkbook()"
clearInterval(myInterval); //https://www.w3schools.com/jsref/met_win_clearinterval.asp
console.log("Successfully retrieved Tableau sheet object");

// start doing anything else you'd like to do here

//
}
catch (err) {
console.log("No dice!");
}
}

You would place a call to the start_timer() function in the onload function of the body tag of your HTML page. Rather than jump directly into the code, you start a repeating interval timer that puts in a bit of delay, and will retry until it actually gets the workbook object. Once that object is found, the interval is cleared and you can start doing whatever you want relative to the viz the page is embedded within.

 

Using getData in Tableau 10 to create tables from any Viz

Tableau 10’s JavaScript API has a new getData interface which allows you to get summary and underlying data directly as JavaScript objects. I’ve already shown a use case to use these methods for simply grabbing values. But a wider use case is creating an HTML table from any Tableau visualization, particularly if 508 compliance requires that you make all data available via a screen reader. Even if you don’t need compliance, you may just want to control how Tableau displays its underlying data. The full working example is here on GitHub.

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Reverting to the Original View through the JavaScript API

An interesting use case came in from a customer today, asking about something that is hinted at in the documentation of the JavaScript API, but not fully spelled out. They wanted to know how to replicate the ‘Original View’ button in the toolbar. After a bit of testing, I found out something new and not particularly well documented.

The Workbook class of the JS API has the methods for working with the CustomViews, to know which exist, to choose one, or to save a new one. All good — but how to do you interact with the ‘Original View’?

You can do Workbook.getCustomViewsAsync() to an Array of CustomView objects, which have properties which you can use to load any particular one. But interestingly, the ‘Original View’ does not come through in this array; if there are no custom views, the array is empty, and the ‘Original View’ does not appear even after some custom views have been created.

The setCustomViewAsync() method takes a string Name parameter, which will make the workbook switch to the custom view with that name (You can get this name using the getName() method of any CustomView object). However, passing the string ‘Original View’ does not work; you will get an error.

After some testing, I found that if you use the setCustomViewAsync() method without passing any parameter for name, it reverts back to the Original View. I realize this is not clear at all from the documentation, but I’ve tested it out and it appears to work. So reverting back to the Original View is as simple as:


book = viz.getWorkbook();

book.setCustomViewAsync().then( function (e) { // do whatever...});

Embedding Multiple Tableau Views in a Single Page

The Tableau JavaScript API is flexible and lets you embed multiple views, each as its own Viz object, in a single page. You can use this for multiple purposes:

  • Having a “single page application” that just loads the correct Tableau Server view
  • Loading multiple Views at the same time, allowing you to build a “dashboard of dashboards”
  • Have a second workbook that stays hidden until called (possibly triggered by an action on the first that a JS API event listener listens for)
  • Do smooth constant refreshes, by having two Viz objects of the same view, and moving one behind the other until it is has fully refreshed, then swapping it out

What do you need to make any of these work? At minimum, some mechanism for identifying which Viz object is which. In most cases, you’ll also want to track what should be visible at any given time, and what should be on top.

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