Nashorn中的评估函数是否可从不同的线程重用？

Question

如果函数不改变任何共享对象，而是只使用调用中给出的参数，那么是否可以对所有servlet请求重用同一个Nashorn引擎和同一个JavaScriptObject（其结果是对JS函数的评估）？看下面的例子：

public class MyServlet extends HttpServlet {

private ScriptEngineManager factory;
private ScriptEngine engine;
private ScriptObjectMirror script;

@Override
public void init() throws ServletException {
    try {
        factory = new ScriptEngineManager();
        engine = factory.getEngineByName("nashorn");
        script = (ScriptObjectMirror)engine.eval("function(writer) {writer.print('Hello, World!');}");
    } catch (ScriptException ex) {
        Logger.getLogger(MyServlet.class.getName()).log(Level.SEVERE, null, ex);
    }
}

@Override
public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException {
    try (PrintWriter writer = res.getWriter()) {
        script.call(null, writer);
        writer.close();
    } catch (IOException ex) {
        Logger.getLogger(MyServlet.class.getName()).log(Level.SEVERE, null, ex);
    }
}

这个线程安全吗？这是在Servlet中重用Nashorn ScriptEngine的后续

编辑：我不确定这对手头的问题有什么不同，但是为了关注更有趣的问题，在这种情况下，对一个已计算的js函数的调用是线程保存，我现在把所有字段都变成了最终的。所以代码是：

public class MyServlet extends HttpServlet {

final private ScriptEngineManager factory;
final private ScriptEngine engine;
final private ScriptObjectMirror script;

public MyServlet() {
    factory = new ScriptEngineManager();
    engine = factory.getEngineByName("nashorn");
    ScriptObjectMirror _script = null;
    try {
        _script = (ScriptObjectMirror) engine.eval("function(writer) {writer.print('Hello, World!');}");
    } catch (ScriptException ex) {
        Logger.getLogger(MyServlet.class.getName()).log(Level.SEVERE, null, ex);
    }
    script = _script;
}

@Override
public void init() throws ServletException {
}

@Override
public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException {
    try (PrintWriter writer = res.getWriter()) {
        script.call(null, writer);
        writer.close();
    } catch (IOException ex) {
        Logger.getLogger(MyServlet.class.getName()).log(Level.SEVERE, null, ex);
    }
}

Answer 1

没有一个实例变量是安全发布的，所以这是一个很大的“否”。此外，没有任何文档说明您使用的类是线程安全的，因此如果没有其他文档说明，您必须假设它们不是线程安全的。

回答：没有。