为什么getEngineByName("js")返回null? [英] Why does getEngineByName(“js”) return null?

问题描述

无论我尝试什么，getEngineByName()都将继续返回null.

Whatever I try, getEngineByName() keeps returning null.

这是我的代码:

final ScriptEngineManager manager = new ScriptEngineManager();
final ScriptEngine engine = manager.getEngineByName("js");

但是engine在这些行之后为空.

But engine is null after these lines.

我也尝试过:

• getEngineByName("javascript")
• getEngineByName("nashorn")

• getEngineByName("javascript")
• getEngineByName("nashorn")

它们都返回null.实际上，manager.getEngineFactories()显示的是一个空数组-意味着根本没有工厂.

They all return null. Actually, manager.getEngineFactories() shows an empty array - meaning there are no Factories at all.

这2个答案建议将null传递给构造函数，但这对我不起作用:

These 2 answers suggest passing null to the constructor, but it didn't work for me:

• https://stackoverflow.com/a/25332851/900394
• https://stackoverflow.com/a/25332851/900394

• https://stackoverflow.com/a/25332851/900394
• https://stackoverflow.com/a/25332851/900394

这个答案说的是已修复的错误.

更新:

那是Eclipse中的 Android应用项目.

That was an Android Application Project in eclipse.

我不知道它与 Java项目有什么不同.

I didn't know it differs that much from a Java Project.

现在，我刚刚打开一个新的 Java项目，并写了以下几行，然后得到了一些结果:

Now I just opened a new Java Project, wrote these lines, and I'm getting some results:

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import javax.script.SimpleBindings;

public class TestClass {

    public static void main(String[] args) throws ScriptException {
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = scriptEngineManager.getEngineByName("js");
    }
}

engine不是空！

此外，javax.script.*已成功导入，就好像它已经存在(内置)一样.这是因为我正在使用Java 8吗?

Also, javax.script.* was imported successfully as if it's already there (built in). Is this because I'm using Java 8?

在先前的(android)项目中，我使用的是 javax.script ，该软件是从

In that previous (android) project I was using javax.script downloaded from here.

那么 Android项目中会出现什么问题，我该如何解决?

So what would be the problem in the Android Project and how do I solve it?

推荐答案

您必须使用大写字母写参数，如下所示:

You have to write the argument with Capital Letters, as shown below:

getEngineByName("JavaScript");
                 ^   ^

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