Drools compiler does not recognize Java 9 ----------------------------------------- Key: DROOLS-2305 URL: https://issues.jboss.org/browse/DROOLS-2305 Project: Drools Issue Type: Bug Components: core engine Affects Versions: 7.5.0.Final Reporter: Jon Kranes Assignee: Mario Fusco The Drools compiler class org.drools.compiler.rule.builder.dialect.java.JavaDialectConfiguration does not include Java 9 as a valid language level. Instead, when run using Java 9, the assumed java version is set to the default value of "1.7". As a consequence, when compiling a rules file requiring Java 8 specific language features, the compilation will fail. For example, if a rule RHS contains the statement: {code:java} Arrays.asList("a","b","c").forEach(System.out::println); {code} The rule compilation fails with the error: {code:java} [ERROR] Unable to build KieBaseModel:default Rule Compilation error : [Rule name='test'] defaultpkg/Rule_test959974052.java (7:387) : Method references are allowed only at source level 1.8 or above {code} The problem can be worked around by adding a configuration file META-INF/kie.properties.conf containing the line: {code:java} drools.dialect.java.compiler.lnglevel = 1.8 {code} The Drools compiler code will use this value instead of the System "java.version" value, avoiding the problem.