We have gone through five chapters already in this book, but we have yet to cover a topic that has to do with one of the main purposes of a CMS—data storage. Okay, we hinted at it in the previous chapter and also saw an example of a configuration object in the second one. However, we merely scratched the surface of what is possible. It's now time to go ahead and dive into everything related to how you can store data in Drupal 8.

In this and the next chapter, we will talk about a lot of things related to storage and data manipulation, and take a look at a lot of examples in the process. The focus of this chapter will, however, be more theoretical. There is a lot of ground to cover, as there are many APIs and concepts that you will need to understand. However, we will still see plenty of code examples to demonstrate in practice what we are talking about. In the next chapter, though, to make up for it, we will almost entirely work with code and build a few functionalities.

More concretely, however, this chapter will be divided into three main logical parts (not necessarily represented by headings).

First, we will talk about your options for data storage. We will talk about the State system with its key/value store, tempstore, user data, configuration, and finally, entities—the big one. We will leave the cache out of this, because it will be covered in a separate chapter. We will see examples of all these options and go into the architectural details necessary to understand how they work.

Second, we will dive deep into the Drupal 8 Entity API to understand the architecture behind it—how data is stored and, more importantly, modeled. I am referring to the TypedData system here.

Finally, we will look at how we can manipulate entities; in other words, how we can work with them and extract data—basically, the day-to-day working with entities. One of the main topics here will be, of course, querying and loading entities. Moreover, we will also cover the validation aspect of this process.

By the end of this chapter, you should be able to understand a great deal about storage in Drupal 8 and make decisions on which options to choose for your requirements. You'll know the differences and the reasons for using one over another. Moreover, you'll get a good understanding of the Entity API, which, in turn, will allow you to more easily navigate through Drupal code and integrate with the entity system. Lastly, and probably, the most common thing Drupal developers do, you'll be able to work with entities: perform CRUD operations, read and write field values, and more of this good stuff.

So, let's begin.