Yahoo YQL Web Service JSON data.uri Tutorial
Here is a tutorial that might be re-introducing you to the Yahoo Web Services called YQL, building on previous ones here at this blog. The name is the way it is because it simplified the API aspects of its functionality for the developer to concentrate on SQL, and I’m really supportive of this concept. You don’t have to output in JSON, as other data forms like XML are acceptable. Let’s see what Wikipedia says about YQL below.
Yahoo! Query Language (YQL) is an SQL-like query language created by Yahoo! as part of their Developer Network. YQL is designed to retrieve and manipulate data from APIs through a single Web interface, thus allowing mashups that enable developers to create their own applications.[1]
Initially launched in October 2008 with access to Yahoo APIs,[2] February 2009 saw the addition of open data tables from third parties such as Google Reader, the Guardian, and The New York Times.[3] Some of these APIs still require an API key to access them. On April 29th of 2009, Yahoo introduced the capability to execute the tables of data built through YQL using JavaScript run on the company’s servers for free.[3]
So this tutorial uses a YQL web service into the data emanating from its links to the data.uri web service database with Yahoo YQL website … thanks.
We’ve talked in passing about the data.uri concept before. In the case of an HTML img tag’s definition you can specify the src= value in three different ways …
- as an address via an http: or https: protocol URL such as http://www.rjmprogramming.com.au/MyBusinessUnidad/Welcome_files/logo.jpg (our default)
- as an address via a local file: protocol URL such as file:///Library/pgAgent/Desktop/dynamic_javascript.jpg accessing a local image on the local computer being used (like you can make happen when you access your web browser’s File->Open File… functionality)
- as a data uri value which is a way to fully define the image data there and then, using base64 data
What this data.uri Yahoo Yql web service is providing, is a way to create a data uri from an http: or https: URL definition of a media file (image in our thinking above) … but, please note there is a 25600 byte limit to the size of the media file.
In our application today we show you an HTML img tag of the data on the parent page (the Firefox browser Firebug add on is showing you the resultant data uri) with a Javascript code scenario …
var thedatauri = 'data:image/jpeg;charset=UTF-8;base64,<!-- base64 data -->';
var wo=window.open('', 'imagename.jpg', 'top=400,left=400,width=200,height=200,resizable=yes');
wo.document.write('<img src="' + thedatauri + '" />');
… arranged by today’s PHP code you could call data_uri_yql.php or try a live run. In that way the HTML img data of the resultant popup window has no reference to any particular address on the web and would be useful for document fidelity purposes perhaps, as we’ve discussed previously on the blog here, because there is no trail back regarding its metadata.
Good links for information regarding this tutorial (thanks) are:
- YQL Two Minute Tutorial from Yahoo
- Yahoo! Query Language from Wikipedia, as per quote above
- YQL Home Page from Yahoo
- YQL data.uri help from Yahoo
- YQL JSON Parsing Help from YQL forum
Another tool you should have in your armoury for jobs like this is the online JSON validator here. A generic JSON approach to issues could be:
- Type the URL you were given into a web browser address bar and have a look at it
- Type the URL you were given into http://jsonlint.com/ and have it validated
- Understand in your own mind what would be different about 1. to make it suitable
- Incorporate findings of 3. into massaging of data between file_get_contents and json_decode
If this was interesting you may be interested in this too.
