So what is a design pattern? Actually, the phrase design pattern is not associated with any programming language, and also it doesn't provide language-specific solutions to problems. A design pattern is associated with the solution to repetitive problems. For example, if any problem occurs frequently, a solution to that problem has been used effectively. Any non-reusable solution to a problem can't be considered a pattern, but the problem must occur frequently in order to have a reusable solution, and to be considered as a pattern. So a design pattern is a software engineering concept describing recurring solutions to common problems in software design. Design patterns also represent the best practices used by experienced object-oriented software developers.

When you make a design for an application, you should consider all the...

The authors Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides are often referred to as the GoF, or Gang of Four. They published a book titled Design Patterns: Elements of Reusable Object-Oriented Software, which initiated the concept of design patterns in software development.

In this chapter, you will learn what GOF patterns are and how they help solve common problems encountered in object-oriented design.

The Gang of Four (GoF) patterns are 23 classic software design patterns providing recurring solutions to common problems in software design. The patterns are defined in the book Design Patterns: Elements of Reusable Object-Oriented Software. These patterns are categorized into two main categories:

• Core Design Patterns
• J2EE Design Patterns

Furthermore, Core Design Patterns are also subdivided into three main categories of design...

Let's look at the underlying design patterns of this category and how Spring Framework adopts them to provide loose coupling between components and create and manage the lifecycle of Spring components. Creational design patterns are associated with the method of object creation. The creation logic of the object is hidden to the caller of this object.

We are all aware of how to create an object using the new keyword in Java, as follows:

     Account account = new Account(); 

But this way is not suitable for some cases, because it is a hardcoded way of creating an object. It is also not a best practice to create an object because the object might be changed according to the nature of the program. Here, the creational design pattern provides the flexibility to create an object according to the nature of the program.

Now let's look at the different...

After reading this chapter, the reader should now have a good idea about the overview of GOF creational design patterns and its best practices. I highlighted the problems that come from not using design patterns in enterprise application development, and how Spring solves these problems by using the creational design patterns and good practices in the application. In this chapter, I have mentioned only one of the Creational Design pattern categories out of the three main categories of the GOF Design Patterns. The Creational design pattern is used for the creation of object instances, and also applies constraints at the creation time in the enterprise application in a specific manner using the Factory, Abstract Factory, Builder, Prototype, and Singleton patterns. In the next chapter, we will look at the other categories of the GOF Design Patterns-the structural design pattern...