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在Java中运行JS面对的一大问题就是对象类型问题，本文对graaljs和Java之间不同类型的数据操作做了一些探索。

项目采用maven引入graaljs

pom依赖

<properties>
   <java.version>1.8</java.version>
   <graalvm.version>22.1.0.1</graalvm.version>
</properties>
<dependencies>
	<!-- fastjson2 -->
	<dependency>
		<groupId>com.alibaba.fastjson2</groupId>
		<artifactId>fastjson2</artifactId>
		<version>2.0.3</version>
	</dependency>
	
	<!-- graaljs 相关依赖 -->
	<dependency>
	   <groupId>org.graalvm.sdk</groupId>
	    <artifactId>graal-sdk</artifactId>
	    <version>${graalvm.version}</version>
	</dependency>
	<dependency>
	    <groupId>org.graalvm.js</groupId>
	    <artifactId>js</artifactId>
	    <version>${graalvm.version}</version>
	    <scope>runtime</scope>
	</dependency>
	<dependency>
	    <groupId>org.graalvm.js</groupId>
	    <artifactId>js-scriptengine</artifactId>
	    <version>${graalvm.version}</version>
	</dependency>
	<dependency>
	    <groupId>org.graalvm.tools</groupId>
	    <artifactId>profiler</artifactId>
	    <version>${graalvm.version}</version>
	    <scope>runtime</scope>
	</dependency>
	<dependency>
	    <groupId>org.graalvm.tools</groupId>
	    <artifactId>chromeinspector</artifactId>
	    <version>${graalvm.version}</version>
	    <scope>runtime</scope>
	</dependency>
</dependencies>

resource/a.js

const f = p => {
    p.a = "def";
    let r = {};
    r.msg = p;
    return r;
}

GraalJsDemo.java

package com.m.demo;

import com.alibaba.fastjson2.JSON;
import com.alibaba.fastjson2.JSONObject;
import com.iauto.mqtt.ruleengine.MqttRuleEngineApplication;

import javax.script.*;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.net.URL;
import java.util.function.Predicate;

public class GraalJsDemo {
    public static void main(String[] args) {
        ScriptEngineManager engineManager = new ScriptEngineManager();
        ScriptEngine jsEngine = engineManager.getEngineByName("graal.js");
        Invocable funcCall = (Invocable) jsEngine;

        Bindings bindings = jsEngine.getBindings(ScriptContext.ENGINE_SCOPE);
        bindings.put("polyglot.js.allowHostAccess", true);
        bindings.put("polyglot.js.allowHostClassLookup", (Predicate<String>) s -> true);

        try {
            URL jsResource = MqttRuleEngineApplication.class.getClassLoader().getResource("a.js");
            System.out.println("read file: " + jsResource.getPath());
            jsEngine.eval(new FileReader(jsResource.getPath()));
            JSONObject jsonObject = new JSONObject();
            jsonObject.put("a", "abc");

            Object res= funcCall.invokeFunction("f", jsonObject);
            System.out.println("invoke param: " + jsonObject);
            System.out.println("invoke result type: " + res.getClass().getName());
            System.out.println("invoke result: " + res);
            System.out.println("invoke result: " + JSON.toJSONString(res));
        } catch (ScriptException e) {
            throw new RuntimeException(e);
        } catch (FileNotFoundException e) {
            throw new RuntimeException(e);
        } catch (NoSuchMethodException e) {
            throw new RuntimeException(e);
        }
    }
}

输出：

invoke param: {"a":"def"}
invoke result type: com.oracle.truffle.polyglot.PolyglotMap
invoke result: {msg: JavaObject[com.alibaba.fastjson2.JSONObject]}
invoke result: {"msg":{"a":"def"}}