Kermeta provides also an exception mechanism. You can define a "rescue" block to manage errors occurring during the execution of another block. Exception mechanism is very close to the Java Exception mechanism.

Example 1 : a simple exception raising

do
    var excep : kermeta::exceptions::Exception
    
    excep := kermeta::exceptions::Exception.new
    stdio.writeln("Throwing an exception ! ")
    raise excep
end

Any block can then rescue exceptions.

Example 2 : rescue block

var v1 : Integer init 2
var v2 : Integer init 3

do
    var v3 : Integer
    v3 := v1 + v2
rescue (myConstraintError : kermeta::exceptions::ConstraintViolatedInv)
    // something with myConstraintError
    // ...
rescue (myError : kermeta::exceptions::Exception)
    // something with myError
    // ...
end