vRealize Automation 7.x is currently in a sort of ‘split brain’ where there exists two data models which can be used to interact with vRA objects. One is objects that are backed by the Cafe appliance / PostgreSQL database and the other which uses the older, entity framework (IaaS servers).
This post is going to focus on the entity framework, which is still very relevant when working with this version of vRA. There are many things that still do not exist in the newer data model, such as custom properties and data collection. I still see vRO/vRA developers struggle with this, so I hope to help improve the situation.
The Entity Framework
When I first worked with vRA, I struggled to understand how objects were stored and manipulated in the database. I often came across a common object class called an entity. I later discovered that all objects stored in the vRA database are considered ‘entities‘. This is because vRA has been developed with Microsoft’s “Entity Framework“. A brief description of this taken from http://www.entityframeworktutorial.net
The Microsoft ADO.NET Entity Framework is an Object/Relational Mapping (ORM) framework that enables developers to work with relational data as domain-specific objects, eliminating the need for most of the data access plumbing code that developers usually need to write. Using the Entity Framework, developers issue queries using LINQ, then retrieve and manipulate data as strongly typed objects. The Entity Framework’s ORM implementation provides services like change tracking, identity resolution, lazy loading, and query translation so that developers can focus on their application-specific business logic rather than the data access fundamentals.
Entity framework is an Object/Relational Mapping (O/RM) framework. It is an enhancement to ADO.NET that gives developers an automated mechanism for accessing & storing the data in the database.
The ‘domain-specific objects‘ reference is key here and are defined as:
Domain objects are represented by entities and value objects that exist within a domain layer. These objects contribute to a common model and are exposed as a data service, which is also provided by the entity framework.
The entity framework is a layer of abstraction that sits on top of the underlying relational database (SQL Server). This abstraction allows developers to work within a standard framework. Yes, you could run SQL queries on the underlying database directly, but this gets really ugly and isn’t supported.
LINQ is Microsoft’s .NET Language-Integrated Query (language).
What is also important to note is that entities follow some form of continuity and identity (i.e. they must all have certain attributes, such as an ID field or callable methods). This standard allows for a consistent interaction with the domain objects.
In the case of vRA, all domain-level objects (entities) are provided under the ‘ManagementModelEntities.svc‘ data service model. Within this data service model, entities are organised into their own ‘tables’, known as ‘Entity Sets’, and entities can also link to (relate to) other entities. Getting an understanding of the entities will make your life as a vRA/vRO developer so much easier. Continue reading