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尝试使Nashorn线程安全

javaplayframeworkplayframework-2.0nashorn
3

我最近使用Play!框架和Nashorn尝试渲染Redux应用程序。最初，我在ThreadPoolExecutor中实现了多个Nashorn引擎，并在运行 engine.eval() 时使用futures。性能非常糟糕，我认为这是由于高I/O和我使用的阻塞future造成的。

在更加熟悉Play!和他们的异步/承诺模式之后，我尝试重新启动，只使用单个ScriptEngine；根据 https://dev59.com/YF0a5IYBdhLWcg3wmZsX#30159424，脚本引擎本身是线程安全的，但绑定不是。以下是完整的类：

package services;

import akka.actor.ActorSystem;

import play.libs.F;
import scala.concurrent.ExecutionContext;

import java.io.FileReader;


import javax.inject.Inject;
import javax.inject.Singleton;
import javax.script.*;

@Singleton
public class NashornEngine extends JSEngineAbstract {

    private NashornThread engine;
    private final ActorSystem actorSystem;


    protected class NashornThread {
        private ScriptEngine engine;
        private final ExecutionContext executionContext = actorSystem.dispatchers().lookup("js-engine-executor");
        private CompiledScript compiledScript;


        public NashornThread() {
            try {
                String dir = System.getProperty("user.dir");
                this.engine = new ScriptEngineManager(null).getEngineByName("nashorn");
                this.compiledScript = ((Compilable) this.engine).compile(new FileReader(dir + "/public/javascripts/bundle.js"));
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }
        }

        public ScriptEngine getEngine() {
            return engine;
        }

        public F.Promise<String> getContent(String path, String globalCode) {
            return F.Promise.promise(() -> this.executeMethod(path, globalCode), this.executionContext);
        }

        private String executeMethod(String path, String json) throws ScriptException {
            Bindings newBinding = engine.createBindings();
            try {
                this.compiledScript.eval(newBinding);
                getEngine().setBindings(newBinding, ScriptContext.ENGINE_SCOPE);
                getEngine().eval("var global = this;");
                getEngine().eval("var console = {log: print, error: print, warn: print};");
                String result = getEngine().eval("App.renderApp('" + path + "', " + json + ")").toString();

                return result;
            } catch(Exception e) {
                e.printStackTrace();
                return null;
            }
        }
    }


    @Inject
    public NashornEngine(ActorSystem actorSystem) {
        this.actorSystem = actorSystem;
        this.engine = new NashornThread();
    }

    @Override
    public F.Promise<String> getContent(String path, String globalCode) {
        try {
            F.Promise<String> result = engine.getContent(path, globalCode);

            return result.map((String r) -> r);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
}

我的JavaScript应用程序导出一个名为App的对象，该对象有一个可见的renderApp(path, state)方法。实际上这确实可以工作，但只能工作16次（是的，总是16次）。从第17次迭代开始，我会得到以下异常和其中的堆栈跟踪：
java.lang.ClassCastException: jdk.nashorn.internal.objects.NativeRegExpExecResult cannot be cast to jdk.nashorn.internal.objects.NativeArray
    at jdk.nashorn.internal.objects.NativeArray.getContinuousArrayDataCCE(NativeArray.java:1900)
    at jdk.nashorn.internal.objects.NativeArray.popObject(NativeArray.java:937)
    at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:660)
    at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:228)
    at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:393)
    at jdk.nashorn.internal.scripts.Script$Recompilation$23589$782286AA$\^eval\_.L:22918$L:22920$matchPattern(<eval>:23049)
    at jdk.nashorn.internal.scripts.Script$Recompilation$23588$816752AAAAAA$\^eval\_.L:24077$L:24079$matchRouteDeep(<eval>:24168)
    at jdk.nashorn.internal.scripts.Script$Recompilation$23587$820262DAA$\^eval\_.L:24077$L:24079$matchRoutes$L:24252$L:24253(<eval>:24254)
    at jdk.nashorn.internal.scripts.Script$Recompilation$23586$809060$\^eval\_.L:23848$loopAsync$next(<eval>:23869)
    at jdk.nashorn.internal.scripts.Script$Recompilation$23584$808906AAA$\^eval\_.L:23848$loopAsync(<eval>:23875)
    at jdk.nashorn.internal.scripts.Script$Recompilation$23583$820189$\^eval\_.L:24077$L:24079$matchRoutes$L:24252(<eval>:24253)
    at jdk.nashorn.internal.scripts.Script$Recompilation$23582$819862AAA$\^eval\_.L:24077$L:24079$matchRoutes(<eval>:24252)
    at jdk.nashorn.internal.scripts.Script$Recompilation$23580$789440AA$\^eval\_.L:23151$L:23153$useRoutes$L:23209$match(<eval>:23239)
    at jdk.nashorn.internal.scripts.Script$Recompilation$23518$847004AA$\^eval\_.L:25026$L:25028$match(<eval>:25084)
    at jdk.nashorn.internal.scripts.Script$Recompilation$23468$3872AA$\^eval\_.L:53$renderApp(<eval>:147)
    at jdk.nashorn.internal.scripts.Script$23467$\^eval\_.:program(<eval>:1)
    at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:640)
    at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:228)
    at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:393)
    at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:446)
    at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:403)
    at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:399)
    at jdk.nashorn.api.scripting.NashornScriptEngine.eval(NashornScriptEngine.java:155)
    at javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:264)
    at services.NashornEngine$NashornThread.executeMethod(NashornEngine.java:62)
    at services.NashornEngine$NashornThread.lambda$getContent$0(NashornEngine.java:48)
    at play.core.j.FPromiseHelper$$anonfun$promise$2.apply(FPromiseHelper.scala:36)
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)
    at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:40)
    at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:397)
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

我认为使用编译后的脚本创建一个新的绑定会被视为对引擎的全新修改，但实际情况并非如此。我在这里做错了什么？
我尝试使用Invocable调用App对象上的方法，但结果没有任何改变。
编辑： 我的机器是8核心带超线程，这可能解释了为什么前16次尝试都成功而第17次失败了。另外，我已更新executeMethod方法如下：
private String executeMethod(String path, String json) throws ScriptException {
            Bindings newBinding = engine.createBindings();
            try {
                this.compiledScript.eval(newBinding);
                getEngine().eval("var global = this;", newBinding);
                getEngine().eval("var console = {log: print, error: print, warn: print};", newBinding);
                Object app = getEngine().eval("App", newBinding);
                Invocable invEngine = (Invocable) getEngine();
                String result = invEngine.invokeMethod(app, "renderApp", path, json).toString();
//              String result = getEngine().eval("App.renderApp('" + path + "', " + json + ")", newBinding).toString();

                return result;
            } catch(Exception e) {
                e.printStackTrace();
                return null;
            }
        }
2个回答
2

更新到最新版本的Nashorn，或者Java 1.8u76可以解决这个问题。

1
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