Hi Eoin,
I did some additional work to search for the cause of your incompatibility issue, rather than only give a possibly inflexible solution that simply says make sure everything matches up.
The MATLAB Builder JA produces JAR files that depend on javabuilder.jar. When a class contained in javabuilder.jar is instantiated for the first time, a series of things occur. Your issue occurred in the second step.
- Dependent classes in javabuilder.jar are loaded
- Static initialization of dependent classes triggers loading of a series of shared libraries in the MATLAB Compiler Runtime (MCR), which is found via the runtime file mclmcrrt7_16.dll ...
Why 32 vs 64 bit MATLAB install matters: There are two differences between these installs relevant to this issue. For a 32 bit MATLAB install, a folder with a 32 bit compiled mclmcrrt7_16.dll is placed in folder in <32bitmatlabroot>/R2011b/runtime/win32, and a 32 bit compiled version of javabuilder.jar is placed in <32bitmatlabroot>/R2011b/toolbox/javabuilder/jar. For a 64 bit MATLAB install, a folder with a 64 bit compiled mclmcrrt7_16.dll is placed in folder in <64bitmatlabroot>/R2011b/runtime/win64, and a 64 bit compiled version of javabuilder.jar is placed in <64bitmatlabroot>/R2011b/toolbox/javabuilder/jar.
Why 32 bit versus 64 bit Java compilation matters: It doesn't as far as I know. However, it may be the case that paths are set differently inside the 32 bit javabuilder.jar and the 64 bit javabuilder.jar. They are not byte identical and I did not investigate further as the issue doesn't seem to reside here.
Why 32 bit versus 64 bit java application launcher matters: When your Java application instantiates a class in javabuilder.jar, and in my experiments it didn't matter whether I called the 32 bit or 64 bit javabuilder.jar files in any scenario (and this seems to make sense given the point above), then depending on whether the JVM the code is running in is either 32 bit or 64 bit will cause javabuilder.jar to make a decision to either look for a 32 bit mclmcrrt7_16.dll or a 64 bit mclmcrrt7_16.dll in your PATH environment variable, respectively. For example, if you installed MATLAB 32 bit and try to run your application with the Java 1.7 64 bit java command then then javabuilder.jar in your classpath will look in your PATH environment variable for a 64 bit mclmcrrt7_16.dll. The 32 bit mclmcrrt7_16.dll is not considered a suitable choice and even if that is in your classpath you will receive a 'java.lang.UnsatisfiedLinkError: Failed to find library mclmcrrt7_16.dll'. Unlike the Java javabuilder.jar files, whether the C/C++ files in mclmcrrt7_16.dll have been compiled via 32 bit or 64 bit compilation matters. The same would go for installing MATLAB 64 bit, thus putting <64bitmatlabroot>/R2011b/runtime/win64 in your PATH environment variable automatically during the install, and trying to run an application with your generated Java code via the Java 1.6 32 bit command java. A class in javabuilder.jar would then try to look for a 32 bit compiled mclmcrrt7_16.dll and only find a 64 bit version, which it would not find suitable and throw a java.lang.UnsatisfiedLinkError.
What do you need to do to ensure compatibility? If you try running your Java application with Java 1.X 32 bit then ensure a 32 bit compiled mclmcrrt7_16.dll is available via your PATH environment variable (normally under a folder named 'win32'). If you try running your Java application with Java 1.X 64 bit then ensure a 64 bit compiled mclmcrrt7_16.dll is available via your PATH environment variable (normally under a folder named 'win64'). The mclmcrrt7_16.dll file is placed when you install MATLAB on your development machine or the MCR on a target deployment machine. Though it made no difference in my experiments, I would also suggest you place in your classpath when calling the java command the javabuilder.jar under <xxbitmatlabroot>/R2011b/toolbox/javabuilder/jar/win32 when you run with Java 1.X 32 bit java command and <xxbitmatlabroot>/R2011b/toolbox/javabuilder/jar/win64 when you run with Java 1.X 64 bit java command. Both of these javabuilder.jar files are included in the 32 bit and 64 bit MATLAB installs.
Sorry for the novel, but I hope this sheds some light on what was causing your error. I recreated it in a variety of ways and ran experiments to check all my conclucions. If there are errors in my reasoning, please let me know!
Cheers,
Kyle
