Hello, again my friendly neighboorhood readers!

This week I have been again been reading up on those crazy Antipatterns I discovered week. As you can probably tell by the title, the Antipattern I am writing about this week is a Halloween themed Antipattern. I know it’s a little late but today’s Antipattern is the Poltergeist.

A Poltergeist is a class that has a limited role to play or limited responsibilities in a system. This practice adds unnecessary abstraction and their short life cycle means more wasted resources. Poltergeists normally appear to initiate some other action of a class that has a more permanent status. A Poltergeist is easily identifiable as they will typically bear the “_manager” or “_controller” title in their name. The main three disastrous effects of the Poltergeist Antipattern is a waste of resources every time they are called, they utilize redundant navigation paths, and the clutter the object model, getting in the way of proper object-oriented design. If a Poltergeist Antipattern is left alone it can result in such occurrences as transient associations, stateless classes, redundant navigation paths, short duration, temporary classes, and objects, and single operation classes. Some typical causes that lead to a Poltergeist Antipattern manifesting are a lack of object-oriented architecture, using the incorrect tool for the job, and of course, a specific disaster such as management incompetence.

Now how do we fix this Poltergeist problem? Well, they gotta go. Of course, once the Poltergeists are gone, the functionality they had must be replaced with an adjustment to the architecture. Another solution is to utilize the 80% solution that we discussed in the post discussing the Blob Antipattern.

Now, I do not know about you reader, but I believe that this is definitely an Antipattern that every programmer falls prey too, especially when they are beginning. I can think of many programs that I have many over the years that have had at least one Poltergeist stalking around in them. This does make me rethink how I will program in the future. While the programs I may write now do not need any real optimization, in the future, optimization is going to be a required skill for me.

Well, that is it for today readers. Have a good week until next time!

From the blog CS@Worcester – Computer Science Discovery at WSU by mesitecsblog and used with permission of the author. All other rights reserved by the author.

We learned about Model-View-Controller in class but there are more software architecture patterns, there are different layer is useful for different design. This blog is based on the book Software Architecture Patterns, by Mark Richards, Boston-based software architect who’s been more than 30 years about how data should flow through software. The author made top 5 software architecture patterns, which show how to choose them.

Layered (n-tier) architecture, this architecture arranged so the data enters the top layer and works its way down each layer until it reaches the bottom, which is usually a database. This is where the Model-View-Controller (MVC) structure, as we know, is the standard software development approach offered by most of the popular web frameworks, is clearly a layered architecture. Best use for: New applications that need to be built quickly, enterprise or business applications that need to mirror traditional IT departments and processes and applications requiring strict maintainability and testability standards.

Event-driven architecture helps manage this by building a central unit that accepts all data and then delegates it to the separate modules that handle the type. This architecture is easily adaptable to complex, often chaotic environments, scale easily and easily extendable when new event types appear. This type of architecture best for asynchronous systems with asynchronous data flow, applications where the individual data blocks interact with only a few of the many modules.

Microkernel architecture, the basic routines for displaying a file and editing it are part of the microkernel. The solution is to push some basic tasks—like asking for a name or checking on payment—into the microkernel. Good use for this architecture is the applications with a clear division between basic routines and higher order rules and the applications with a fixed set of core routines and a dynamic set of rules that must be updated frequently.

Microservices architecture, the goal is to create a number of different tiny programs and then create a new little program every time someone wants to add a new feature. It’s used mainly when the different tasks are easily separated. In many cases, different tasks can require different amounts of processing and may vary in use. Best use for this is websites with small components, rapidly developing new businesses and web applications.

This is interesting architecture layers type, it is important to know and compare to real life application. I hope we more type to know more about the architecture, specially about website.

Link

From the blog CS@Worcester – Nhat's Blog by Nhat Truong Le and used with permission of the author. All other rights reserved by the author.

For my final blog for “Software Design and Architecture” this semester, I decided to research time management for doing software projects. This is an issue that I ran into creating my final project, and I thought it would be worthwhile to learn from my experience while it was fresh in my mind.

I thought this would be particularly helpful because I would like to do a few projects for fun over the winter break. I don’t think that I’m alone in that without a looming deadline, what little time management skills I have tend to go out the window. I hope this will change this time. I doubt reading an article will transform me into an extremely productive person, but at least it might point me in the right direction. I can only hope.

The article that I found was from *codeproject.com* and was titled “Time Management Tips for Developers.” I thought it gave some good pieces of advice. Even if you are not a software developer, you could benefit from all the advice given. I will focus on three pieces of advice that I would like to work on.

“Set your goals: long term and short term”: This is something that I know I should be doing, but I never do it in a methodical way. I make myself a goal, but never stick to it. I also never write it down, either. It is an incredibly lazy process. Which, funny enough is the next point.

“Do not plan in a lazy way”: Guilty as charged. I don’t put very much effort into planning. It’s no wonder I don’t stick to it. However, I have found it is sometimes hard to plan a project that I have never done anything quite like. Strangely enough, this thought was the topic of the next point.

“If you can’t plan, just track”: You should keep track of what you are able to get accomplished in a day and note where you waste your time. This seems like something incredibly useful for accurately gauging how your time is spent. It is too easy to either get discouraged or have false enthusiasm because you have either under- or overestimated how productive you were.

It seems like the author has some experience in doing projects like I am doing. It is really impressive that he can follow my thought process when reading one point and have the next point agree with what I was thinking in the next point. There were several other points that were good as well. I highly recommend checking it out.

Work Cited:

https://www.codeproject.com/Articles/11502/%2FArticles%2F11502%2FTime-Management-Tips-for-Developers

From the blog Sam Bryan by and used with permission of the author. All other rights reserved by the author.

In our last week of blogging, (I know it’s sad) I decided that I will be continuing on a topic that was previously discussed a while back. (Two weeks because I procrastinated, but it’s okay we won’t talk about that). Today, or tonight rather, we will be discussing cyber security. I did my normal routine, and went back to my favorite website which I will post at the end of my last blog post for those who are interested. Anyways, the article is titled Proactive Approach to Defending Computer Systems. I saw the word proactive, and I jumped right into the article.

The article is about how three different research teams (U.S. Army Research Laboratory, the University of Canterbury in New Zealand and the Gwangju Institute of Science and Technology in the Republic of Korea) came together to take a step in the right direction in the field of cyber security. According to scientists, which who are not mentioned for some odd reason, this is a demanding research topic.

The article then talks about the threat of cyber attacks like most articles that talk about cyber security do. In fact, the beginning of this article is more or less just an introduction on cyber attacks and how they work, but we won’t discuss this because we all know what cyber attacks involve, or at least I think we do, and this is my blog so I’m moving on.

The real information comes in about halfway through the article. A new method was found, and it is known as Moving Target Defense, or MTD.

“The concept of MTD has been introduced with the aim of increasing the adversary’s confusion or uncertainty by dynamically changing the attack surface, which consists of the reachable and exploitable vulnerabilities,” Cho said. “MTD can lead to making the adversary’s intelligence gained from previous monitoring no longer useful and accordingly results in poor attack decisions.” (Disclaimer: this quote was in the article, and I didn’t want to take credit for a direct quote). This explains the concept of MTD and the rest of the article talks about how it is used to prevent information from being taken by attackers. To summarize, use a bunch of fake changing IP addresses to prevent the attack.

I didn’t enjoy this article as much as I thought I was going to, but I do like the concept of it is hard to hit a moving target, so lets keep changing the fake IP address so hackers can’t do anything. I think that this is definitely a huge advancement in terms of cyber security, and hopefully it can prevent a lot of attacks. If i had to change one thing about the article, it would be the half page introduction on cyber security, but I don’t write articles so they can do whatever they want.

From the blog CS@Worcester – My Life in Comp Sci by Tyler Rego and used with permission of the author. All other rights reserved by the author.

The Adapter pattern is easy to understand as the real world is full of adapters. The general idea of an adapter in software development is identical to the one in the physical world. If you have been to different countries, you probably recognized that a lot of them are using differently shaped power sockets. Quite often, they are shaped in a way that the plug of your electrical device doesn’t fit. So, how do you connect the charger of your mobile phone or laptop to these power sockets?

The answer is simple. You get an adapter which you can put into the power socket and then you put your plug into the other end of the adapter. The adapter changes the form of your plug so that you can use it with the power socket. In that example and in most other situations, the adapter doesn’t provide any additional functionality. It just enables you to connect your plug to the power socket. The Adapter Pattern applies the same idea to object-oriented programming by introducing an additional adapter class between an interface and an existing class. The adapter class implements the expected interface and keeps a reference to an object of the class you want to reuse. The methods defined by the interface call one or more methods on the referenced object and return a value of the expected type. By doing that, the adapter class fulfills the expected contract by implementing the interface and enables you to reuse existing, incompatible implementations.

The Adapter Pattern is an often-used pattern in object-oriented programming languages. Similar to adapters in the physical world, you implement a class that bridges the gap between an expected interface and an existing class. That enables you to reuse an existing class that doesn’t implement a required interface and to use the functionality of multiple classes, that would otherwise be incompatible.

One advantage of the Adapter Pattern is that you don’t need to change the existing class or interface. By introducing a new class, which acts as an adapter between the interface and the class, you avoid any changes to the existing code. That limits the scope of your changes to your software component and avoids any changes and side-effects in other components or applications.

Thank you for reading!

Reference

https://dzone.com/articles/adapter-design-pattern-in-java

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

The Singleton pattern encapsulates a shared resource within a single unique class instance. This instance arbitrates access to the resource and storage-related state information. A class method provides the reference to this instance, so there is no need to pass the reference around Any object that has access to the Singleton’s class header can use the Singleton.

This design pattern defines the structure of a class that can have only one instance. A Singleton encapsulates a unique resource and makes it readily available throughout the application. The resource might be hardware, a network service, a persistent store, or anything else that can be modeled as a unique object or service. Singletons may often be modeled as a server within the application that accepts requests to send, store, or retrieve data and configure the resource state.

Implementation

Implementation of the Singleton pattern often typically creates a single object using the factory method, and this instance/object is called a shared instance in most cases. Since the access to the instance is passed on though a class method, the need to create an object is eliminated.

Pros and Cons

Singletons are not the answer to every problem. Like any tool, they can be short in supply or can be overused. Some developers are critical of Singletons for various reasons. We will examine this critique and discuss ways to address them briefly. The criticisms, for the most part, fall into two categories:

Singletons hinder unit testing: A Singleton might cause issues for writing testable code if the object and the methods associated with it are so tightly coupled that it becomes impossible to test without writing a fully-functional class dedicated to the Singleton.

Singletons create hidden dependencies: As the Singleton is readily available throughout the code base, it can be overused. Moreover, since its reference is not completely transparent while passing to different methods, it becomes difficult to track.

To avoid these complications, when considering the Singleton pattern, you should make certain that the class is a Singleton. Also, while thinking of designing the Singleton design pattern, keep testing in mind and use dependency injection whenever possible, which means: try to pass the singleton as a parameter to the initializer whenever possible.

Thank you for reading, please share it if you found it useful!

Reference

https://www.geeksforgeeks.org/singleton-design-pattern-introduction/

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

Motivation:

Sometimes we need the ability to control the access to an object. For example, if we need to use only a few methods of some costly objects we’ll initialize those objects when we need them entirely. Until that point, we can use some light objects exposing the same interface as the heavy objects. These light objects are called proxies and they will instantiate those heavy objects when they are really need and by then we’ll use some light objects instead.

This ability to control the access to an object can be required for a variety of reasons: controlling when a costly object needs to be instantiated and initialized, giving different access rights to an object, as well as providing a sophisticated means of accessing and referencing objects running in other processes, on other machines.

Consider for example an image viewer program. An image viewer program must be able to list and display high resolution photo objects that are in a folder, but how often do someone open a folder and view all the images inside. Sometimes you will be looking for a particular photo, sometimes you will only want to see an image name. The image viewer must be able to list all photo objects, but the photo objects must not be loaded into memory until they are required to be rendered.

Intent:

The intent of this pattern is to provide a placeholder for an object to control references to it.

Implementation:

The participants classes in the proxy pattern are:

Subject – Interface implemented by the realSubject and representing its services. The interface must be implemented by the proxy as well so that the proxy can be used in any location where the RealSubject can be used.

Proxy – Maintains a reference that allows the Proxy to access the RealSubject. Implements the same interface implemented by the RealSubject so that the Proxy can be substituted for the RealSubject. Controls access to the RealSubject and may be responsible for its creation and deletion. Other responsibilities depend on the kind of proxy.

RealSubject – the real object that the proxy represents.

Applicability:

The Proxy design pattern is applicable when there is a need to control access to an Object, as well as when there is a need for a sophisticated reference to an Object. Common Situations where the proxy pattern is applicable are:

Virtual Proxies: delaying the creation and initialization of expensive objects until needed, where the objects are created on demand.

Remote Proxies: providing a local representation for an object that is in a different address space. A common example is Java RMI stub objects. The stub object acts as a proxy where invoking methods on the stub would cause the stub to communicate and invoke methods on a remote object found on a different machine.

Protection Proxies: where a proxy controls access to RealSubject methods, by giving access to some objects while denying access to others.

Smart References: providing a sophisticated access to certain objects such as tracking the number of references to an object and denying access if a certain number is reached, as well as loading an object from database into memory on demand.

Related Patterns:

Adapter design Pattern – The adapter implements a different interface to the object it adapts where a proxy implements the same interface as its subject.

Decorator design Pattern – A decorator implementation can be the same as the proxy however a decorator adds responsibilities to an object while a proxy controls access to it.

Reference

https://javapapers.com/design-patterns/proxy-design-pattern/

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

Today, in this final post of the semester for CS-343 I will be examining the JPA architecture. This is something I have been curious about after browsing articles on DZone for the past couple of weeks and seeing this topic pop up a lot, luckily they made a good introduction post this week. From the article: “The Java Persistence API is the Java standard for mapping Java objects to a relational database”, this is something that I have been wondering how to do since we started working with the REST APIs and our projects that have been using Java HashMaps for makeshift databases instead of something more permanent like SQL. This article briefly introduces and explains the functionality of the six key parts of the architecture for JPA. The article gives a diagram for these six units and the multiplicity of their relationships. The article then gives a simple example of mapping a simple Java POJO Student class into data for a database, using the student ID as the primary key. I was surprised at how easy this translation was, all it includes is a couple of tags for columns above the instance variables that designate the database column, and which one is the primary key to generate in the database. The article then creates an application class that uses the various entity classes to store a newly created student into a database. I liked the simplicity of the article as most introductory articles are on this website for what are advanced programming topics, but my biggest criticism is that this article has brief definitions for many of the elements of JPA and then links to an external site that further elaborates on them. I wished that the author put a bit more time and consolidated all of this information into one article for this site, instead of having a bunch of separate webpages on his own website. I also wish he showed in this post getting data from the database and translating it back into Java and performing manipulations on this data with methods. Overall it was a good introduction to a very useful topic and one that I would like to further look at. Going forward, I am much in favor of using this way of storing data as opposed to simple Java in-memory databases for entire applications like we did in our projects.

Source: https://dzone.com/articles/introduction-to-jpa-architecture

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