2.8 Deployment Diagrams

The final UML diagram type (for our purposes) is the deployment diagram. Deployment diagrams are used to show how individual components are distributed across multiple systems, and how those components interact. Servers are represented as three-dimensional boxes, and individual components are represented as rectangles with two smaller rectangles attached to the left side.

There are a few key types of associations possible within deployment diagrams. For example, lines between servers specify how components installed on each server communicate with each other.

Components can be connected via solid arrows to indicate persistent relationships. In Figure 2-18, the Swing Application and the Client Façade are joined at compile time. Dashed arrows indicate runtime connections such as those between the Client Façade and an EJB Session Bean, and between the session bean and a set of entity beans.

Figure 2-18. Deployment diagram

The entity bean in the diagram is shown in the stacked style to indicate that the system contains more than one instance of it.