JSON and XML Tutorial - Part 1

If you're working with cloud services, or probably any kind of services, you're most likely working with JSON, XML (e.g. SOAP web services) or both. Although TDI provides specific components for handling web services, there is an easier approach to deal with both formats quickly and flexibly - and in the exact same way - if you're ready to do a little scripting. This is a quick tutorial to get you started with TDI's hierarchical Entry features - or hEntry for short.

As an experienced TDIer, you know that data in the system is carried around in Entry objects. Each Entry holds zero or more named Attributes. Each Attribute contains zero or more values.  Each value is a specific Java object used to represent the actual data content of that Attribute. We'll call this a 'flat Entry', since it represents a one dimensional list of Attributes - like a directory entry or a database table.

As of version 7, the Entry now has an hierarchical mode to represent a tree of data. hEntry mode is enabled automatically when you create an Entry based on hierarchical data, for example parsing XML or JSON. You can also explicitly call the enableDOM() method of an Entry, which then makes the DOM Interface functionality active and available. Or you can just add hierarchical attributes to it.

hentry = system.newEntry() // hentry is still flat
hentry.root = null // now it has a single attribute
hentry.root.branch = null // it's become hierarchical now
hentry.root.branch.leaf = "Green" // add a node with a text value

The above script creates a tree of data in the form of an hEntry. You can get the XML representation like this:

task.logmsg(hentry.toXML())

Here is the output:

<root>
  <branch>
  <leaf>Green</leaf>
  </branch>
</root>

And produce the JSON version like this:

task.logmsg(hentry.toJSON())

Which gives you the following:

{"root":{"branch":{"leaf":"Green"}}}

At this point it might help to know a little about how DOM (the XML Document Object Model) works. Here is where I learned about it: http://www.w3schools.com/dom/

In short, the DOM Model describes how an XML document is organized into a tree structure, and the DOM Interface provides methods for reading, searching and manipulating the leaves and branches of this tree. JSON is another way of describing hierarchical data. Once you have converted hierarchical data (either XML or JSON) into an hEntry then you use the DOM Interface methods to work with the data.

The Entry object provides a couple of static methods for turning hierarchical data into an hEntry: fromJSON() and fromXML(). Since they are static methods, this means you can call them using either an existing Entry object - e.g. work.fromJSON() - or by using the Class itself: com.ibm.di.entry.Entry.fromJSON(). Since you have methods for turning an hEntry into an XML or JSON representation, this makes JSON to XML conversion as simple as:

xmlString = work.fromJSON(jsonString).toXML()

And note that the above snippet will not change the contents of work. We're just making use of the static methods.

So much for the theory. You can easily play with this using the Javascript View at the bottom of your TDI Workbench, or by firing up the Debugger. Stay tuned for the next part of this discussion.