MVEL allows you to disable the JIT compiler if for whatever reason it is undesirable to be generating classes. There are two ways of doing this:

• Via the system property mvel.disable.jit
• Through the OptimizerFactory class

The first way is straight forward (as a parameter to the JVM):

-Dmvel.disable.jit=true

The second way is straight forward, but worthy of some additional explanation:

OptimizerFactory.setDefaultOptimizer("reflective");

MVEL uses pluggable optimizers to deal with optimizing the AST and acessors, and is therefore the reason for the use of a named optimizer here, in this case reflective.