An effective way to pass JSON between Java and JavaScript

I'm new to nashorn and write scripts on the JVM, and wonder if I can make my java code communicate with JavaScript more effectively

I am using the third-party JS library used with JS objects. In my java code, I will transfer the data as map < string, Object > data

Because the third-party JS wants to use ordinary JS objects, I can't pass data as it is, although the script engine allows you to access the map as if it were an ordinary JS object

The script I'm using uses' hasownproperty 'on the data parameter and fails to call on the Java object

When I try to use object prototype. hasOwnProperty. When calling (data, 'myprop'), it does not work and always returns' false ' The basic problem is that Java object is not a JavaScript object prototype

I finally did this:

Map<String,Object> data;

ObjectMapper mapper = new ObjectMapper();   
String rawJSON = mapper.writeValueAsString(data);

ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");

engine.eval('third_party_lib.js');
engine.eval('function doSomething(jsonStr) { var jsObj = JSON.parse(jsonStr); return doSomethingElse(jsObj); }');
Object value = ((Invocable) engine).invokeFunction("doSomething",rawJSON);

This works as expected, but all these round-trip JSON parsing is heavy, and it feels that there may be a simpler, faster and more direct way to do this

So, is there a better way to pass JSON between Java and JavaScript or create compatible JS objects in my java code?

I've seen this use mustache JS template rendering guide, but it does almost exactly the same

thank you!

Solution

Nashorn specializes in Java util. Map object Nashorn allows map keys to be treated as "attributes" See also https://wiki.openjdk.java.net/display/Nashorn/Nashorn +extensions#Nashornextensions-SpecialtreatmentofobjectsofspecificJavaclasses

Therefore, if your map contains "foo" as the key, the script can access mapobj Foo to get its value It doesn't matter if the script you evaluate is a third-party script As long as the script is evaluated by nashorn, nashorn will specifically link the map attribute to access and get the results you want This approach avoids unnecessary JSON string conversion and parsing round trips (as you mentioned yourself)