readFully没有使用Java Nashorn Javascript Engine定义

发布时间：2020-12-15 00:59:10 所属栏目：Java 来源：网络整理

导读：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： eval:1 ReferenceError: "readFully" is not defined 该脚本使用readFully函数,该函数应在全局范围内定义nashorn在启用脚本模式的情况下运行(在通过ScriptEng

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：

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

该脚本使用readFully函数,该函数应在全局范围内定义nashorn在启用脚本模式的情况下运行(在通过ScriptEngine运行时默认为http://mail.openjdk.java.net/pipermail/nashorn-dev/2013-December/002562.html).

以下是重现错误的示例：

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);");


    }
}

这个样本打印嘿！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.但我有这个例外：

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,一切都很好.以下是相同脚本的结果：

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.

问候

解决方法

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

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;
}

（编辑：李大同）

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