How AEM Works!

Adobe Experience Manager (AEM) is massive. There’s a lot of confusion when most developers and content editors come to this proprietary content management system. There are new terminology, processes and tools that one must understand. It can be overwhelming. Though it is impossible to write everything about AEM architecture in a single post, I wanted to write a post detailing some fundamentals for developers, but could still be read by anyone already working in AEM (using a language everyone can understand). So this is not a deep dive type of post. Understanding how AEM works will help you as a developer or author have a better insight into issues you may be having. My aim in the post is to give you the BIG picture. This is AEM architecture fundamentals.

AEM is a cloud based client-server system for building enterprise grade websites and applications. A copy of AEM running on a server is what you would normally hear of being referred to as an instance. The installation of AEM usually involve two instances running on separate machines on a production site. These is the author and the publish instances. Most of you know what the author instance is. This where you edit content. By editing content, i mean this is where you create, upload and management content on your website. Pretty much any website administration is done on the author instance (the name make sense since you are actually authoring content). Typically a content editor logs into AEM, edits or creates a page and either put their work in some kind of workflow for it to be approved, or perhaps they just publish the page when that content is ready (which goes live right away). What happens in the background, most of us don’t know. Here is where i want to shed a little light on because i feel knowing it gives you better insight into issues that might come up. Read More

Circular Linked List

In the previous post on singly and doubly linked lists, recall that the collections last nodes next pointers were always NULL. This is because they had nothing to point to. But what if this is not what we wanted? What if when we get to the last node, we wanted to point the next pointer back to the head node, like a photo gallery application (when we get to the last picture, the next picture should be the first). This is where circular linked lists come from (they allow us to rotate through our collection). This means that circular linked lists have no end. One must be careful if they are going to iterate through the collection, or you could end up in an infinite loop.

So in a circular linked list, there are no nodes with a NULL pointer. For eg, in a case where there is only one node (the head node), the next pointer points back to the itself. Remember in previous posts that i said when a collection is empty and you add a new node, their next and previous pointers are NULL? Well in this type of linked list, they point back to itself, well until we change its pointers.

What about the previous node of the head? Remember it was NULL in previous posts? There is another type of linked list called doubly circular linked list (i know, the names are getting ridiculous). In a doubly circular linked list, the previous pointer of the head points to the tail node. Lets look at a diagram. Read More

Doubly Linked List

In the previous post, we talked about what data structures are. We learned that a linked list is a type of data structure, and we learned why they were important. We particularly looked at singly linked lists as a type of linked list, and we saw some of its usage and operations. Even though singly linked lists have their use in the real world, chances are you will find doubly linked lists easier to implement, more practical and have more real world use. One issue you might have noticed with singly linked lists is that it only has a reference to the next node (or next pointer). This makes it harder to find what the previous node is. We had to write some pretty length code just to find the previous node. The doubly linked list is a type of linked list that has a next and previous properties on the node (pointers), making it very easy to enumerate the node collections in any direction (forwards or backwards). This means we can navigate in both directions. Let us start from the top. Imagine you have a node collection with one node ( like we did from the previous post) Read More