The processing of a user request in AS Java, as outlined in the following figure involves different processes on all three layers (presentation, application, and database layer).
A web browser is the standard user interface for AS Java. A user request for AS Java is usually an HTTP(S) request that is received by the ICM. The ICM process forwards the processing requests to one of the server processes of its application server.
The actual processing takes place in the server process, whereby the user who sent the request is usually assigned the same server process again for the next request.
The server processes of AS Java are also called nodes. All processes of AS Java, together with the database schema, form the Java cluster. In contrast to the work processes of the AS ABAP, the server processes of the AS Java are multi-threaded. This means that a server process consists of many threads, and one request can be processed in each thread. One server process can therefore process many user requests in parallel.
To process user requests, it is often necessary to read data from the Java schema of the database or to write to it. To do so, each server process is connected multiple times to the Java schema of the database via a connection pool (DB pool).
Once processing is complete, the processing result from the server processes is returned to the web browser via the ICM.
The buffers help to speed up the processing of user requests. This means that the data does not have to be read from the database every time it is needed, but can be called very quickly from the buffer. Each server process has its own buffer.
The server processes are split into different functional modules called managers and services. The managers form the Java Enterprise Runtime. The Java Enterprise Runtime provides basic core functions of AS Java. Alternatively known as a kernel.
Together with the interfaces and libraries, the services are called Java EE Engine Components. The Java EE Engine Components provide programming interfaces (APIs) to the applications; the applications can then use these APIs to access the AS Java functions.
In the case of an HTTP request, the ICM process uses a Java EE handler to forward the request to a server process of this application server.
The cluster manager of the server process receives the request and forwards it to the HTTP provider service. In the web container service, the presentation logic of the application is then processed. The web container service provides the processing of servlets and JavaServer Pages (JSP). The business structure logic of the application is processed in the form of EJB beans in the EJB Container Service. If, in the processing of the request, data from the database is required, the JDBC Connector Service is used to establish a connection to the database, and the data is requested there. If the same table content has already been queried by this server process, the content of the table buffer can be queried at the application level (if buffering is permitted for the table).
The response to the web browser using HTTP is then returned in the same way.
