javascript - 从 javascript 内部抛出异常

Question

我有一个使用 Activiti 引擎的项目。它支持使用 Nashorn 运行脚本。我在脚本任务或任务监听器中运行此代码都没有问题。但是在使用执行监听器时我遇到了问题。

在我的脚本中，我想抛出一个应该被 java 代码捕获的错误。例如:

    throw new Error("this is an error");

但是我得到一个错误:

    problem evaluating script: Error: this is an error in scripts/error.js at line number 8 at column number 1

我最初也试过这个:

    var BpmnError = Java.type(org.activiti.engine.delegate.BpmnError');
    throw new BpmnError("BusinessExeptionOccured","a Message");

在这种情况下，没有错误被捕获，就好像抛出从未发生过一样。

在 Activiti 文档中它指出:

  As of Activiti 5.9, it is possible to throw BPMN Errors from user code inside Service Tasks or Script Tasks. In order to do this, a special ActivitiException called BpmnError can be thrown in JavaDelegates or scripts

我还没有找到任何例子来说明如何做到这一点。

我也没有看到任何可以抛出 jdk.nashorn.internal.runtime.ECMAException 的 JavaScript 代码示例opendJDK ECMAException 中的评论指出:

Exception used to implement ECMAScript "throw" from scripts. 

如有任何帮助，我们将不胜感激。

Answer 1

您可以捕获 ScriptException，然后从那里访问抛出的 ECMAScript 对象。

示例代码:

import javax.script.*;
import jdk.nashorn.api.scripting.*;

public class Main {
    public static void main(String[] args) throws Exception {
        ScriptEngineManager m = new ScriptEngineManager();
        ScriptEngine e = m.getEngineByName("nashorn");
        try {
            e.eval("throw new Error('this is an error');");
        } catch (ScriptException se) {
            // get the original cause
            Throwable cause = se.getCause();
            // in this case, the cause is a nashorn exception
            if (cause instanceof NashornException) {
                NashornException ne = (NashornException)cause;
                // Access the underlying ECMAScript error object thrown
                Object obj = ne.getEcmaError();
                // print ECMA object 'as is'
                System.out.println(obj);

                // In this example, the thrown ECMAScript object is
                // an instanceof Error. Script objects are accessible
                // as JSObject in java code.
                if (obj instanceof JSObject) {
                    JSObject jsObj = (JSObject)obj;
                    System.out.println(jsObj.getMember("message"));
                    System.out.println(jsObj.getMember("name"));
                    // access nashorn specific 'stack' property
                    System.out.println("stack trace: " + jsObj.getMember("stack"));
                }
            }
        }
    }
}