AS Java System Architecture

The AS Java system consists of three logical layers:

...

● Java Enterprise Runtime – comprises low-level subsystems that provide functions such as classloading, cluster communication, persistent configuration data management, and so on.

● AS Java System Components – consists of facades, interfaces, libraries and services components that provide various runtime functions and programming APIs.

● Applications – refers to the applications that are deployed and run on the AS Java.

Features

The AS Java system architecture is based on the following general rule: components from a higher level can use components from a lower level only through a set of defined APIs – facades; whereas components from a lower level are not aware of the APIs of the components from a higher level and therefore cannot use them.

This rule is reflected by the order of starting the system modules: the runtime is started first, then the services (the libraries are loaded, the interfaces resolved at this phase), and the applications are started last. The system is considered as started when all runtime managers and core services components are started properly.

The AS Java system components use the Framework APIs to connect to the Java enterprise runtime. Applications use the AS Java system components using the APIs that are defined by Java EE 5 specification (and supporting specifications) and SAP-proprietary APIs.