practical rdpi managing message descriptions

7/29/2019 Practical Rdpi Managing Message Descriptions

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Practical RDPi: Managing Message Descriptions

Written by Joe Pluta

Wednesday, 06 October 2010 00:00 - Last Updated Wednesday, 06 October 2010 00:00

Message descriptions are one of the unsung heroes of IBM i application development,

and this article shows you how to use RDPi to manage them with ease.

The message description is unique to the IBM i. The concept is simple: a seven-character key

provides a link to a fully featured message, which supports both a short version suitable for

presentation on a user display and a long message with enough information to provide full

diagnostic and help capabilities. Such a basic idea, yet message descriptions provide a wide

range of capabilities. For example, messages are contained in a message file,m and

internationalization is as simple as supplying a different message file for the locale. The i had

i18n before i18n was cool! Using Message Fields TodayMessages are incredibly feature-rich. You can design a message with replacement variables

and also design a data record that is passed to the message at run time. This message data isthen parsed when the message is displayed, and the variable data is inserted into the message.

Here's a simple example in which the customer number and name is displayed as an

informational message:

Customer &1, name &2.

The message is further defined to identify the size of the two variables, &1 and &2, and thenwhen the application program sends the message to the user, it passes a data structure with

the appropriate values and the message is displayed with the data in place. Given the power of

messages, it may seem surprising that they're not universally used. But I think that message

files are a little bit like externally described printer files: the pain of the standard tooling is just

enough to prevent the adoption of the tool. The good news is that, like printer files, the Rational

tooling provides easier-to-use capabilities to get you over the hump and using messages in your

everyday programming. Not only that, but the message file capabilities are present all the way

back to WDSC, so even folks who haven't made the move to the newer Rational tool sets can

still use these techniques (that's unfortunately definitely notthe case with printer files).

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Figure 1: The CHGMSGD command is not the most user-friendly command in the itoolkit. (Click images to enlarge.)

The problem with message files lies in their maintenance. Take a look at Figure 1. TheCHGMSGD command is almost useless for maintenance. The keyword values throughout thecommand are not filled in with the current definitions from the message; they instead onlysupport the dreaded *SAME keyword, which means you have to key in the whole new value.This is not only annoying for things like text, but also almost impossible to use when yourmessage data has many variables; you effectively have to key in all the variables every timeyou make a change. And I'm not just complaining to hear myself talk: check out theCHGUSRPRF command. Execute CHGUSRPRF on a user profile to which you have authority(such as your own) and hit F4; you'll see that most of the values are pre-filled. CHGMSGD justdoesn't work that way.

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Figure 2: WRKMSGF has a little more functionality.

The WRKMSGF command gives you a little better interface. It's still rather labor-intensive, asyou can see in Figure 2; you have to first call up the message file, then position to the messagedescription, and then finally maintain the message. It does pre-fill the values for the keywordsbased on the current message definition, a feature that is absolutely essential when maintainingmessages with many message data fields. But it's far from an easy experience, and making anysort of wholesale changes is out of the question.

The other problem is that a message file is like a number of other objects in the system,particularly non-program objects such as output queues and subsystem descriptions, in that itdoes not have a source member that is compiled to create the object. You create these objectsby executing commands from the command line. Since command-line changes are ad hoc, youalways have the chance of somebody making a change that wipes out yoursor even deletingthe objectand then your changes are lost. This argues for a practice I try to implement at allmy client sites: I always have a source file that contains all the commands used in defining ormodifying system objects.RDPi and Message Files

So how does RDPi make message file management easier? Well, at first glance, you might

think that Remote Systems Explorer (RSE) has your back, but unfortunately that turns out not tobe quite true.

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Figure 3: RSE has some nice inquiry capabilities for message files.

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Figure 4: But the maintenance capabilities are the same as the CHGMSGD, which is tosay not very good.

Looking at Figure 3, you can see that the Remote System Explorer (RSE) will show you themessage file and the messages in it. You can even initiate a change using the right-click contextmenu. However, the change isn't particularly user-friendly. RSE uses its built-in ability toexecute any IBM i command. Unfortunately, that ability is limited by the features of thecommand being executed, which, in the case of the CHGMSGD, are somewhat underwhelming,as we've already seen. But even if the RSE change feature was more powerful, I still wouldn'trecommend it, because of the ad hocnature of the change. Instead, I recommend a source-fileapproach. In my library, I created source file QSRC1009 with a CLP member MYMSGF. Here'sthe source for that member:

MYMSGF: PGM

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DCL &MSGF *CHAR 10 VALUE('MYMSGF')

DCL &MSGFLIB *CHAR 10 VALUE('MCP')

MONMSG CPF2419

RMVMSGD MSGID(CUS0001) MSGF(&MSGFLIB/&MSGF)

ADDMSGD MSGID(CUS0001) MSGF(&MSGFLIB/&MSGF) +

MSG('Customer &1, name &2.') +

FMT((*DEC 6 0) (*CHAR 30))



MSG('No customer number passed.')



MSG('Invalid opcode.')



MSG('Feature not yet implemented.')

ENDPGM

This is the standard template I use for all "message file compile" programs. I put the name ofthe message file and library into variables at the top of the program; that way, I don't have tochange every line of the source if the message file name or library needs to change. I do aRMVMSGD and an ADDMSGD; this works whether the message exists or not. The MONMSGCPF2419 ignores any errors if I execute a RMVMSGD on a message that doesn't exist. UseRDPi to maintain the file; it's very easy to copy and paste an existing message descriptiondefinition to create a new one.

You'll note that I did just that: I added a new message that doesn't appear in Figure 3, messageID CUS9999. Next I have to compile the program. However, this program is a little different thanothers; it's a setup program rather than an application program. Unlike application programs,which you only need to compile, you have to compile a setup program and then run it. Thecompile part is easy in RDPi; options include pressing Ctrl+Shift+C when you're in the editorand right-clicking on the member in the RSE view and selecting Compile. But running a programfrom RDPi is not always the easiest. You can run any command by right-clicking on the Objectssubsystem and selecting Run Command or by using the command field in the Commands Logtab, and these are both options I'll address a little more another day. Unfortunately, they bothsuffer from the same flaw: you have to key in the entire command, such as CALL MYMSGF.This is tedious and error-prone, being subject to the whims of both typographical errors andlibrary list malfunctions.

To close this article, I would like to show you one extra feature.

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You can run the program in one of two ways. The first is straightforward: expand your libraryand look for the program. When you find it, right-click on it and select Run As > IBM i applicationin RSE Job, as shown in Figure 5. It's easy, but it does require looking for the program. I haveone other little trick. If your source file is in the same library as your setup program (not anunreasonable notion, especially for these sorts of programs), you can set up a User Action.Figure 6 shows the definition of the action, while Figure 7 shows how to use the action.

Figure 5: The simplest way to run a program is to right-click on the program object andselect Run As.

Figure 6: A more convenient way, though, is to use a User Action, like the one shownhere.

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Figure 7: Then you can right-click on the source member and invoke the User Action tocall the program.

You might wonder why I create the user action when the Run As option is perfectly adequate. Ido it because it allows me to keep my focus on the source file. Libraries tend to get clutteredwith objects, and having to search for the appropriate program to run can require enoughscrolling to make things cumbersome; in Figure 5 I had to scroll all the way to the top of thelibrary to find the program. Instead, with the user action, I do everything from the source file: Idouble-click on the source member to edit it, make my changes, hit Ctrl+Shift+C to save andcompile the member, and then right-click on the same source member to run the resultingprogram. It's simple and quick.

In fact, I hope the technique is quick enough that those of you not using message files might bewilling to give it another shot. And at the same time, I hope the message file mavens among ushave learned a little something from this article as well. I may devote another article to the fineart of defining and naming messages and using them in conjunction with another IBM iexclusive: the message subfile.

as/400, os/400, iseries, system i, i5/os, ibm i, power systems, 6.1, 7.1, V7,

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practical rdpi managing message descriptions

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