Package org.apache.tinkerpop.gremlin.jsr223

Class GremlinLangScriptEngine

java.lang.Object
javax.script.AbstractScriptEngine
org.apache.tinkerpop.gremlin.jsr223.GremlinLangScriptEngine
All Implemented Interfaces:
ScriptEngine, GremlinScriptEngine
public class GremlinLangScriptEngine extends AbstractScriptEngine implements GremlinScriptEngine
A GremlinScriptEngine implementation that evaluates Gremlin scripts using gremlin-language. As it uses gremlin-language and thus the ANTLR parser, it is not capable of process arbitrary scripts as the GremlinGroovyScriptEngine can and is therefore a more secure Gremlin evaluator. It is obviously restricted to the capabilities of the ANTLR grammar so therefore syntax that includes things like lambdas are not supported.

As an internal note, technically, this is an incomplete implementation of the GremlinScriptEngine in the traditional sense as a drop-in replacement for something like the GremlinGroovyScriptEngine. As a result, this GremlinScriptEngine cannot pass the GremlinScriptEngineSuite tests in full. On the other hand, this limitation is precisely what makes this implementation better from a security perspective. Ultimately, this implementation represents the first step to changes in what it means to have a GremlinScriptEngine. In some sense, there is question why a GremlinScriptEngine approach is necessary at all except for easily plugging into the existing internals of Gremlin Server or more specifically the GremlinExecutor.

The engine includes a cache that can help spare repeated parsing of the same traversal. It is keyed to each configuration of the GraphTraversalSource that initially requested its execution via the bindings given to the eval method. Each cache is keyed on the original Gremlin string and holds the initialized parsed traversal for its value. If that Gremlin string is matched again in the future, it will use the one from the cache rather than parse again via the ANTLR grammar. In addition, if GValue instances were used in formation of the traversal, it will substitute in new bindings given with the eval.