How to use rapc from RIM… dirty details!

What’s really going on in rapc, Blackberry’s crazed compile tool? Let me begin by telling you that everything you’ve read until this point is not entirely accurate. There are those that will tell you that you have to run preverify.exe prior to running rapc. Then there are those who will tell you that the bb-ant-tools are sufficient. There are people that complain that the RIM compiler has bugs in it. (This may be true but I’ve so far been able to fix broken builds by using all of the advice I’m including here.) I’ve also found a blog that claims you can build from non-Windows operating systems. I’ve read in some places that either WTK or the JDE must be in the PATH so that rapc can find a preverifier. While some of these tips, tools, tutorials work they all have limits. Eventually you’ll find your application either throws random NPE’s, verification errors, or infinitely reboots the device! Now pay attention!

Now let me explain my project. I have a little bit of dependency injection going on via source generation. Then I also have some external jar dependencies. All of this creates a bit of a challenge for basic rapc invocation. In order to generate my midlet cod file I need to:

• Run a source generator
• Include the generated source in my list of things to compile
• somehow include my external jar dependencies in the compile.
• Include resources in my compiled output
• Pick up my suit from the cleaners
• Get the entire thing to run on my Mac?

While the last bullet is entirely optional and irrelevant, I include it because its the only way to get completely familiar with rapc. That is, if I can meet/greet/beat the challenge of cross platform compilation of Blackberry then I’ll really understand the intracacies of compiling with rapc. Now onto the juice.

How Rapc works… I think…
There are various approaches to compiling Blackberry applications that I know of.

• Compile your app against the MIDP and CLDC APIs (include either WTK or MPowerplayer or someother party’s midp and CLDC jars on your bootstrap classpath for javac… making sure you use javac1.3 or below), preverify with JDE preverify.exe (found in %JDE_HOME%/bin), jar and finally compile with rapc.
• Compile your application source files entirely with Rapc.

The first option has problems because there’s the possibility that javac will generate class files that will cause verification errors or (as my team discovered recently) the white screen of death when loaded onto the device. The second option has problems because it’s very tricky and prone to the same errors unless you are very dillegent. It took a lot of head banging and trial/error to come up with these details so read closely.

How do we use rapc? This is the question that still plagues me. There’s little documentation around the nuances you’ll encounter when invoking the rapc compiler from the command line. The rapc compiler is an executable (.exe) file in the JDE install directory living under the bin subfolder. First thing to note is the rapc.exe just delegates everything to rapc.jar. That means the same exact command line parameters you would use with rapc.exe will work with rapc.jar. (Call the jar with the “java -jar” command.) The most important thing to understand is that you cannot mix and match. That is you cannot use the output of javac/WTK preverify to fuel rapc. Furthermore you need to pay strict attention to the version of the JDE you use because it must be the same (or earlier) version of your target platform. For eg., if you intend to target Blackberry devices running a 4.2.2 OS you should use the compiler tools from the JDE version 4.2.2 or earlier. If you don’t pay attention to this step your product will work just fine until it’s time to ship… at which time you’ll experience weird, impossible to track/reproduce on a developer workstation, errors. There are other important tools in the JDE that you’ll need as well. The preverify tool is required (unless you’re using JDE 4.3.0 and targeting OS 4.3+) as well as the SignatureTool.jsr. Finally there is the net_rim_api.jar which lives under the lib folder in the JDE install directory. The next big thing to understand is the command line options.

import
Use the import= to specify the location of the net_rim_api.jar. This flag takes the relative or absolute path of not only the rim APIs but any other jar or cod dependencies your application has. (I haven’t tried cod dependencies but the docs say you can list cod files.) Be careful because this is only for resolving dependencies. Anything you list here will not be included in the final output cod. What this means is any jar files listed here must either be compiled as separate cod libraries or their source files somehow inlined in the final compiled. Dependencies listed here are scope as provided. In other words it is assumed they will be made available at runtime by either the RIM platform or by some pre-installed package.

codename
(codname for 4.3.0+)
This parameter threw me for a minute when I attempted to roll back to an earlier version of the RIM compile toolchain. I believe (and I need to double check and update this fact later) that rapc version 4.3.0 and higher expect a codname flag while versions prior to 4.3.0 expect a codename flag. The value you specify here will be the value used in the output codfile name. Paths can be relative to the working directory (the folder rapc is called from) or possibly absolute paths. For instance if you give build/MyApp as the value then rapc will spit all of its output into the build folder relative to the working directory giving you a final MyApp.cod file there. (you’ll also have MyApp.jar, MyApp.csi, MyApp.debug and other files in this folder.)

midlet
This is the application type. Use this flag if you plan to develop a J2ME spec compliant midlet. Blackberry support another application type, cldc, which provides RIM specific features (more on that in possibly another post) and is specified by the mutually exclusive -cldc flag. A You have to -midlet or -cldc to specify which kind of application you are building.

cldc
Use this flag if your are building a CLDC application that adheres to RIM’s proprietary launching interfaces. CLDC apps offer abilities to run in the background and be started at device boot time. There are other hidden gems here that I’d have to get into with another post.

jad
Use this parameter if you have a JAD file that includes your application’s meta data. This parameter is optional as you may substitue a .rapc file to include the meta data. Application meta data includes things like the icon to display on the desktop, the midlets contained in your aplication bundle, runtime properties, etc. Referr to the J2ME midlet spec for more detail.

rapc file
This would be the path to a “.rapc” file that includes meta data about your application. I’ll probably follow up with another post to explain the details behind this proprietary RIM spec. While a JAD file also includes meta data there are certain properties that can be included in this file that cannot be included in the JAD file and vice-versa.

class or java files
The last parameter should specify either a jar file containing the compiled classes or be a list of the .java files you intend to compile. Here’s where rapc gets really interesting. If you precompile your “.java” files you had better be certain you run the RIM preverify tool against these class files prior to invoking the compiler. Also I will repeat that you must use the same (or earlier) version preverify as your target platform. For eg., if you intend to target Blackberry devices running a 4.2.2 OS you should use both RIM’s rapc and preverify tools from the JDE version 4.2.2 or earlier. If you don’t pay attention to this step your product will work just fine until it’s time to ship… at which time you’ll experience weird, impossible to track/reproduce on a developer workstation, errors. (I said this before didn’t I?) Rapc is very picky here and the behavior varies between versions. It first calls out to javac assuming that the Java compiler is in the PATH. It then passes the output from javac to preverify. Note that in JDE 4.3.0 both “.java” source compiling and preverification is done from within the rapc.jar while earlier versions of rapc call out to the command line using the command “preverify” (not “preverify.exe”… this is an important distinction) and passing standard preverify parameters. Finally it creates the final “.cod” that will run on the device. What is included in the cod file depends on what is passed on the command line and what’s available from the working directory. For instance, your application icon (and I found this through trial and error) must be locatable from the working directory unless you specify an absolute path in the jad file. If you compile a jar file (not recommended for rapc prior to 4.3.0) then everything in that jar file (images, multimedia files, application resources, etc.) will be included in the final cod file. If you compile “.java” files directly from rapc then no application resources will make it into the final output cod file, only the compiled .class files will be there (along with the application icon specified in the jad if it can be found from the working directory). It took a lot of banging my head to figure this out. Finally instead of a jar file or space delimited list of “.java” files, you can specify a text file that lists (new line delimited style) all of the “.java” files you wish to pass to the compiler. This is a potential work-around to command line size restrictions that may be present on some versions of Windows. This file should be given with an @ prefix. For eg. if your have a MyApp.txt file then the last parameter for rapc will be @MyApp.txt. This is the preferred method of giving files to rapc because as your application grows so will the list of files.

One last got’cha I found was with trying to use rapc.jar directly instead of rapc.exe. If you are running a JDE earlier than 4.3.0 then you’ll get into trouble here because there is a secret parameter passed from rapc.exe that RIM won’t tell me about. Because the command line syntax for the jar is identical to the command line syntax for the “.exe” you can almost get away with it but because of a secret exchange happening between the Jar and exe you’ll get undefined behavior and weird errors in certain circumstances. This last gotcha is what makes it impossible to compile on an OS other than Windows while targeting a RIM OS earlier than 4.3.0.

In the end I’ve determined that it is not possible to accurately build a blackberry application on an operating system other than Windows. Also while there may be some truth to the myth of bugs in rapc I believe it all boils down to a bunch of nasty assumptions the RIM developers made during the design. (they assumed everyone would be so thrilled with their Swing based IDE that they would throw away Eclipse/Idea/Netbeans and burn their Macintosh laptops in celbration of the obviously superior RIM tool chain.) I do believe that if you pay close attention to the details outlined above you can diagnose most preverification and random erros you may be suffering from. I plan to revist this topic in the future as I’ve taken a break from mobile and begun work on some other things. However I do not plan to let rapc defeat me entirely. Keep an eye out because I’ll likely be updating this very same post with more details.