MATLAB: Does the compiled application not locate a MATLAB built-in Java class with MATLAB Compiler 4.0 (R14)

builtclassclasspathinjavajavaclasspathm-codeMATLAB

I created an application and then compiled it with MATLAB Compiler. I am modifying the dynamic Java classpath in my MATLAB code using javaclasspath as follows:

javaclasspath('/usr/oracle/jdbc/classes12.jar')

My application works fine in MATLAB and on the development machine, but when I execute it on the deployed machine with the MCR, I receive the following error.

 ??? Undefined variable "com" or class "com.mathworks.toolbox.database.databaseConnect".
 Error in ==> database.database at 78
 Error in ==> testdb at 3
 MATLAB:undefinedVarOrClass

Best Answer

MATLAB Compiler uses the dynamic class path to reference JAR files used by any toolbox functions used in your application. This is because the MATLAB Compiler Runtime (MCR) only includes the base MATLAB functions, so JAR-files associated with individual toolboxes are packaged in the CTF-file. When executing the application in MATLAB, these JAR-files are on the static Java classpath, while in compiled applications they are on the dynamic classpath.

If your application needs to modify the Java classpath, you should retain any entries in the existing classpath and add the new paths. You can do this using the JAVAADDPATH function. For example:

javaaddpath('/usr/oracle/jdbc/classes12.jar')

This will prepend the directory to the dynamic classpath, leaving intact any JAR-files automatically added to the dynamic path by MATLAB Compiler.

For more information on JAVAADDPATH execute the following command at the MATLAB command prompt

doc javaaddpath

Related Solutions

MATLAB: How should I include a JAR file in the compiled application with MATLAB Compiler 4.1 (R14SP1)

In order to use a Java class in a compiled application, the JAR-file which contains the class or the CLASS-file need to be available on the deployment machine and the JAR-file or directory which contains the CLASS-file or package hierarchy need to be on the Java classpath in the deployed application.

The -a flag to the MCC command provides a simple mechanism to accomplish both of these requirements. When a JAR-file or CLASS-file is added with the -a flag, it will be added to the CTF-archive and when the application starts up, that JAR-file or CLASS-file will also be automatically added to the dynamic java classpath. If you are using DEPLOYTOOL instead of the MCC command, you can add the JAR-file or CLASS-file to the "Other files" folder.

The java classpath in the compiled application will not get updated correctly if you are using a CLASS-file which is part of a package but which is not in a JAR-file. This is because there is no way for DEPLOYTOOL or MCC to determine that the CLASS-file is part of a package. In this case you will need to manually modify the java classpath in the compiled application, for example by using JAVAADDPATH.

MATLAB: Do I get a warning stating “Invalid file or directory” when attempting to add a JAR-file to the dynamic Java class path in a deployable archive running on MATLAB Production Server

The "javaaddpath" function should not be used in deployed CTF-archives (or deployed applications in general). When a JAR-file is added to the "Files required for your archive to run" list, it will automatically be added to the dynamic path when the CTF-archive is loaded on MPS.

In cases where it is convenient to keep "javaaddpath" in the M-files when they run in MATLAB, one can use the "isdeployed" function to skip over calls to "javaaddpath" functions when run under deployment, as shown:

if ~isdeployed
    javaaddpath('lib/jconn2.jar');
end

Best Answer

Related Solutions

MATLAB: How should I include a JAR file in the compiled application with MATLAB Compiler 4.1 (R14SP1)

MATLAB: Do I get a warning stating “Invalid file or directory” when attempting to add a JAR-file to the dynamic Java class path in a deployable archive running on MATLAB Production Server

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