Chapter 1. The world of open source ESBs
Figure 1.1. The point-to-point model describes an environment where applications are integrated with a unique and custom-made integration solution.
Figure 1.2. An application landscape using an ESB to integrate the applications
Figure 1.3. Here’s a typical example of an application with a three-tier architecture. The application logic is divided into three layers, which can be distributed over multiple physical servers to improve scalability and performance if necessary.
Figure 1.4. Here’s an example where integration between multiple applications is necessary. The call center application needs a single-client view from the ERP, CRM, and COBOL applications.
Figure 1.5. The architecture shown in figure 1.3 is extended with an integration layer that provides the logic needed to integrate with other applications.
Figure 1.6. Here we introduce an ESB to the call center architecture. The ESB provides functionality to communicate with the three back-end applications and to route the message to the right backend application.
Figure 1.7. The ESB can use several options to configure and store the location of the CRM client information service. A common option is an XML file configuration, but there are alternatives, such as a database or a service registry.