RESTful web services: When to use HTTP PATCH method

HTTP is a very interesting method but just a few application, SOA or Enterprise Integration developers use all of its capabitities. POST and GET among all HTTP Methods are the most used Method followed by PUT. Yet not very used the PATCH method is very useful and it plays a so specific role that it worth understanding its semantics.

In order to better understand HTTP’s PATCH method let’s have a real-world inspired example. The following figure is a simplified version of a integration project that I’ve been working on.

Users  connect to the cloud-based Payroll System in order to do many activivies such as employee data management.  This system holds the “master data” for employees.

Now imagine everytime an employee data is created or edited in the Payroll System we have to send this new/edited data  (the “1” in the figure) to other systems such as a Sales/Remuneration system (the “2” in the figure), a Performance Appraisal System (the “3” in the figure) and so on (the “4” in the figure).

As described in one of my last posts When to use HTTP Post and HTTP PUT, both POST and PUT create or edit a full Resource Representation, i.e., when you have all of its data.

Bringing it to our Payroll example it means we would create a RESTful web service – in our Tibco ESB – based on POST/PUT  method if the Payroll would send not only the edited Employee data but all its data (all attributes). But that was not the case of the Payroll system I was integrating with. The Payroll sends only the edited data, I mean, if a employee move to another apartment in the same building the payroll would send just the Address’ complement without the street name, city, postal code and so on so forth. That’s why HTTP PATCH was created for!

While in a PUT/POST request, the enclosed entity is considered to be a modified version of the resource stored on the
origin server, and the client is requesting that the stored version be replaced. With PATCH, however, the enclosed entity contains a set of instructions describing how a resource currently residing on the origin server should be modified to produce a new version.

Therefore, the final result of the RESTful web services created in Tibco ESB for this project was:

  • POST /employee/id:  Creates a employee in the Payroll system;
  • PUT /employee/id: Broadcasts a message  so that all other systems replace a full employee data. Actually, this will only be used in the future in my project and we did not created it;
  • PATCH /employee/id: Broadcasts a message  so that all other systems update just a set of a employee’s data.

That’s all for today. I hope you now are able to make a better decision on when to use POST, PUT and PATCH when designing RESTful web services.


noSQL and SQL databases: Not an exclusive decision

When trying to find real-world noSQL modeling cases to get some inspiration I ran into the NoSQL Data Modeling Techniques from Highly Scalable Blog. After reading the post and its comments I remembered the discussions around one Semantic Web class I attended last year at NCE-UFRJ. During that class we discussed the future of Triple Stores and that maybe OLTP systems would never leave the relational model and start using Triple Stores. Maybe representing data as RDF would be just another way of representing data the way OLAP systems do.

Almost everytime people talk about noSQL database they end up comparing it to SQL database and the relational model. My opinion at the moment is that it’s not an exclusive (XOR) decision. Since everybody say noSQL databases are better in high traffic/load evironments and SQL databases are better in OLTP env (where data change very frequently), we should take advantage of both at the same time. I mean, let’s have a noSQL database be another form of  data representation that is also in relational databases.

I will try to find how Facebook, Foursquare, Twitter etc use noSQL and SQL/Relational databases. If you see any article, presentation or post that talks about how the use such databases types, or if you have used both together please, share it here by posting a comment. It would be better if it shows an end-to-end architecture using both and not just a peace of it, ok?!

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