As discussed in previous chapters, Java EE is divided into three well-known tiers—the presentation tier, the business tier, and the integration tier. These tiers work together to promote solutions with a high level of decoupling.
In a business environment, software development is very difficult as we need to think about the whole ecosystem of the enterprise. An ecosystem includes its data source, software, data politics, security, and devices. Consequently, the developer needs to think about how to read and write data in these data sources, how the software communicates between with each other, how the data policies are implemented on the systems, how the security works on the business environment, and so on. In this case, it would be beneficial to create a tier to resolve all integration and communication problems, because their solutions will be decoupled from business logic. This is the thought process that gave birth to the integration tier...