For this week’s blog post, I have found an article about encapsulation. Encapsulation is more than defining accessor and mutator methods. It also follows two main objectives hiding complexity and hiding the sources of change. To understand more about encapsulation, we will first need to understand the two concepts of modularity and abstraction. In the article, Edwin Dalorzo, the author of the article, uses the example of a car to understand abstraction. He says on this, “A car is complex in its internal working. They have several subsystems, like the transmission system, the break system, the fuel system, etc. However, we have simplified its abstraction, … we know that all cars have a steering wheel through which we control direction, they have a pedal that when we press it we accelerate the car and control speed, … These features constitute the public interface of the car abstraction” (Edwin Dalorzo). This is a great example because we can use abstraction to simplify unnecessary parts that the users would not need to understand. This concept is similar to modularity. In his book Code Complete, Steve McConnell said on complexity “ the interface should reveal as little possible about its inner workings”. So now that we understand the two concepts, the idea of encapsulation starts to unravel.

One of the things that we want to always encapsulate in Java is the state of a class. This should only be accessed through its public interface. Edwin says on encapsulation in Java, “In a object-oriented programming language like Java, we achieve encapsulation by hiding details using the accessibility modifiers … With these levels of accessibility we control the level of encapsulation, the less restrictive the level, the more expensive change is when it happens and the more coupled the class is with other dependent classes (i.e. user classes, subclasses, etc.).” (Edwin Dalorzo).  It is crucial that we keep this idea in mind while we design encapsulation for these public interfaces so that we can foster evolution of our APIs.

As talked about in the article, it is often wondered why we need to use accessor and mutator methods in Java, aka getters and setters. With encapsulation in mind, it is not there to hide the data itself but the implementation details on how the data is being manipulated. So once again we would need a public interface to gain access to this data. However, by exposing this data we risk losing encapsulation. So this is why we would need to encapsulate this information.

https://dzone.com/articles/why-encapsulation-matters

From the blog CS@worcester – Michale Friedrich by mikefriedrich1 and used with permission of the author. All other rights reserved by the author.

In this final week of blogging for CS-343, I wanted to look over the General Responsibility Assignment Software Principles, or GRASP.

I took to learning about GRASP from Code Specialist at https://code-specialist.com/code-principles/grasp/, which discussed all nine GRASP principles and provided diagrams and code examples.

I’ve learned that the nine principles are: controller, creator, indirection, information expert, low coupling, high cohesion, polymorphism, protected variations, and pure fabrication.

Controller: helps “control” (not implement) events indirectly related to the user interface. It acts as a mediator between signals from the user interface and the backend.

Creator: a class responsible for the creation of certain objects, such as object A. This principle has a few rules for the creator, which are: creator B aggregates instances of A, B contains A objects, B records instances of A objects, B closely uses A objects, and B has the inputs for when A is created.

Indirection: is an idea that works with other concepts, like low coupling. It serves to avoid direct coupling. For example, the controller is an indirection between the UI and backend.

Information expert: a class containing the information needed to decide where an operation should occur. The operation should occur where most of the input needed for it is stored.

Low coupling: the idea of little interdependency between modules. By having few dependencies between modules, it would be less complicated to make changes to the code.

High Cohesion: describes the flow inside modules, not between them. High cohesion mainly helps to reduce complexity. Classes should be made to only fit their purposes and not go beyond that scope. We should not have large classes that do not really relate and are hard to work with.

Polymorphism: there are many variations of the same method and they work differently in different classes.

Protected variations: wrap unstable code with a stable environment. The unstable code can be wrapped with an interface that creates multiple implementations of that code.

Pure fabrication: creating a class that does not represent a real-world problem, but serves to support low coupling and high cohesion.

I thought this was a nice source to learn from because the page has neat orientation and provides diagrams and some sample code. Many of these principles seem interconnected with other principles to help reduce the complexity of code. High cohesion reminded me of the SOLID design principle single-responsibility principle in which classes have one responsibility and should not cover more than that responsibility. It would make the classes easier to understand, and less changes would need to be made to the class if it covers less functions. All of these principles I have learned will help me write neater code in the future as I keep in mind the need to reduce interdependence and complexity.

From the blog CS@Worcester – CS With Sarah by Sarah T and used with permission of the author. All other rights reserved by the author.

I wanted to focus my last blog post on frontend development because I think I have a better understanding of the backend than the frontend, and while I think I get how the frontend works and what is going on in it, I was having trouble in the latest activity adding to the frontend that we were given and connecting it to the backend. I also had to make some edits to my assignment and could talk about what I had trouble with.

First, with the last homework assignment, I had a few issues with adding onto my frontend. When I made the new filterByName button, I did not add it to the data() section, which would cause an error. I added the button and the status I used for it to the data() section and gave them default values similar to what was already there. My other two issues had to do with my filterNames method, where I was stating the endpoint to get names incorrectly, and I had the resulting response given to the wrong variable. I was a little stuck at first changing my endpoint name because at first I changed it to just /items instead of items/{name}, which I had before and is not the correct way to get to the endpoint. I was trying to add a name variable to the get method as a way of getting the names, but after looking through the frontend example, specifically versions v2 and v3, I saw that I could just connect to the names of the items endpoint with /items + itemName. The last issue was sending the response to the wrong variable because I had it set to just a names variable, but I changed it to a filter variable to show that the result is being given to the resulting filter, not changing the actual names in the endpoint.

I also did some more into endpoints to see if there was anything I was missing when it came to understanding the frontend. I read an article called “What is Front-End Web Development?’ by Trio Developers, and most of the article was a review of what I knew from the previous article I read for the blog: The frontend makes up the interface of the program that users interact with, and the frontend uses different elements that can be interacted with to go through the site, such as drop down menus and sliders. The frontend is immersive for the user interacting with the site.

The article goes on to talk about what frontend developers do, and their jobs focus on developing interfaces for code, improve upon applications, and work on UI/UX designs and their usability/feasibility. It also goes into the differences between the frontend and backend, but I already talked about those in the previous blog post.

I think I correctly fixed my mistakes on my homework assignment, and while the information from the article was mostly review, it was still a good read and I liked how it talked more about developers and what their jobs are.

https://trio.dev/blog/front-end-web-development

From the blog Jeffery Neal's Blog by jneal44 and used with permission of the author. All other rights reserved by the author.

https://www.dossier-andreas.net/software_architecture/pipe_and_filter.html

The Pipe-And-Filter architecture is conceptually very simple. It essentially consists of breaking down one operation into a sequence of smaller operations, in which the input of each is the output of the previous. These operations are called “filters” and the connectors linking them are called “pipes”. Sometimes the terms “pump” and “sink” are used to refer to the initial input and final output, respectively. I think making up those last two terms is a little excessive, but overall I like the metaphor – it makes me think of an actual physical machine, which is similar to how I prefer to think about computing in general.

The most well-known example of this pattern is seen in Unix and Unix-like operating systems, which are also the most obvious example of this pattern’s utility. There is no need for any program to have word counting functionality, because its output can be piped into wc, a program that only does that. Similar functionality for pattern matching is provided by grep. With this ecosystem of programs in place, a skilled user of a Unix shell has a great deal of functionality available to them through composing these programs in different ways, as opposed to creating new programs from scratch that do slightly different things than what the programs on their machine already do. Another common example is compilers, which also function in a similar way in order to streamline and simplify the process of translating between languages. The OpenGL rendering pipeline has similar motivations, only for processing graphics instead of programs.

One drawback of a pipe-and-filter system is that it has the potential to draw too much overhead. Being able to pipe something into wc rather than counting words yourself is a more flexible solution, but it does involve running a separate program. At small scales (i.e. most use cases) this isn’t an issue, but if your data is large enough you may need to abandon this system.

Before looking into this, I wasn’t really aware of the pipe-and-filter architecture as a distinct pattern. I was aware of how the Unix ecosystem worked, but I thought the practice of piping together small programs in sophisticated ways was just a quirk of that operating system. I didn’t connect the dots that it was also the same basic concept being used in graphics pipelines, even though I was aware of them. I also have always regarded compilers as a little magical, and seeing that their workflow can be decomposed like this makes them seem a little more approachable.

From the blog CS@Worcester – Tom's Blog by Thomas Clifford and used with permission of the author. All other rights reserved by the author.

My experience with HTML programming outside of classwork pretty much begins and ends with making forum posts look fancy in 2012 messaging boards, and I have even less experience designing frontends with HTML. I wanted to use this blog post to learn more about how to build frontends. Matias Lorenzo’s “Frontend Architecture and Best Practices for Consuming APIs” seemed like a very good start.

Lorenzo notes that issues begin to arise when designing a frontend because that frontend is often dependent on a backend API. This means that whenever the backend or the API undergoes a change, the frontend must also be changed. Lorenzo describes some other issues one might encounter when integrating an API into their frontend. APIs may use lengthy key names that necessitate mass replacement. APIs might structure data in a way that is difficult to fully utilize, or they might include too much data.

Lorenzo proposes a frontend architecture that would further isolate the frontend from the backends it depends on so that it is more stable when the backend changes and is titled model-controller-serializer. Below is a diagram of how this architecture fetches information, in this example it is fetching products for a storefront, from an API:

Controllers in this architecture are the point of contact between the rest of the app and the API. This portion of the app should be able to create any relevant request. Information comes in through the controller, is deserialized by the serializer, then is passed to the model to create instances of that information.

Serializers in this architecture decipher information coming in from the API. If an API includes information that is not relevant to the app, the serializer can remove this information. The serializer can also change the type of a field (eg. from a string to a boolean). Similarly, if the API uses long or clunky names for fields, the serializer can alter the name of the field before passing it along.

Models in this architecture are representations of information from the API that can be read by the app. These store information as an object in Javascript (or whatever language is being used in the app) so that it is easy to access and understand.

I chose this source because I wanted a more in-depth look at frontends. I know what a frontend does, but I would be at a loss for how to design one. This frontend architecture Lorenzo describes seems really useful to help keep the frontend and backend seperate, and I will be keeping this reference in mind for future projects.

From the blog CS@Worcester – Ciampa's Computer Science Blog by robiciampa and used with permission of the author. All other rights reserved by the author.

Christian Shadis

As I transition into the final semester of my undergraduate degree, I plan to learn Javascript. In my Software Construction, Design, and Architecture class, we briefly explored and edited some frontend code in Node.js and Vue.js. Using my prior knowledge in Java, I was able to understand how most of the code was functioning. As Javascript continues to rise in popularity, it would be a valuable language to add to my skillset. One of the fundamental aspects of learning Javascript, or so it seems, is to understand the Document Object Model (DOM). Having used his book HTML & CSS: Design and Build Web Sites to supplement my knowledge in web design, I decided to consult the fifth chapter of Jon Duckett’s Javascript and JQuery: Interactive Front-End Web Development to learn more about the DOM.

Duckett first specifies the DOM as a set of rules, separate from the HTML and CSS of the website, which “specifies how browsers should create a model of an HTML page and how JavaScript can access and update the contents of a web page while it is in the browser window” (Duckett 184). In other words, the DOM acts analogously to an API in that it facilitates or enables real-time communication between JavaScript code and the HTML page. Duckett proceeds to describe the DOM tree, the benefits of caching DOM queries, and how to traverse the DOM tree. He also described how to access, update, add, and delete HTML content from the page using the DOM. The chapter included a bit of bonus information such as cross-site scripting attack prevention and how to view the DOM in each of the major web browsers.

Reading this chapter was useful in contextualizing how the different parts of a webpage interact with each other. In addition to learning the fundamentals of the DOM, I also gained experience reading JavaScript code, which is a great way to learn how a language works. What stood out to me most about the material was the parallels between the DOM nodes and the LinkedList data structure. Having coded an implementation of the data structure in a previous course, it was intuitive to see how traversal of the DOM tree worked.

I plan to continue to learn JavaScript, and plan to read the remainder of the book. Web design is becoming more ubiquitous by the day, and thus a more valuable tool for developers to have. I would highly recommend this book and others by Jon Duckett to developers – the design is pleasing, he provides sample code, and offers excellent simplistic explanations.

Duckett, J. (2014). Document Object Model. In JavaScript & JQuery: Interactive Front-end web development (pp. 183–242). essay, John Wiley & Sons.

From the blog CS@Worcester – Christian Shadis' Blog by ctshadis and used with permission of the author. All other rights reserved by the author.