Conditional has() - gremlin

Question

I am building a query based on passed parameters. For example, if pass p1='a' and p2='b', my query will look something like this:
g.V()
.has("p1","a")
.has("p2","b")
If let's say p2 is not passed, then I won't have a second check:
g.V()
.has("p1","a")
Is it possible to perform parameter check inside the query instead of creating conditional checks for parameters before creating query?
Edit: Use case is based RESTful web service where I have something like, /server/myEndpoint?p1=a and endpoint implementation would build gremlin query with .has() steps solely based on presence of p1 or p2, so if p2 is not passed, query would look like in second snippet, and if passed would look like the one in first.

Answer 1

One possible approach is to build GraphTraversal until it's not executed:
Map<String, String> map = new HashMap<>();
map.put("p1", "a");
map.put("p2", null);
final GraphTraversal<Vertex, Vertex> v = g.V();
map.forEach((k,v) -> {
if(v != null) {
v.has(k,v);
}
});
return v.toStream().collect(Collectors.toList());

Answer 2

As a suggested improvement where you are creating the search, the Gremlin-optimized way to approach this would be through a parameterized script. In theory this would mean that you are building the query in a way which is looking for each parameter.
However, I don't believe there is an inherent "if" statement, per-say, so if you wanted to use the query to optionally handle your "Has" cases, it could be done with an "Or Step", an "And Step", or a "Choose Step". I would discourage it as a pattern, though. It is similar to how MySQL has the options to handle cases in Select queries: it would almost always be more performant and a better separation of concerns to bind the parameters right in the first place than to have the query builder sort out the programmatic logic.