使用Nashorn JavaScript Engine（Java 8）访问ScriptContext的变量

Question

我将以下代码与RhinoJava中的JavaScript引擎一起使用：

@Test
public void testRhino() throws ScriptException {
    final ScriptEngineManager factory = new ScriptEngineManager();
    final ScriptEngine engine = factory.getEngineByName("rhino");
    final String raw = "I am the raw value injected";
    final ScriptContext ctx = new SimpleScriptContext();
    ctx.setAttribute("raw", raw, ScriptContext.ENGINE_SCOPE);

    String script = "var result = 'I am a result';";
    script += "java.lang.System.out.println(raw);";
    script += "'I am a returned value';";

    final Object res = engine.eval(script, ctx);
    System.out.println(ctx.getAttribute("result"));
    System.out.println(res);
}

脚本的输出（使用Rhino）为：

I am the raw value injected
I am a result
I am a returned value

在NashornJavaScript引擎中，我没有任何价值result：

@Test
public void testNashorn() throws ScriptException {
    final ScriptEngineManager factory = new ScriptEngineManager();
    final ScriptEngine engine = factory.getEngineByName("nashorn");
    final String raw = "I am the raw value injected";
    final ScriptContext ctx = new SimpleScriptContext();
    ctx.setAttribute("raw", raw, ScriptContext.ENGINE_SCOPE);

    String script = "var result = 'I am a result';";
    script += "java.lang.System.out.println(raw);";
    script += "'I am a returned value';";

    final Object res = engine.eval(script, ctx);
    System.out.println(ctx.getAttribute("result"));
    System.out.println(res);
}

退货

I am the raw value injected
null
I am a returned value

如何使用引擎访问result变量的值？ScriptContextnashorn

Answer 1

如果使用ScriptEngine.createEngine API创建ENGINE_SCOPE绑定，它将按预期工作：

import javax.script.*;

public class Main {
  public static void main(String[] args) throws Exception {

    final ScriptEngineManager factory = new ScriptEngineManager();
    final ScriptEngine engine = factory.getEngineByName("nashorn");
    final String raw = "I am the raw value injected";
    final ScriptContext ctx = new SimpleScriptContext();

    // **This is the inserted line**
    ctx.setBindings(engine.createBindings(), ScriptContext.ENGINE_SCOPE);

    ctx.setAttribute("raw", raw, ScriptContext.ENGINE_SCOPE);

    String script = "var result = 'I am a result';";
    script += "java.lang.System.out.println(raw);";
    script += "'I am a returned value';";

    final Object res = engine.eval(script, ctx);
    System.out.println(ctx.getAttribute("result"));
    System.out.println(res);
 }
}