NPE because ConsequenceMetaData.toString is not null-safe --------------------------------------------------------- Key: DROOLS-673 URL: https://issues.jboss.org/browse/DROOLS-673 Project: Drools Issue Type: Bug Affects Versions: 6.1.0.Final Reporter: george thomas Assignee: Mario Fusco Priority: Minor Attachments: ConsequenceMetaData.NPE.log The {{toString()}} method in {{org.drools.core.rule.ConsequenceMetaData}} is not null-safe. It assumes that the {{List}} {{statements}} contains at least one element. This is a problem when the method gets invoked during the serialization-based deep clone effected during initialization under certain conditions (see the "Reproduce" section). With this combination, code in {{java.io.ObjectOutputStream}} ends up invoking the {{toString()}} method in order to print additional information in the stack trace for {{java.io.NotSerializableException}}. I have attached a snippet of the stack trace as a reference. The code in question is unchanged even in the [latest version in github|https://github.com/droolsjbpm/drools/blob/master/drools-core/src/m...].