ABAP Push Channel (APC) is the ABAP framework for supporting WebSockets in ABAP engine. This framework is part of the ABAP Channles infrastructure, which is delivered with NW ABAP 740 support package 2 (SP2) for simple tests and prototyping and released with 740 support package 5 (SP5).
The basic idea of the ABAP Channels (see figure 1) is the native support of interactive and collaborative scenarios based on event-driven architecture. The scope of ABAP Channels consists of the following communication channels:
- ABAP Push channel for bi-directional communication with user agents via WebSockets in ABAP. In figure 1 the documents tagged with letter "P" mark the ABAP Push Channel communication paths.
- Publish/subscribe infrastructure for exchange of messages between either user sessions (Session C => Session A) or user session and user agents (Session C => User Agent B) residing on different servers via ABAP Messaging Channels. In figure 1 the documents tagged with letter "M" mark the ABAP Messaging Channels communication paths.
Figure 1: ABAP Channels supports eventing in ABAP
Most ABAP applications task use polling techniques to achieve an even-driven communication. For example for pushing an event from ABAP backend to a browser based user-agent, e.g. WebDynpro, Business Server Pages (BSP) or WebGUI, a pooling (in multi-seconds interval) against ICM cache is frequently used. This is a quit system resource consuming technique based on polling against a shared object area or database table, i.e. by checking the content of the shared area for the existence of an event. In SAPGUI usually the timer control is used to detect an event in the back-end. One of the the main goals of ABAP Channel technology is- whenever possible - to replace this type of inefficient eventing based on polling techniques.The ABAP channels supports the following use-cases:
- ABAP Push Channel (APC): The WebSocket integration in ABAP.
- ABAP Messaging Channel (AMC): Eventing framework for messages exchange between different ABAP sessions based on publish/subscribe channels.
- Collaboration scenario: Using APC and AMC to push messages from ABAP sessions to WebSocket clients by binding publish/subscribe channels to the WebSocket connection.
In this article we focus on the Publish/Subscribe messaging framework in ABAP called ABAP Messaging Channel.
Integration of ABAP Messaging Channel into ABAP engine