readFully没有使用Java Nashorn Javascript Engine定义 [英] readFully not defined with Java Nashorn Javascript Engine

问题描述

我正在尝试使用新的Java 8 Nashorn javascript引擎运行javascript脚本，但它失败并出现以下错误：

I am trying to run a javascript script with the new Java 8 Nashorn javascript engine but it fails with the following error:

<eval>:1 ReferenceError: "readFully" is not defined

该脚本使用readFully函数应该在全局范围内定义nashorn是在启用脚本模式的情况下运行的（在通过ScriptEngine运行时是默认的 http://mail.openjdk.java.net/pipermail/nashorn-dev/2013-December/002562.html 。

The script uses the readFully function that should be defined in the global scope nashorn is run with the scripting mode enabled (wich is default when running through a ScriptEngine as seen here http://mail.openjdk.java.net/pipermail/nashorn-dev/2013-December/002562.html).

以下是重现错误的示例：

Here is a sample to reproduce the error:

import java.io.FileNotFoundException;

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

public class Test {

    public static void main(String[] argv) throws FileNotFoundException, ScriptException {
        ScriptEngine scriptEngine = new ScriptEngineManager().getEngineByName("nashorn");

        scriptEngine.eval("print('Hey!');print(print);print(readFully);");


    }
}

此样本打印嘿！然后是print函数的源代码（另一个nashorn内置函数），最后它应该打印readFully方法的源代码。但是我有这个例外：

This sample prints Hey ! and then the source code of the print function (another nashorn built-in function) and finally it should print the source code of the readFully method. But I have this Exception instead:

Exception in thread "main" javax.script.ScriptException: ReferenceError: "readFully" is not defined in <eval> at line number 1
    at jdk.nashorn.api.scripting.NashornScriptEngine.throwAsScriptException(NashornScriptEngine.java:586)
    at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:570)
    at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:525)
    at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:521)
    at jdk.nashorn.api.scripting.NashornScriptEngine.eval(NashornScriptEngine.java:192)
    at javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:264)
    at com.github.bringking.maven.requirejs.Test.main(Test.java:14)
Caused by: <eval>:1 ReferenceError: "readFully" is not defined
    at jdk.nashorn.internal.runtime.ECMAErrors.error(ECMAErrors.java:58)
    at jdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:320)
    at jdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:292)
    at jdk.nashorn.api.scripting.NashornScriptEngine.__noSuchProperty__(NashornScriptEngine.java:272)
    at jdk.nashorn.internal.scripts.Script$engine.L:35(nashorn:engine/resources/engine.js:37)
    at jdk.nashorn.internal.scripts.Script$\^eval\_.runScript(<eval>:1)
    at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:535)
    at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:209)
    at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:378)
    at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:568)
    ... 5 more

当使用带有-scripting参数的nashorn命令行（使用jdk的jjs工具）运行示例脚本时，一切正常。以下是相同脚本的结果：

When the sample script is run with the nashorn command line with the -scripting parameter (with the jjs tool of the jdk), all is fine. Here is the result of the same script:

Hey!
function print() { [native code] }
function readFully() { [native code] }

我可以重写一个readFully方法并将其与脚本上下文绑定，但我更喜欢理解为什么它不起作用并使用已经内置的函数。

I could rewrite a readFully method and bind it with the script context, but I prefer to understand why it does not work and use already built-in functions.

问候

推荐答案

最后，我实现了一个我在脚本中使用的readFully函数（仅与Nashorn兼容） ：

Finally, I have implemented a readFully function that I use in my script (Only compatible with Nashorn):

function readFully(url) {
    var result = "";
    var imports = new JavaImporter(java.net, java.lang, java.io);

    with (imports) {

        var urlObj = null;

        try {
            urlObj = new URL(url);
        } catch (e) {
            // If the URL cannot be built, assume it is a file path.
            urlObj = new URL(new File(url).toURI().toURL());
        }

        var reader = new BufferedReader(new InputStreamReader(urlObj.openStream()));

        var line = reader.readLine();
        while (line != null) {
            result += line + "\n";
            line = reader.readLine();
        }

        reader.close();
    }

    return result;
}

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