KF

Definitions

Feature Definition Files

A Feature is a group of types, resources and [BON] immutables objects defined using two files that shall be in Application classpath:

[featureName].kf, a Java properties file. Keys are described in the “Feature definition file properties” table below.
[featureName].cert, an X509 certificate file that uniquely identifies the Feature

Feature definition file properties
Key	Usage	Description
entryPoint	Mandatory	The fully qualified name of the class that implements ej.kf.FeatureEntryPoint
immutables	Optional	Semicolon separated list of paths to [BON] immutable files owned by the Feature. `[BON]` immutable file is defined by a `/` separated path relative to application classpath
resources	Optional	Semicolon separated list of resource names owned by the Feature. Resource name is defined by Class.getResourceAsStream(String)
requiredTypes	Optional	Comma separated list of fully qualified names of required types. (Types that may be dynamically loaded using Class.forName()).
types	Optional	Comma separated list of fully qualified names of types owned by the Feature. A wildcard is allowed as terminal character to embed all types starting with the given qualified name (`a.b.C,x.y.*`)
version	Mandatory	String version, that can retrieved using ej.kf.Module.getVersion()

Kernel Definition Files

Kernel definition files are mandatory if one or more Feature definition file is loaded and are named kernel.kf and kernel.cert. kernel.kf must only define the version key. All types, resources and immutables are automatically owned by the Kernel if not explicitly set to be owned by a Feature.

Kernel API Files

Kernel API file definition is explained here: Kernel API.

Access Error Codes

When an instruction is executed that will break a Kernel & Features Specification (KF) insulation semantic rule, a java.lang.IllegalAccessError is thrown, with an error code composed of two parts: [source][errorKind].

source: a single character indicating the kind of Java element on which the access error occurred (Table “Error codes: source”)
errorKind: an error number indicating the action on which the access error occurred (Table “Error codes: kind”)

Error codes: source
Character	Description
A	Error thrown when accessing an array
I	Error thrown when calling a method
F	Error thrown when accessing an instance field
M	Error thrown when entering a synchronized block or method
P	Error thrown when passing a parameter to a method call
R	Error thrown when returning from a method call
S	Error thrown when accessing a static field

Error codes: kind
Id	Description
1	An object owned by a Feature is being assigned to an object owned by the Kernel, but the current context is not owned by the Kernel
2	An object owned by a Feature is being assigned to an object owned by another Feature
3	An object owned by a Feature is being accessed from a context owned by another Feature
4	A synchronize on an object owned by the Kernel is executed in a method owned by a Feature
5	A call to a feature code occurs while owning a Kernel monitor

Feature Installation and Loading Error Codes

When an error occurs during the installation of a Feature via the Kernel.install(InputStream) method, or during the loading of installed Features at bootstrap, the system may throw an ej.kf.InvalidFormatException.

This exception carries a specific error code, which can be retrieved by calling the getMessage() method on the InvalidFormatException instance. The returned message will follow the format: code=<id>, where id corresponds the specific error encountered.

Error code 3 indicates that an unexpected exception occurs during Feature installation (e.g. code=3:<exception_type>).

When the exception type is java.lang.OutOfMemoryError, it may indicate there is not enough space in the Managed Heap to load the Feature’s metadata section. If sufficient memory is available or if a different exception type is reported (e.g. code=3:java.lang.ArrayIndexOutOfBoundsException), this likely points to a corrupted Feature file.

Error codes ranging from 50 to 100, thrown during Feature installation, indicate an error returned by the LLKERNEL Abstraction Layer.

Feature Installation Error Codes Related to LLKERNEL Implementation
Id	Description
51	The `LLKERNEL_impl_copyToROM()` function returned an error.
52	The maximum number of installed Features is reached.
54	The address returned by the last call to `LLKERNEL_impl_getFeatureAddressRAM()` or `LLKERNEL_impl_getFeatureAddressROM()` does not match the alignment constraint.
55	The address returned by the last call to `LLKERNEL_impl_getFeatureAddressROM()` overlaps with a previously returned address.
56	The address returned by the last call to `LLKERNEL_impl_getFeatureAddressRAM()` overlaps with a previously returned address.
58	The `.fo` file cannot be installed on this Kernel because it contains a code chunk section with a size greater than this Kernel code chunk size.
59	The `LLKERNEL_IMPL_allocateFeature()` function returned `0`. The Feature cannot be allocated in memory.

Those thrown at Kernel boot indicate an issue with an already installed Feature, such as memory corruption or Feature link incompatibility after Kernel update.

Installed Feature Loading Error Codes
Id	Description
53	The installed Feature content has been corrupted (CRC check error).
57	The address returned by the last call to `LLKERNEL_impl_getFeatureAddressRAM()` is not the same than the one returned when the Feature has been installed.
60	The `LLKERNEL_IMPL_getFeatureHandle()` function returned `0`. The handle for an installed Feature could not be retrieved as expected.

Error codes ranging from 150 to 180, thrown during Feature installation, typically indicate an invalid or a corrupted Feature file.

Corrupted Feature File

A corrupted Feature is most likely the result of an issue during the streaming transfer of the .fo file. This is typically caused by an incorrect implementation of the java.io.InputStream instance passed to the Kernel.install(InputStream) method.

If your InputStream is provided by a Foundation Library, ensure that your VEE Port has been successfully qualified. For example, when using a java.io.FileInputStream, verify that the File System port has been fully validated. The Feature loader relies on InputStream.skip(long), which is not commonly used. Be sure this method is correctly implemented, particularly with regard to handling the 64-bit long argument.