graal.js compatibility problem

[lordk911]

I have some code originally run on nashorn , when change to graal.js , the code not work.

My code will pass a java object as parameter to a js function.

The java object struct is :

public class AggregateResult {
    private List<ColumnIndex> columnList;
    private String[][] data;
    private String resultQuery;
    private long datasetId;
    private String aggConfig;

and the js function will use the object ,read out the data :

for (var i = 0; i < aggData.data.length; i++) {
        var newKey = getRowElements(aggData.data[i], keysIdx);
        var jk = newKey.join('-');
        if (_.isUndefined(joinedKeys[jk])) {
            castedKeys.push(newKey);
            joinedKeys[jk] = true;
        }

when use graal.js as ScriptEngine , an ERROR will throw out and tell me the aggData's data property is undefine when code run to :
aggData.data.length

[lordk911]

I've tried to enable js.nashorn-compat=true , and the issues I mentioned above is gone. But I have another parameter which type is com.alibaba.fastjson.JSONObject. graal.js can't read it's property

[wirthi]

Hi @lordk911

thanks for your question.

com.alibaba.fastjson.JSONObject seems to be a java.util.Map implementation. We currently do not special-case Maps in any way. This means, you can access a Java map from JavaScript just as you can in Java, by calling e.g. get and set. https://github.com/oracle/graaljs/blob/master/docs/user/JavaInteroperability.md#map-access I assume what your code tries to do is to access it with JavaScript's property access, e.g. print(javaMap.key). This does not work currently, you need to rewrite that to print(javaMap.get('key');. For the methods to be available, you need to have HostAccess enabled when creating the ScriptEngine/Context.

Another option is to wrap your Map into a ProxyObject. Then you can limit the changes to the JavaSide and need not change the JavaScript code. For a flat array, use ProxyObject.fromMap(yourJavaMap) on the Java side before passing the result to JavaScript (e.g. via a binding). For complex (nested) data structures, you will need your own implementation of the ProxyObject interface.

Best,
Christian

[lordk911]

Thank you. I understand.

[Phillipus]

@wirthi

Thanks for you answer. I just ran into this same situation. I tried your suggestion of using ProxyObject.fromMap(yourJavaMap) and it works. But I was wondering...

This does not work currently

Are there plans to implement JS property type access on java.util.Map without using a ProxyObject?

[wirthi]

Hi @Phillipus

yes this is planned, see e.g. #143

This is quite complicated as we have to implement it in the Truffle framework, so make it compatible with all programming languages we support (not just JavaScript). The Truffle team is working on it, but I don't think there is an ETA for that currently.

Best,
Christian

[Phillipus]

@wirthi Thanks for the info, I appreciate it. No hurry, as ProxyObject is working for me.