C.3.21. WARNING: An illegal reflective access operation has occurred

Last Updated: 2020-01-21

Condition or Error

The following Warning may be seen in the Manager Logs when running v6.1.2 and above in conjunction with Java 9 and above

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.drools.core.rule.builder.dialect.asm.ClassGenerator 
to method java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int)
WARNING: Please consider reporting this to the maintainers of org.drools.core.rule.builder.dialect.asm.ClassGenerator
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release


  • This is a known issue due to new encapsulation controls in Java 9+


  • This warning does not affect operations of the Cluster and can be safely ignored