Online businesses often look for ways to accept digital payments quickly, securely, and easily. These requirements don’t often come in a one-size-fits-all solution. Because of this, e-commerces relies on more than one platform to perform their services. We understand that dealing with multiple customers and merchants can get complicated. This can jeopardize business growth if you aren’t very careful.

Payment gateways have become the standard for e-commerces, marketplaces or web-based service platforms. Why? They allow businesses to integrate more than one Payment Service Provider (PSP). What do they also do? They’re responsible for authenticating and triggering the actual transaction. 

When creating payment gateways, developers should put a lot of thought into what design pattern to use and when to use them. In this post, we’ll explore what Java design patterns are. We’re not talking about every single pattern though. We want to focus on API gateway patterns, which are ideal for creating payment gateways. 

What’s a Java Design Pattern?

Design patterns are coding solutions, in Java, that have been proven to work. They provide an industry-standard approach to solve a recurring problem. Java developers find it handy to recur to a design pattern. This leads to a more robust code and faster implementation. Design patterns are already defined. Therefore, it is easier to understand what the developer is creating. If you’re a new member of a team, you’ll find this particularly useful!

Professional software developers recommend using design patterns, also known as Gang of Four design patterns, for several reasons: 

  • First, they provide solutions that help define the system architecture. 
  • These well-proved solutions provide transparency to the design of an application. 
  • Patterns can be reused in many projects. 
  • They provide clarity to the system architecture and help build a better system. 

The Gang of Four divides the 23 existing design patterns into three categories. These categories are: creational, structural and behavioural design. Creational patterns provide ways to instantiate or call a class of single objects or groups of related objects. This category includes five patterns, among them are prototype or builder patterns. Structural patterns provide ways to define relationships between classes or objects. A couple of examples of structural patterns are composite, decorator or bridge patterns. Finally, behavioural patterns define ways in which classes and objects communicate. 

Introducing the API Gateway Pattern

Software often interacts with other systems. Such interaction can be as libraries, remote calls to external services or with specific files or databases. In some cases, a system may use (or may connect to) some form of API that produces mismatching results. Whenever this occurs, developer Martin Fowler recommends implementing a gateway. He defines it as “a piece of code within our system that interacts with the interface of the gateway, which is designed to work in the terms that our system uses.” 

To create a gateway, developers first need to understand what the code needs to do. How should it interact with the external system? How many systems are there? The gateway first translates the system’s function calls into requirements a foreign API can read. The system then receives the results and translates them back into consumable code. 

Fowler insists that gateways should only focus on translating domestic and foreign concepts. This is bettemoreing additional actions. He does suggest adding a connection object (that is, a session between a Java application and a database) to the gateway’s simple structure. The gateway is able to translate its parameters into a foreign signature. Once translated, it can call the connection using that same signature. 

In the original Gang of Four Patterns, quoted in the previous section, there is no mention to payment gateways. This pattern takes elements from both Facade and Adapter patterns. However, in an Adapter pattern, both interfaces are already present. In the gateway’s pattern, the system’s interface is being defined as it interacts with the foreign element. To Fowler, this makes it a different pattern altogether. 

When to use an API gateway pattern?

A gateway pattern is recommended whenever a system needs to access external software and connecting to this external element is difficult. Such is the case of a payment gateway, which connects multiple key players, from merchants and banks, to a payment platform. 

An API gateway pattern is useful whenever a system requires access to remote services. Because the gateway removes the need for a slow remote call, developers also recommend using it for external systems. Another virtue of a gateway is its ability to swap out one external system for another. The system can switch to a new external system without having to adjust the code for every interaction with a new system.

One of the key purposes of a gateway is to act as a translator for foreign vocabulary that will complicate the main or host code. This sounds like a trivial decision, right? It isn’t! Using foreign vocabulary on a project’s own source code can mean an uncalled effort. As Fowler puts it, instead of wrapping a language’s collection classes, it is easier to accept this new vocabulary as part of the system itself. 

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