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Messages

Other versions: 7.31 | 7.40 | 7.54

Background

Messages are texts that are created using the message maintenance (Transaction SE91). They are stored in the T100 system table. In ABAP programs, the MESSAGE statement is the main element for using messages. This statement sends a message; by specifying a message type, you can define the display type and subsequent program behavior. For this reason, a distinction is made between the following message types:

  • Status message (S)
  • Information message (I)
  • Warning (W)
  • Error message (E)
  • Termination message (A)

In addition, there is a special message type, exit message (X), which causes a targeted program termination with a runtime error.

The actual system behavior after a message is sent is highly context-dependent. The current version of the ABAP keyword documentation contains a detailed list of effects caused by different message types in different contexts (such as dialog processing, background processing, during an RFC and during the processing of HTTP requests).

The originally purpose of messages is to act as dialog messages, in order to display short information (types I and S) and handle incorrect user input (types W and E), during classical dynpro processing. Messages also have aspects that overlap with exceptions:

  • The MESSAGE ... RAISING statement is a combination of the statements, MESSAGE and RAISE, which enables you to link classical exceptions with messages.
  • Using the special, predefined classical exception, error_message, you can handle error and termination messages (that occur when function modules run) in the same way as exceptions. This also applies to messages sent from the ABAP runtime environment (for example, when the automatic input check of classical dynpros is running).
  • In exception classes, you can define exception texts with a reference to messages. The message types A and X can also be used for direct program termination.

Rule

Only use messages for error handling in classic dynpros and as exception texts

Only send dialog messages during PAI processing of classical dynpros. Messages should only be used as exception texts and should no longer be used anywhere else. In particular, messages should no longer be used to force program termination.

Details

The wide use of messages for different purposes can be traced back to the previous programming model, which was only driven by classical dynpros. Here, an exception situation usually always required the direct output of a message to the user. This concept was adopted for other situations, such as targeted program terminations. Triggering a dialog message within application logic procedures violates the SoC principle and limits the usability of the relevant procedure (Method) to the context of classical dynpro processing. The predefined exception, error_message, should be regarded as a workaround that enables you to execute procedures for sending messages in the application layer or in the background.

In new programs, the use of messages should be restricted as described below.

Dialog messages

In cases where classical dynpros are still used, message types E, I, S, and W are still suitable for sending information to the user or for running error dialogs at the time of PAI (which is the original purpose of these messages types). Running error dialogs, in particular, is supported by the FIELD and CHAIN statements of the dynpro flow logic.

Exception Texts

You can use messages as exception texts and send them to the program user. This primarily involves exceptions in the presentation layer.

The MESSAGE statement allows these exception texts to be sent directly as dialog messages. A reference to a corresponding exception object can be specified directly. From a technical point of view, you must specify a reference to an object whose class includes the IF_T100_MESSAGE interface.

In addition, messages in procedures where classical exceptions are still necesary can replace real exception texts: Use the MESSAGE ... RAISING statement instead of RAISE. During this process, information on the exception text is transferred to the handler, in the system fields sy-msgid and sy-msgv1 - sy-msgv4. These fields filled using the MESSAGE statement. This works especially well for handling exceptions during an RFC, for which class-based exception handling is not possible.

Program terminations

Message types A and X cause program terminations and should no longer be used:

  • If you send a termination message of type A, the ROLLBACK WORK statement is executed implicitly. This can lead to unexpected results, if the message is handled with error_message as a classical exception (rather than causing a program termination). To be on the safe side, you should explicitly use the statements ROLLBACK WORK and LEAVE PROGRAM to exit the program.
  • If you send a message of type X, the program is terminated with the MESSAGE_ TYPE_X runtime error. Due to internal inconsistencies, you should now use assertions for forced program terminations. The values transferred using the FIELDS addition of the ASSERT statement are usually better suited to problem analysis than a message.

Exception

Exit messages can still be used, if it is absolutely necessary to display message text in the short dump of the runtime error. However, this should not be misunderstood as communication with the user. A runtime error is not a suitable way of communicating with users. For a simple, unconditional program termination, however, you should no longer use exit messages. Instead, you should specify a logical condition in ASSERT that is always false.