webMathematica™ Wolfram - Wolfram Research

webMathematica User Guide 183java.lang.NoClassDefFoundError: com/wolfram/jlink/MathLinkExceptionat java.lang.Class.newInstance0(Native Method)at java.lang.Class.newInstance(Class.java:237)This means that J/Link is not installed correctly; specifically the J/Link Java archive has notbeen located by the Java system. This archive is called JLink.jar. Since webMathematicacontains its own version of J/Link, this problem should not be observed, and you should contactsupport for assistance.NoSuchMethodError: KernelDataIf you find that webMathematica does not work, you may notice in the initial web page or in theservlet log a report of a NoSuchMethodError exception that is generated inside of the starÖtInit method of the KernelData class. An example is shown below.java.lang.NoSuchMethodError atcom.wolfram.kerneltools.KernelData.startInit(Unknown Source) atcom.wolfram.kerneltools.KernelPool.initKernels(Unknown Source) atcom.wolfram.kerneltools.KernelPoolManager.acquireKernelPool(UnknownSource)This will occur if you try to run webMathematica with an older version of J/Link. This can hap-pen if, at some time in the past, a copy of JLink.jar was installed directly into the Java run-time. In general, it is not a good idea to install classes into your Java runtime, because theseclasses will always be loaded even if a newer version is made available, as happens with thiserror. The solution is to search in your copy of Java for JLink.jar and remove it. You shouldalso search for and remove the native library JLinkNativeLibrary, which is often found in theSystemFiles directory. webMathematica has its own copy of J/Link and there is no need toinstall J/Link into the Java runtime.Debugging webMathematicawebMathematica involves running computations inside a server. This poses a number of problemsand constraints for investigating why it does not work as you intend. The best way totrack down issues is to use Wolfram Workbench to connect to the server and debug your code.